{"gene":"FEN1","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":1994,"finding":"FEN-1 is a structure-specific endonuclease that cleaves DNA flap structures (5' flap and pseudo Y-structures); the murine FEN-1 gene was cloned and shown to be homologous to S. cerevisiae YKL510 (RAD27) and RAD2. YKL510 and a truncated RAD2 protein were also demonstrated to be structure-specific endonucleases with similar substrate specificity.","method":"Gene cloning, in vitro nuclease assays with branched DNA substrates","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro enzymatic characterization with defined substrates, replicated across multiple homologs","pmids":["7926735"],"is_preprint":false},{"year":1995,"finding":"FEN-1 binding and cleavage of flap DNA structures requires the adjacent (Fadj) strand that provides a double-stranded template near the elbow of the flap; absence or recession of this strand dramatically reduces binding efficiency. FEN-1 possesses both 5'-flap endonuclease and double-stranded DNA 5'-exonuclease activity within the same 42 kDa enzyme.","method":"Mobility shift assay, in vitro nuclease assays with defined DNA substrates","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro binding and cleavage assays with multiple substrate variants, single lab but multiple orthogonal methods","pmids":["7876218"],"is_preprint":false},{"year":1996,"finding":"Human PCNA physically associates with human FEN-1 and stimulates its endonucleolytic activity at branched DNA (flap) structures and its exonucleolytic activity at nick and gap structures. PCNA loads onto substrates at double-stranded DNA ends, while FEN-1 loads by tracking along the single-stranded DNA branch from its free 5' terminus.","method":"Physical association (co-purification/interaction assays), in vitro nuclease stimulation assays with defined DNA substrates","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — physical interaction plus functional stimulation demonstrated in vitro, replicated and extended by subsequent structural studies","pmids":["8668533"],"is_preprint":false},{"year":1996,"finding":"FEN-1 (RAD2 homologue 1) tracks along the single-stranded 5' tail of a flap substrate from its 5' end to the cleavage point, protecting a ~25 nucleotide region adjacent to the cleavage site, and can cleave past adducts (CDDP) located within or beyond the protected region, but is inhibited by an adduct immediately adjacent to the cleavage point.","method":"Micrococcal nuclease footprinting, in vitro cleavage assays with site-specifically adducted DNA substrates","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct mechanistic footprinting and cleavage assays, single lab","pmids":["8939893"],"is_preprint":false},{"year":1999,"finding":"DNA secondary structures formed at trinucleotide repeat sequences (CAG, CGG, CTG) inhibit FEN-1 cleavage in a length-dependent manner by concealing the 5' end of the flap required for FEN-1 binding and cleavage, providing a mechanism for repeat expansion.","method":"In vitro FEN-1 cleavage assays with repeat-containing flap substrates; genetic studies in yeast lacking FEN-1","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — biochemical reconstitution with defined substrates plus genetic validation, single lab with two orthogonal approaches","pmids":["10635332"],"is_preprint":false},{"year":1999,"finding":"Deletion of RAD27 (yeast FEN-1) leads to a 4.4-fold reduction specifically in NHEJ events predicted to proceed via 5' flap intermediates, establishing a role for FEN-1 in non-homologous DNA end joining through processing of 5' flap structures that arise after end alignment.","method":"Genetic epistasis in S. cerevisiae; NHEJ assay with specific substrates in rad27 deletion strains","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with defined substrate specificity, single lab","pmids":["9990019"],"is_preprint":false},{"year":2000,"finding":"FEN1 interacts with PCNA through two distinct modes: in solution (without DNA), FEN1 binds primarily through the PCNA interdomain connector loop (IDCL); when PCNA encircles DNA, the C-terminal domain of PCNA (not the IDCL) is critical for FEN1 binding and stimulation of activity. An FF→GA mutation in FEN1's PCNA-interaction domain abolishes both modes and causes replication and repair defects in vivo.","method":"Yeast genetics with PCNA mutants (pcna-79, pcna-90), DNA-bead retention assay, FEN1 mutagenesis, in vivo complementation","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple PCNA and FEN1 mutants tested with biochemical and genetic assays, single lab with orthogonal methods","pmids":["10899134"],"is_preprint":false},{"year":2002,"finding":"WRN protein physically interacts with FEN-1 and stimulates its cleavage activity by enhancing catalytic efficiency rather than DNA substrate binding. WRN stimulates FEN-1 on multiple Okazaki fragment processing intermediates including flaps with terminal monoribonucleotides, long 5' ssDNA tracts, and pseudo-Y structures, and does so even when a free upstream end is blocked (unlike PCNA-mediated stimulation).","method":"Biochemical kinetics of FEN-1 cleavage in the presence/absence of WRN, substrate binding assays, streptavidin-blocked substrate experiments","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinetic characterization with multiple substrates and mechanistic controls, single lab","pmids":["12356323"],"is_preprint":false},{"year":2003,"finding":"C. elegans CRN-1 (FEN-1 homolog) cooperates with CPS-6/EndoG to promote apoptotic DNA degradation. CRN-1 utilizes its 5'-3' exonuclease activity and a newly identified gap-dependent endonuclease (GEN) activity together with CPS-6 endonuclease activity for stepwise DNA fragmentation during apoptosis.","method":"RNAi knockdown in C. elegans, genetic interaction with cps-6 mutant, biochemical characterization of GEN activity","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo genetic epistasis plus biochemical identification of novel GEN activity, single lab with multiple orthogonal methods","pmids":["12840007"],"is_preprint":false},{"year":2004,"finding":"Crystal structures of FEN-1:DNA and PCNA:FEN-1-peptide complexes reveal that FEN-1 binds the unpaired 3' DNA end (3' flap), opens and kinks DNA, and promotes conformational closing of a flexible helical clamp to facilitate 5' cleavage specificity. Ordering of unstructured C-terminal regions in FEN-1 and PCNA creates an intermolecular beta-sheet interface directly linking PCNA and DNA binding regions of FEN-1. FRET and mutagenesis support a kinked DNA pivot point for coordinated handoffs.","method":"X-ray crystallography, FRET, site-directed mutagenesis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures plus FRET and mutagenesis in a single rigorous study, multiple orthogonal methods","pmids":["14718165"],"is_preprint":false},{"year":2004,"finding":"In S. cerevisiae NHEJ, FEN-1 (Rad27) physically and functionally interacts with Pol4 and Dnl4/Lif1, and together these proteins coordinately process and join DNA molecules with incompatible 5' ends, establishing a series of pairwise interactions that complete DSB repair by NHEJ.","method":"Physical interaction assays (co-immunoprecipitation/pulldown), in vitro end-joining reconstitution with defined substrates","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — physical and functional interaction demonstrated in vitro with multiple proteins, single lab","pmids":["15342630"],"is_preprint":false},{"year":2005,"finding":"FEN-1-deficient chicken DT40 cells show decreased efficiency of immunoglobulin gene conversion (HR between divergent sequences) but are proficient in sister chromatid recombination, indicating FEN-1 eliminates heterologous sequences at DNA break sites to facilitate HR. This was confirmed by I-SceI-induced DSB experiments with divergent donor/recipient substrates.","method":"Gene knockout in chicken DT40 cells, I-SceI-induced recombination assays, gene conversion frequency measurement","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with specific phenotypic readouts and mechanistic substrate manipulation, single lab","pmids":["16055708"],"is_preprint":false},{"year":2006,"finding":"FEN-1's gap endonuclease (GEN) activity uses the same clamp region that FEN activity uses to interact with single-stranded DNA substrates. The C-terminal extension of human FEN-1 likely interacts with the downstream duplex in all substrate types, and GEN activity in complex with WRN can cleave hairpin and internal loop substrates, suggesting a role in preventing repeat expansions.","method":"Kinetic analysis of FEN, EXO, and GEN activities; DNA-binding deficient FEN1 mutants; biochemical assays with WRN","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — comparative kinetics with multiple mutants and substrates, single lab with two orthogonal methods","pmids":["16582103"],"is_preprint":false},{"year":2008,"finding":"FEN1 is present in human mitochondria (confirmed by protease protection of mitochondria, immunofluorescence, and subcellular fractionation) and participates in long-patch base excision repair (LP-BER) of oxidized abasic sites (2-deoxyribonolactone) in mitochondrial DNA. Immunodepletion of FEN1 from mitochondrial extracts strongly diminishes LP-BER activity.","method":"Subcellular fractionation, immunofluorescence, protease protection assay, immunodepletion of mitochondrial extracts, RNAi knockdown with damage recovery assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal localization and functional methods, immunodepletion directly linking FEN1 to LP-BER activity in mitochondria","pmids":["18541666"],"is_preprint":false},{"year":2009,"finding":"FEN1 promotes CAG repeat expansion during long-patch BER by facilitating ligation of hairpins formed by strand slippage, resulting from uncoupling of normal pol beta–FEN1 coordination during multinucleotide gap-filling synthesis. HMGB1 promotes expansion by stimulating APE1 and FEN1.","method":"In vitro reconstitution of repeat expansion using mouse cell extracts; biochemical assays dissecting individual enzyme contributions","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — biochemical reconstitution in cell extracts with defined substrates, single lab","pmids":["19674974"],"is_preprint":false},{"year":2010,"finding":"FEN1 is methylated at arginine residues (primarily Arg192) by an arginine methyltransferase; this methylation suppresses phosphorylation at Ser187. The methylated form (but not the phosphorylated form) strongly interacts with PCNA, ensuring proper timing of FEN1 activity. Mutations disrupting arginine methylation cause unscheduled phosphorylation, failure to localize to DNA replication/repair foci, defects in Okazaki fragment maturation, cell cycle delay, impaired DNA repair, and elevated genome-wide mutation rates.","method":"Mass spectrometry identification of methylation sites, site-directed mutagenesis, co-immunoprecipitation with PCNA, immunofluorescence localization, cell cycle analysis","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — MS identification plus mutagenesis plus interaction studies plus localization and functional readouts, multiple orthogonal methods","pmids":["20729856"],"is_preprint":false},{"year":2010,"finding":"FEN1 is required for efficient replication fork re-initiation at telomeres. FEN1 gap endonuclease activity (not Okazaki fragment processing activity) and the FEN1 interaction with RecQ helicases are vital for telomere stability, as FEN1 depletion causes fragile telomere expression and sister telomere loss.","method":"FEN1 siRNA depletion, fragile telomere and sister telomere loss assays, functional dissection using FEN1 activity mutants","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with mechanistic dissection using activity-specific mutants, single lab","pmids":["20551483"],"is_preprint":false},{"year":2011,"finding":"Crystal structures and functional analyses of human FEN1:DNA complexes reveal structure-specific, sequence-independent recognition: FEN1 binds nicked dsDNA bent ~100° with unpaired 3' and 5' flaps. A helical cap over a gateway formed by two helices enforces ssDNA threading and specificity for free 5' ends. Double-base unpairing flanking the scissile phosphate and the two-metal-ion active site control precise flap incision.","method":"X-ray crystallography of FEN1:DNA product and substrate complexes, mutagenesis, functional assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple crystal structures plus mutagenesis, comprehensive mechanistic study in single rigorous publication","pmids":["21496641"],"is_preprint":false},{"year":2011,"finding":"A FEN1 point mutation (F343A/F344A, FFAA) that specifically abolishes the FEN1/PCNA interaction causes defects in RNA primer removal and long-patch BER, resulting in DNA breaks, G2/M checkpoint activation (via Chk1), near-tetraploid aneuploidy, elevated cellular transformation frequency, and cancer in knock-in mice.","method":"Knock-in mouse model, biochemical assays for BER and Okazaki fragment processing, cytogenetic analysis, transformation assays","journal":"Cell research","confidence":"High","confidence_rationale":"Tier 2 / Strong — knock-in mouse model with multiple orthogonal readouts directly linking a specific protein-protein interaction to mechanistic consequences","pmids":["21383776"],"is_preprint":false},{"year":2012,"finding":"FEN1 undergoes sequential post-translational modifications controlling its proteasomal degradation: phosphorylation stimulates SUMOylation, which in turn stimulates ubiquitination and proteasomal degradation. Blocking any step in this cascade suppresses FEN1 degradation and causes accumulation of Cyclin B, G1/G2M phase delays, and polyploidy.","method":"Biochemical characterization of PTMs, mutant FEN1 expression, cell cycle analysis, proteasome inhibitor experiments","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — sequential PTM cascade dissected with multiple mutants and inhibitors, single lab with multiple orthogonal methods","pmids":["22749529"],"is_preprint":false},{"year":2012,"finding":"FEN1 forms a complex with the checkpoint clamp Rad9-Hus1-Rad1 (9-1-1) in addition to PCNA. The 9-1-1/FEN1/DNA assembly has greater stability than the PCNA/FEN1/DNA complex, as determined by 3D electron microscopy reconstruction at 18-Å resolution combined with molecular dynamics simulations, consistent with distinct roles in DNA repair versus replication.","method":"Single-particle electron microscopy, molecular dynamics simulations, computational modeling","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — EM structure of ternary complex plus MD simulations, single study with structural and computational methods","pmids":["22586102"],"is_preprint":false},{"year":2012,"finding":"Endogenous FEN1-YFP rapidly accumulates at local laser-induced DNA damage sites in living cells. PARP1 inhibition disrupts FEN1 accumulation at DNA repair intermediates, establishing that PARP1 is required for FEN1 recruitment to BER sites.","method":"Fluorescent knock-in mouse model (FEN1-YFP), live-cell multi-photon fluorescence microscopy, PARP1 inhibitor treatment","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — endogenous tagged protein in living cells/tissues, direct PARP1 dependency demonstrated, multiple orthogonal methods","pmids":["22810208"],"is_preprint":false},{"year":2014,"finding":"The FEN1 E359K germline mutation abolishes the FEN1-WRN interaction (critical for resolving stalled replication forks) and eliminates FEN1 gap-dependent endonuclease (GEN) activity while leaving flap endonuclease activity intact. E359K mouse embryonic fibroblasts are hypersensitive to DNA crosslinking agents, show fragile telomeres and increased chromosomal anomalies, and E359K homozygous mice develop cancer at high frequency.","method":"Knock-in mouse model, co-immunoprecipitation, in vitro biochemical activity assays, cytogenetic analysis, tumor incidence measurement","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — knock-in mouse model with biochemical dissection of specific interaction and activity, multiple orthogonal methods","pmids":["24608430"],"is_preprint":false},{"year":2013,"finding":"Single-molecule FRET and protein-induced fluorescence enhancement studies reveal that upon FEN1 binding, a flap DNA substrate is bent and locked into an open flap conformation. PCNA enhances FEN1 recognition by further promoting the open flap conformation, likely by facilitating threading of the 5' ssDNA flap through the helical gateway.","method":"Single-molecule FRET, protein-induced fluorescence enhancement, ensemble FRET","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — single-molecule biophysics with multiple methods, single lab","pmids":["24234453"],"is_preprint":false},{"year":2016,"finding":"The cancer-associated FEN1 L209P mutation abolishes FEN, EXO, and GEN nuclease activities but retains DNA-binding affinity, acting in a dominant-negative manner to impair wild-type FEN1 function and long-patch BER in vitro and in vivo, leading to genomic instability and cellular transformation.","method":"Biochemical activity assays, DNA binding assays, dominant-negative expression in cells, in vitro BER assays, mouse xenograft","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical characterization plus cellular and in vivo validation, single lab with multiple methods","pmids":["27270424"],"is_preprint":false},{"year":2019,"finding":"FEN1 participates in microhomology-mediated end-joining (MMEJ); BRCA2-deficient cells require specifically the 5' flap endonuclease activity (not the 5'-3' exonuclease activity) of FEN1, and chemical inhibition of FEN1 selectively targets BRCA-deficient cells.","method":"CRISPR-based genetic screens in isogenic BRCA2-deficient cell lines, MMEJ reporter assay, FEN1 activity-specific mutants, small-molecule FEN1 inhibitor","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide screens validated with MMEJ reporter and activity-specific dissection, multiple orthogonal approaches","pmids":["30686591"],"is_preprint":false},{"year":2019,"finding":"FEN1 promotes breast cancer cell proliferation via formation of a FEN1/PCNA/DNMT3a complex that suppresses miR-200a-5p expression through DNA methylation, thereby allowing expression of miR-200a target genes MET and EGFR.","method":"Co-immunoprecipitation (FEN1-PCNA-DNMT3a complex), luciferase reporter (miR-200a target sites), methylation-specific PCR, siRNA knockdown","journal":"FASEB journal","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP for complex; epigenetic mechanism supported by reporter assay but limited mechanistic validation, single lab","pmids":["31266372"],"is_preprint":false},{"year":2020,"finding":"IGF2BP2 directly recognizes and binds the m6A site on FEN1 mRNA, enhancing FEN1 mRNA stability and thereby maintaining FEN1 protein expression in HCC cells.","method":"RNA immunoprecipitation (RIP), m6A site mapping, IGF2BP2 overexpression/knockdown with FEN1 mRNA stability measurement","journal":"Frontiers in oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — RIP assay with mRNA stability measurement, post-transcriptional regulation of FEN1, single lab single method","pmids":["33224879"],"is_preprint":false},{"year":2020,"finding":"FEN1 blockade induces proteasome-mediated degradation of activated ERα and loss of ERα-driven gene expression. FEN1 facilitates coactivator recruitment to the ERα transcriptional complex, thereby impacting ERα transcriptional activity and driving tumor cell proliferation in tamoxifen-resistant breast cancer.","method":"FEN1 siRNA depletion, ERα co-immunoprecipitation/coactivator recruitment assays, proteasome inhibitor rescue, small-molecule FEN1 inhibitor screen, proliferation assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple cell-based methods demonstrating FEN1-ERα interaction and functional consequence, independently supported by inhibitor studies","pmids":["32193286"],"is_preprint":false},{"year":2020,"finding":"PRMT1 methylates FEN1 as a post-translational modification, maintaining high FEN1 expression levels critical for DNA repair and chemotherapeutic drug resistance in lung cancer cells.","method":"PRMT1 knockdown with FEN1 protein level measurement, identification of FEN1 as PRMT1 substrate by co-immunoprecipitation","journal":"DNA repair","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single co-IP for substrate identification with knockdown, limited mechanistic detail in abstract, single lab","pmids":["32861926"],"is_preprint":false},{"year":2011,"finding":"FEN1 regulates cell survival, MAPK p38 phosphorylation, RhoA activation, and actin cytoskeleton reorganization in response to DNA damage triggered by bacterial CDT genotoxin, revealing a crosstalk between DNA damage response and cytoskeleton dynamics mediated by FEN1.","method":"S. cerevisiae mutant screen, human cell FEN1 siRNA knockdown, RhoA activation assay, p38 phosphorylation measurement, actin cytoskeleton imaging","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast genetic screen validated in human cells with multiple phenotypic readouts, single lab","pmids":["21807938"],"is_preprint":false},{"year":2005,"finding":"p53 transcriptionally activates FEN1 expression via a p53 consensus binding site in the fen1 promoter. FEN1 induction by UV-C requires p53 and replication-competent cells. Transgenic FEN1 expression in p53-null cells attenuates UV-C-induced DNA replication inhibition, establishing FEN1 as involved in recovery from stalled replication forks downstream of p53.","method":"RT-PCR, Western blot, promoter cloning and reporter assays, ChIP (p53 binding to fen1 promoter), transgenic FEN1 expression in p53-null cells, DNA replication recovery assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter binding demonstrated by reporter and cotransfection with functional rescue, single lab with multiple orthogonal methods","pmids":["16103874"],"is_preprint":false}],"current_model":"FEN1 is a structure-specific endo/exonuclease that recognizes and cleaves 5' flap DNA intermediates by threading the free 5' ssDNA through a helical gateway above its two-metal-ion active site while bending the dsDNA ~100°; it functions in Okazaki fragment maturation, long-patch base excision repair (including in mitochondria), stalled replication fork rescue, telomere maintenance, NHEJ, MMEJ, and apoptotic DNA fragmentation, and is regulated by sequential post-translational modifications (arginine methylation suppresses phosphorylation to promote PCNA binding; phosphorylation→SUMOylation→ubiquitination drives proteasomal degradation) as well as by protein partners including PCNA (via two distinct binding modes), WRN, RecQ helicases, the 9-1-1 checkpoint clamp, PARP1 (for recruitment to BER sites), and Dnl4/Lif1/Pol4 in NHEJ."},"narrative":{"mechanistic_narrative":"FEN1 is a structure-specific, sequence-independent nuclease that recognizes, threads, and cleaves 5' flap DNA intermediates, serving as a central enzyme in DNA replication and repair [PMID:7926735, PMID:21496641]. It carries flap endonuclease, 5'-3' double-stranded exonuclease, and gap-dependent endonuclease (GEN) activities within a single ~42 kDa enzyme [PMID:7876218, PMID:16582103]. Substrate engagement requires the duplex template adjacent to the flap, and the enzyme tracks along the free single-stranded 5' tail to the cleavage point [PMID:7876218, PMID:8939893]. Crystallographic and biophysical studies define a mechanism in which FEN1 binds and bends nicked dsDNA ~100°, captures the unpaired 3' flap, and threads the 5' ssDNA through a helical gateway/cap so that double-base unpairing at the scissile phosphate positions it over a two-metal-ion active site for precise incision [PMID:14718165, PMID:21496641, PMID:24234453]. Through these activities FEN1 performs Okazaki fragment maturation and long-patch base excision repair, including LP-BER of oxidized abasic lesions in mitochondrial DNA, and contributes to stalled replication fork rescue, telomere maintenance, NHEJ, microhomology-mediated end joining, homologous recombination, and apoptotic DNA fragmentation [PMID:9990019, PMID:12840007, PMID:18541666, PMID:20551483, PMID:30686591]. FEN1 is coordinated by partner proteins: PCNA stimulates its activity and promotes the open-flap conformation through two distinct binding modes, while WRN, RecQ helicases, and the 9-1-1 (Rad9-Hus1-Rad1) checkpoint clamp form alternative complexes that direct repair versus replication functions, and PARP1 is required for FEN1 recruitment to BER sites [PMID:8668533, PMID:10899134, PMID:20551483, PMID:22586102, PMID:22810208, PMID:24234453]. FEN1 activity is timed by sequential post-translational modifications: arginine methylation (Arg192) suppresses Ser187 phosphorylation to favor PCNA binding, whereas an ordered phosphorylation→SUMOylation→ubiquitination cascade drives its proteasomal degradation [PMID:20729856, PMID:22749529]. Loss or mutation of FEN1 causes genomic instability, aneuploidy, and cancer: disruption of the FEN1-PCNA interaction or of the FEN1-WRN interaction (E359K, ablating GEN activity) produces fragile telomeres, chromosomal anomalies, and tumors in knock-in mice, and inhibition of FEN1 selectively kills BRCA-deficient cells [PMID:21383776, PMID:24608430, PMID:30686591].","teleology":[{"year":1994,"claim":"Established the foundational identity of FEN1 as a structure-specific endonuclease conserved across species, answering what kind of DNA structures it acts on.","evidence":"Gene cloning and in vitro nuclease assays on branched substrates, with conservation to yeast RAD27/RAD2","pmids":["7926735"],"confidence":"High","gaps":["Catalytic mechanism and metal dependence not yet defined","In vivo pathway roles not yet assigned"]},{"year":1995,"claim":"Defined the substrate determinants of flap recognition and showed both endo- and exonuclease activities reside in one enzyme, clarifying how FEN1 selects its targets.","evidence":"Mobility shift and nuclease assays with defined flap substrate variants including the adjacent strand","pmids":["7876218"],"confidence":"High","gaps":["Structural basis of dual activity unresolved","Loading mechanism onto substrate undefined"]},{"year":1996,"claim":"Identified PCNA as a stimulatory partner and revealed FEN1 loads by tracking along the 5' ssDNA branch, connecting FEN1 to the replication machinery and explaining its directional engagement.","evidence":"Physical association assays plus nuclease stimulation assays and footprinting on adducted substrates","pmids":["8668533","8939893"],"confidence":"High","gaps":["Molecular structure of the PCNA-FEN1 interface not yet solved","Two-mode PCNA binding not yet distinguished"]},{"year":1999,"claim":"Connected FEN1 cleavage failure on repeat-derived secondary structures to repeat expansion, and assigned FEN1 a role in NHEJ via 5' flap processing, expanding its pathway repertoire beyond replication.","evidence":"In vitro cleavage with repeat-containing flaps plus yeast genetics; rad27 deletion NHEJ epistasis with flap substrates","pmids":["10635332","9990019"],"confidence":"High","gaps":["Direct in vivo evidence for expansion mechanism in mammals lacking","NHEJ partner proteins not yet identified"]},{"year":2002,"claim":"Showed WRN stimulates FEN1 catalytic efficiency independent of substrate binding and even on end-blocked substrates, distinguishing WRN-mediated from PCNA-mediated activation.","evidence":"Biochemical kinetics with multiple Okazaki intermediates and streptavidin-blocked substrates","pmids":["12356323"],"confidence":"Medium","gaps":["Structural basis of WRN stimulation unknown","Cellular context of WRN-FEN1 cooperation not yet established"]},{"year":2003,"claim":"Revealed a gap-dependent endonuclease (GEN) activity and cooperation with EndoG in apoptotic DNA fragmentation, broadening FEN1's functional scope to programmed cell death.","evidence":"RNAi and genetic epistasis in C. elegans with biochemical GEN characterization","pmids":["12840007"],"confidence":"High","gaps":["Relevance of GEN activity to mammalian apoptosis not yet shown","Substrate basis of GEN versus FEN activity unresolved"]},{"year":2004,"claim":"Provided the first structural mechanism—3' flap binding, DNA kinking, and helical clamp closure plus an intermolecular beta-sheet linking PCNA and DNA-binding regions—explaining how FEN1 achieves specificity and is coordinated by PCNA.","evidence":"X-ray crystallography of FEN1:DNA and PCNA:FEN1-peptide complexes, FRET, mutagenesis","pmids":["14718165"],"confidence":"High","gaps":["Conformation of the threaded 5' flap not captured","Two distinct PCNA binding modes not structurally reconciled"]},{"year":2004,"claim":"Reconstituted FEN1 within an ordered series of NHEJ pairwise interactions with Pol4 and Dnl4/Lif1, defining its biochemical place in end joining of incompatible ends.","evidence":"Physical interaction assays and in vitro end-joining reconstitution in S. cerevisiae","pmids":["15342630"],"confidence":"Medium","gaps":["Conservation of these interactions in mammals not demonstrated","Single-lab interaction data without structural detail"]},{"year":2006,"claim":"Mapped the GEN activity to the same clamp/ssDNA-interaction region used by FEN activity and implicated the C-terminal extension in downstream duplex contact, unifying the multiple activities mechanistically.","evidence":"Comparative kinetics of FEN/EXO/GEN with DNA-binding-deficient mutants and WRN","pmids":["16582103"],"confidence":"Medium","gaps":["Structural snapshot of GEN engagement absent","In vivo importance of GEN activity not yet tested with separation-of-function alleles"]},{"year":2005,"claim":"Placed FEN1 downstream of p53 in the stalled-fork recovery response, establishing transcriptional regulation of FEN1 by a tumor suppressor.","evidence":"Promoter reporter assays, ChIP of p53 binding, and replication-recovery rescue in p53-null cells","pmids":["16103874"],"confidence":"Medium","gaps":["Direct contribution of FEN1 enzymatic activity to fork recovery not dissected","Single-lab transcriptional data"]},{"year":2008,"claim":"Localized FEN1 to mitochondria and showed it is required for long-patch BER of oxidized abasic sites in mtDNA, extending its repair role to the mitochondrial genome.","evidence":"Subcellular fractionation, immunofluorescence, protease protection, immunodepletion, and RNAi damage-recovery assays","pmids":["18541666"],"confidence":"High","gaps":["Mitochondrial import mechanism not defined","Mitochondrial partner proteins not identified"]},{"year":2009,"claim":"Demonstrated that uncoupling of pol beta–FEN1 coordination during LP-BER allows FEN1 to ligate slipped hairpins, providing a repair-pathway mechanism for CAG repeat expansion.","evidence":"In vitro repeat-expansion reconstitution in mouse cell extracts dissecting individual enzymes including HMGB1 stimulation","pmids":["19674974"],"confidence":"Medium","gaps":["In vivo confirmation in mammalian tissue lacking","Determinants of pol beta–FEN1 uncoupling unclear"]},{"year":2010,"claim":"Showed arginine methylation at Arg192 suppresses Ser187 phosphorylation to favor PCNA binding and proper foci localization, establishing PTM-controlled timing of FEN1 activity.","evidence":"Mass spectrometry, mutagenesis, PCNA co-IP, immunofluorescence, and cell-cycle/mutation-rate readouts","pmids":["20729856"],"confidence":"High","gaps":["Identity of the responsible methyltransferase not established in this study","Phosphatase counteracting Ser187 unknown"]},{"year":2010,"claim":"Distinguished FEN1's telomere maintenance role as dependent on GEN activity and RecQ helicase interaction rather than Okazaki processing, refining which activities matter at telomeres.","evidence":"siRNA depletion with fragile/sister telomere assays and activity-specific FEN1 mutants","pmids":["20551483"],"confidence":"Medium","gaps":["Which RecQ helicase predominates not resolved","Direct telomeric substrate not defined"]},{"year":2011,"claim":"Delivered the definitive human FEN1:DNA structural mechanism—~100° bending, dual-flap capture, helical gateway threading, double-base unpairing, and two-metal-ion catalysis—explaining structure-specific, sequence-independent incision.","evidence":"X-ray crystallography of FEN1:DNA substrate and product complexes with mutagenesis and functional assays","pmids":["21496641"],"confidence":"High","gaps":["Dynamics of gateway opening not captured statically","Allosteric coupling to PCNA not fully resolved"]},{"year":2011,"claim":"Linked the FEN1-PCNA interaction directly to genome stability and cancer in vivo through a separation-of-function knock-in, demonstrating causal consequence of losing this interaction.","evidence":"FFAA knock-in mouse with BER/Okazaki biochemistry, cytogenetics, checkpoint, and tumor readouts","pmids":["21383776"],"confidence":"High","gaps":["Tissue-specific tumor spectrum not fully explained","Contribution of residual activities not isolated"]},{"year":2011,"claim":"Uncovered a crosstalk between FEN1-mediated DNA damage response and cytoskeletal signaling (p38, RhoA, actin) in response to genotoxin, broadening FEN1's cellular consequences.","evidence":"Yeast mutant screen validated by human FEN1 siRNA with signaling and cytoskeleton readouts","pmids":["21807938"],"confidence":"Medium","gaps":["Direct molecular link between FEN1 and signaling not defined","Generality beyond CDT genotoxin untested"]},{"year":2012,"claim":"Defined a sequential phosphorylation→SUMOylation→ubiquitination cascade controlling FEN1 proteasomal degradation, providing the off-switch that times FEN1 turnover with the cell cycle.","evidence":"PTM biochemistry, mutant FEN1 expression, proteasome inhibitor and cell-cycle analyses","pmids":["22749529"],"confidence":"High","gaps":["Specific E3 ligase and SUMO ligase not identified here","Spatial coordination with chromatin not defined"]},{"year":2012,"claim":"Showed FEN1 forms a more stable complex with the 9-1-1 checkpoint clamp than with PCNA, suggesting clamp-specific partitioning between repair and replication.","evidence":"Single-particle EM reconstruction (18 Å) plus molecular dynamics simulations","pmids":["22586102"],"confidence":"Medium","gaps":["High-resolution structure of the 9-1-1/FEN1 complex lacking","Functional consequence of differential stability not tested in vivo"]},{"year":2012,"claim":"Established that PARP1 is required for FEN1 recruitment to BER sites in living cells, defining the recruitment step for FEN1 at damage.","evidence":"Endogenous FEN1-YFP knock-in, live-cell laser microirradiation, and PARP1 inhibition","pmids":["22810208"],"confidence":"High","gaps":["Direct PARP1-FEN1 physical contact not demonstrated","Role of PAR chains versus protein interaction unresolved"]},{"year":2013,"claim":"Revealed at single-molecule level that FEN1 bends and locks DNA into an open-flap state and that PCNA promotes 5' ssDNA threading through the gateway, mechanistically explaining PCNA stimulation.","evidence":"Single-molecule FRET, protein-induced fluorescence enhancement, and ensemble FRET","pmids":["24234453"],"confidence":"Medium","gaps":["Kinetics relative to in vivo replication rates not established","Threading intermediate not structurally captured"]},{"year":2014,"claim":"Demonstrated via the E359K germline mutation that the FEN1-WRN interaction and GEN activity are jointly required for stalled-fork resolution and tumor suppression, separating these from flap endonuclease activity.","evidence":"Knock-in mouse, co-IP, activity assays, cytogenetics, and tumor incidence","pmids":["24608430"],"confidence":"High","gaps":["Molecular basis for E359K disrupting both interaction and GEN activity unresolved","Human germline relevance not established"]},{"year":2016,"claim":"Showed the cancer-associated L209P mutation abolishes all nuclease activities while retaining DNA binding, acting dominant-negatively to impair wild-type FEN1 and drive transformation.","evidence":"Biochemical activity/binding assays, dominant-negative cellular expression, in vitro BER, and xenograft","pmids":["27270424"],"confidence":"Medium","gaps":["Structural basis of catalytic-dead-but-binding phenotype not defined","Human tumor frequency of L209P unestablished"]},{"year":2019,"claim":"Identified FEN1 flap endonuclease activity as a synthetic-lethal vulnerability in BRCA-deficient cells via MMEJ, nominating FEN1 inhibition as a targeted therapeutic strategy.","evidence":"CRISPR screens in isogenic BRCA2-deficient lines, MMEJ reporter, activity-specific mutants, and a small-molecule inhibitor","pmids":["30686591"],"confidence":"High","gaps":["FEN1 partners in MMEJ not identified","Inhibitor specificity and in vivo efficacy not fully defined here"]},{"year":2019,"claim":"Proposed a non-canonical oncogenic role in which a FEN1/PCNA/DNMT3a complex epigenetically suppresses miR-200a-5p to derepress MET/EGFR, linking FEN1 to breast cancer proliferation.","evidence":"Co-IP, luciferase reporters, methylation-specific PCR, and siRNA knockdown","pmids":["31266372"],"confidence":"Low","gaps":["Single Co-IP without reciprocal or structural validation of the complex","Direct DNA methylation role of FEN1 not mechanistically established"]},{"year":2020,"claim":"Identified post-transcriptional and transcriptional-cofactor roles supporting FEN1's oncogenic expression—m6A-IGF2BP2 stabilization of FEN1 mRNA, PRMT1 methylation maintaining FEN1 levels, and FEN1 facilitating ERα coactivator recruitment.","evidence":"RIP and mRNA stability (IGF2BP2), co-IP and knockdown (PRMT1), and ERα co-IP/coactivator and inhibitor assays","pmids":["33224879","32861926","32193286"],"confidence":"Medium","gaps":["IGF2BP2 and PRMT1 findings rest on single-method, single-lab data","Mechanism of FEN1-ERα coactivator facilitation not structurally defined"]},{"year":null,"claim":"How FEN1's many activities and partner complexes are spatially and temporally partitioned among replication, BER, telomere maintenance, end joining, and its proposed transcriptional/epigenetic roles in vivo remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model assigning specific complexes to specific pathways in cells","Non-canonical transcriptional/epigenetic roles lack high-confidence mechanistic validation","The methyltransferase, E3, and SUMO ligase enzymes of the PTM cascade not all identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140097","term_label":"catalytic activity, acting on DNA","supporting_discovery_ids":[0,1,12,17]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[3,17,24]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[15,21]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[13]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[13,18,25]},{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[2,6,15]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[8]}],"complexes":["9-1-1 (Rad9-Hus1-Rad1) checkpoint clamp","FEN1/PCNA/DNMT3a complex"],"partners":["PCNA","WRN","RAD9-HUS1-RAD1","PARP1","POL4","DNL4/LIF1","PRMT1","IGF2BP2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P39748","full_name":"Flap endonuclease 1","aliases":["DNase IV","Flap structure-specific endonuclease 1","Maturation factor 1","MF1","hFEN-1"],"length_aa":380,"mass_kda":42.6,"function":"Structure-specific nuclease with 5'-flap endonuclease and 5'-3' exonuclease activities involved in DNA replication and repair. During DNA replication, cleaves the 5'-overhanging flap structure that is generated by displacement synthesis when DNA polymerase encounters the 5'-end of a downstream Okazaki fragment. It enters the flap from the 5'-end and then tracks to cleave the flap base, leaving a nick for ligation. Also involved in the long patch base excision repair (LP-BER) pathway, by cleaving within the apurinic/apyrimidinic (AP) site-terminated flap. Acts as a genome stabilization factor that prevents flaps from equilibrating into structures that lead to duplications and deletions. Also possesses 5'-3' exonuclease activity on nicked or gapped double-stranded DNA, and exhibits RNase H activity. Also involved in replication and repair of rDNA and in repairing mitochondrial DNA","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/P39748/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/FEN1","classification":"Common Essential","n_dependent_lines":1066,"n_total_lines":1208,"dependency_fraction":0.8824503311258278},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"RNASEH2A","stoichiometry":10.0},{"gene":"PCNA","stoichiometry":4.0},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"H1F0","stoichiometry":0.2},{"gene":"HIST2H2BE","stoichiometry":0.2},{"gene":"HMGN5","stoichiometry":0.2},{"gene":"MSH6","stoichiometry":0.2},{"gene":"PARP1","stoichiometry":0.2},{"gene":"SSRP1","stoichiometry":0.2},{"gene":"TOP1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/FEN1","total_profiled":1310},"omim":[{"mim_id":"617615","title":"TRANSMEMBRANE PROTEIN 258; TMEM258","url":"https://www.omim.org/entry/617615"},{"mim_id":"611813","title":"ELONGATION OF VERY LONG CHAIN FATTY ACIDS-LIKE 1; ELOVL1","url":"https://www.omim.org/entry/611813"},{"mim_id":"608329","title":"MYELIN REGULATORY FACTOR; MYRF","url":"https://www.omim.org/entry/608329"},{"mim_id":"606063","title":"EXONUCLEASE 1; EXO1","url":"https://www.omim.org/entry/606063"},{"mim_id":"606034","title":"RIBONUCLEASE H2, SUBUNIT A; RNASEH2A","url":"https://www.omim.org/entry/606034"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Nucleoli","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":42.9}],"url":"https://www.proteinatlas.org/search/FEN1"},"hgnc":{"alias_symbol":["FEN-1","MF1"],"prev_symbol":["RAD2"]},"alphafold":{"accession":"P39748","domains":[{"cath_id":"3.40.50.1010","chopping":"6-216","consensus_level":"medium","plddt":95.6011,"start":6,"end":216},{"cath_id":"1.10.150.20","chopping":"218-285","consensus_level":"medium","plddt":97.4662,"start":218,"end":285}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P39748","model_url":"https://alphafold.ebi.ac.uk/files/AF-P39748-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P39748-F1-predicted_aligned_error_v6.png","plddt_mean":89.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FEN1","jax_strain_url":"https://www.jax.org/strain/search?query=FEN1"},"sequence":{"accession":"P39748","fasta_url":"https://rest.uniprot.org/uniprotkb/P39748.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P39748/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P39748"}},"corpus_meta":[{"pmid":"9080773","id":"PMC_9080773","title":"The FEN-1 family of structure-specific nucleases in eukaryotic DNA replication, recombination and repair.","date":"1997","source":"BioEssays : news and reviews in molecular, cellular and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/9080773","citation_count":385,"is_preprint":false},{"pmid":"9635428","id":"PMC_9635428","title":"The forkhead/winged helix gene Mf1 is disrupted in the pleiotropic mouse mutation congenital hydrocephalus.","date":"1998","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/9635428","citation_count":312,"is_preprint":false},{"pmid":"7926735","id":"PMC_7926735","title":"Functional domains within FEN-1 and RAD2 define a family of structure-specific endonucleases: implications for nucleotide excision repair.","date":"1994","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/7926735","citation_count":278,"is_preprint":false},{"pmid":"10704385","id":"PMC_10704385","title":"Murine forkhead/winged helix genes Foxc1 (Mf1) and Foxc2 (Mfh1) are required for the early organogenesis of the kidney and urinary tract.","date":"2000","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/10704385","citation_count":276,"is_preprint":false},{"pmid":"21496641","id":"PMC_21496641","title":"Human flap endonuclease structures, DNA double-base flipping, and a unified understanding of the FEN1 superfamily.","date":"2011","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/21496641","citation_count":247,"is_preprint":false},{"pmid":"7814325","id":"PMC_7814325","title":"Characterization of a mutant strain of Saccharomyces cerevisiae with a deletion of the RAD27 gene, a structural homolog of the RAD2 nucleotide excision repair gene.","date":"1995","source":"Journal of bacteriology","url":"https://pubmed.ncbi.nlm.nih.gov/7814325","citation_count":238,"is_preprint":false},{"pmid":"14718165","id":"PMC_14718165","title":"Structural basis for FEN-1 substrate specificity and PCNA-mediated activation in DNA replication and repair.","date":"2004","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/14718165","citation_count":237,"is_preprint":false},{"pmid":"8668533","id":"PMC_8668533","title":"Processing of branched DNA intermediates by a complex of human FEN-1 and PCNA.","date":"1996","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/8668533","citation_count":187,"is_preprint":false},{"pmid":"20929870","id":"PMC_20929870","title":"Functional regulation of FEN1 nuclease and its link to cancer.","date":"2010","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/20929870","citation_count":186,"is_preprint":false},{"pmid":"30686591","id":"PMC_30686591","title":"Genetic Screens Reveal FEN1 and APEX2 as BRCA2 Synthetic Lethal Targets.","date":"2019","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/30686591","citation_count":170,"is_preprint":false},{"pmid":"18541666","id":"PMC_18541666","title":"Removal of oxidative DNA damage via FEN1-dependent long-patch base excision repair in human cell mitochondria.","date":"2008","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/18541666","citation_count":168,"is_preprint":false},{"pmid":"8674116","id":"PMC_8674116","title":"Structure of bacteriophage T4 RNase H, a 5' to 3' RNA-DNA and DNA-DNA exonuclease with sequence similarity to the RAD2 family of eukaryotic proteins.","date":"1996","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/8674116","citation_count":168,"is_preprint":false},{"pmid":"10608837","id":"PMC_10608837","title":"The RAD2 domain of human exonuclease 1 exhibits 5' to 3' exonuclease and flap structure-specific endonuclease activities.","date":"1999","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10608837","citation_count":156,"is_preprint":false},{"pmid":"8007985","id":"PMC_8007985","title":"Structural and functional conservation of the human homolog of the Schizosaccharomyces pombe rad2 gene, which is required for chromosome segregation and recovery from DNA damage.","date":"1994","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/8007985","citation_count":149,"is_preprint":false},{"pmid":"10635332","id":"PMC_10635332","title":"Inhibition of FEN-1 processing by DNA secondary structure at trinucleotide repeats.","date":"1999","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/10635332","citation_count":148,"is_preprint":false},{"pmid":"9990019","id":"PMC_9990019","title":"A role for FEN-1 in nonhomologous DNA end joining: the order of strand annealing and nucleolytic processing events.","date":"1999","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/9990019","citation_count":147,"is_preprint":false},{"pmid":"10479458","id":"PMC_10479458","title":"Roles for the winged helix transcription factors MF1 and MFH1 in cardiovascular development revealed by nonallelic noncomplementation of null alleles.","date":"1999","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/10479458","citation_count":145,"is_preprint":false},{"pmid":"10395790","id":"PMC_10395790","title":"The forkhead/winged-helix gene, Mf1, is necessary for the normal development of the cornea and formation of the anterior chamber in the mouse eye.","date":"1999","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/10395790","citation_count":142,"is_preprint":false},{"pmid":"10899134","id":"PMC_10899134","title":"Two modes of FEN1 binding to PCNA regulated by DNA.","date":"2000","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/10899134","citation_count":134,"is_preprint":false},{"pmid":"8247134","id":"PMC_8247134","title":"Yeast excision repair gene RAD2 encodes a single-stranded DNA endonuclease.","date":"1993","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/8247134","citation_count":130,"is_preprint":false},{"pmid":"33224879","id":"PMC_33224879","title":"IGF2BP2 Promotes Liver Cancer Growth Through an m6A-FEN1-Dependent Mechanism.","date":"2020","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/33224879","citation_count":128,"is_preprint":false},{"pmid":"15954100","id":"PMC_15954100","title":"Multiple but dissectible functions of FEN-1 nucleases in nucleic acid processing, genome stability and diseases.","date":"2005","source":"BioEssays : news and reviews in molecular, cellular and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/15954100","citation_count":123,"is_preprint":false},{"pmid":"20729856","id":"PMC_20729856","title":"Methylation of FEN1 suppresses nearby phosphorylation and facilitates PCNA binding.","date":"2010","source":"Nature chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/20729856","citation_count":115,"is_preprint":false},{"pmid":"12840007","id":"PMC_12840007","title":"CRN-1, a Caenorhabditis elegans FEN-1 homologue, cooperates with CPS-6/EndoG to promote apoptotic DNA degradation.","date":"2003","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/12840007","citation_count":105,"is_preprint":false},{"pmid":"19674974","id":"PMC_19674974","title":"Coordination between polymerase beta and FEN1 can modulate CAG repeat expansion.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19674974","citation_count":101,"is_preprint":false},{"pmid":"9685493","id":"PMC_9685493","title":"Hex1: a new human Rad2 nuclease family member with homology to yeast exonuclease 1.","date":"1998","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/9685493","citation_count":100,"is_preprint":false},{"pmid":"3011752","id":"PMC_3011752","title":"Nucleotide sequence, transcript mapping, and regulation of the RAD2 gene of Saccharomyces cerevisiae.","date":"1986","source":"Journal of bacteriology","url":"https://pubmed.ncbi.nlm.nih.gov/3011752","citation_count":91,"is_preprint":false},{"pmid":"28371273","id":"PMC_28371273","title":"FEN1 promotes tumor progression and confers cisplatin resistance in non-small-cell lung cancer.","date":"2017","source":"Molecular oncology","url":"https://pubmed.ncbi.nlm.nih.gov/28371273","citation_count":89,"is_preprint":false},{"pmid":"22749529","id":"PMC_22749529","title":"Sequential posttranslational modifications program FEN1 degradation during cell-cycle progression.","date":"2012","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/22749529","citation_count":87,"is_preprint":false},{"pmid":"10072431","id":"PMC_10072431","title":"Pleiotropic skeletal and ocular phenotypes of the mouse mutation congenital hydrocephalus (ch/Mf1) arise from a winged helix/forkhead transcriptionfactor gene.","date":"1999","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10072431","citation_count":85,"is_preprint":false},{"pmid":"7876218","id":"PMC_7876218","title":"DNA structural elements required for FEN-1 binding.","date":"1995","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7876218","citation_count":84,"is_preprint":false},{"pmid":"31471584","id":"PMC_31471584","title":"MicroRNA-140 impedes DNA repair by targeting FEN1 and enhances chemotherapeutic response in breast cancer.","date":"2019","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/31471584","citation_count":83,"is_preprint":false},{"pmid":"32719125","id":"PMC_32719125","title":"FEN1 endonuclease as a therapeutic target for human cancers with defects in homologous recombination.","date":"2020","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/32719125","citation_count":76,"is_preprint":false},{"pmid":"12110180","id":"PMC_12110180","title":"Requirement of yeast RAD2, a homolog of human XPG gene, for efficient RNA polymerase II transcription. implications for Cockayne syndrome.","date":"2002","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/12110180","citation_count":75,"is_preprint":false},{"pmid":"19618370","id":"PMC_19618370","title":"Functional FEN1 polymorphisms are associated with DNA damage levels and lung cancer risk.","date":"2009","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/19618370","citation_count":71,"is_preprint":false},{"pmid":"8196602","id":"PMC_8196602","title":"Yeast nucleotide excision repair proteins Rad2 and Rad4 interact with RNA polymerase II basal transcription factor b (TFIIH).","date":"1994","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/8196602","citation_count":65,"is_preprint":false},{"pmid":"14562054","id":"PMC_14562054","title":"Increased expression and no mutation of the Flap endonuclease (FEN1) gene in human lung cancer.","date":"2003","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/14562054","citation_count":65,"is_preprint":false},{"pmid":"20551483","id":"PMC_20551483","title":"FEN1 ensures telomere stability by facilitating replication fork re-initiation.","date":"2010","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20551483","citation_count":64,"is_preprint":false},{"pmid":"7774922","id":"PMC_7774922","title":"Sequence of human FEN-1, a structure-specific endonuclease, and chromosomal localization of the gene (FEN1) in mouse and human.","date":"1995","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/7774922","citation_count":63,"is_preprint":false},{"pmid":"12917330","id":"PMC_12917330","title":"Nuclease-deficient FEN-1 blocks Rad51/BRCA1-mediated repair and causes trinucleotide repeat instability.","date":"2003","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12917330","citation_count":62,"is_preprint":false},{"pmid":"12356323","id":"PMC_12356323","title":"Biochemical characterization of the WRN-FEN-1 functional interaction.","date":"2002","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12356323","citation_count":62,"is_preprint":false},{"pmid":"16055708","id":"PMC_16055708","title":"Fen-1 facilitates homologous recombination by removing divergent sequences at DNA break ends.","date":"2005","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16055708","citation_count":61,"is_preprint":false},{"pmid":"25885449","id":"PMC_25885449","title":"YY1 suppresses FEN1 over-expression and drug resistance in breast cancer.","date":"2015","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/25885449","citation_count":57,"is_preprint":false},{"pmid":"10474162","id":"PMC_10474162","title":"Expression of the Mf1 gene in developing mouse hearts: implication in the development of human congenital heart defects.","date":"1999","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/10474162","citation_count":55,"is_preprint":false},{"pmid":"29541412","id":"PMC_29541412","title":"Curcumin increases breast cancer cell sensitivity to cisplatin by decreasing FEN1 expression.","date":"2018","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/29541412","citation_count":55,"is_preprint":false},{"pmid":"12136109","id":"PMC_12136109","title":"Vertebrate cells lacking FEN-1 endonuclease are viable but hypersensitive to methylating agents and H2O2.","date":"2002","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/12136109","citation_count":53,"is_preprint":false},{"pmid":"1561835","id":"PMC_1561835","title":"Sequence of a 10.7 kb segment of yeast chromosome XI identifies the APN1 and the BAF1 loci and reveals one tRNA gene and several new open reading frames including homologs to RAD2 and kinases.","date":"1992","source":"Yeast (Chichester, England)","url":"https://pubmed.ncbi.nlm.nih.gov/1561835","citation_count":51,"is_preprint":false},{"pmid":"8855246","id":"PMC_8855246","title":"Transcription factor TFIIH and DNA endonuclease Rad2 constitute yeast nucleotide excision repair factor 3: implications for nucleotide excision repair and Cockayne syndrome.","date":"1996","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/8855246","citation_count":49,"is_preprint":false},{"pmid":"7989298","id":"PMC_7989298","title":"A conserved 5' to 3' exonuclease activity in the yeast and human nucleotide excision repair proteins RAD2 and XPG.","date":"1994","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7989298","citation_count":48,"is_preprint":false},{"pmid":"22586102","id":"PMC_22586102","title":"Repair complexes of FEN1 endonuclease, DNA, and Rad9-Hus1-Rad1 are distinguished from their PCNA counterparts by functionally important stability.","date":"2012","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/22586102","citation_count":48,"is_preprint":false},{"pmid":"21383776","id":"PMC_21383776","title":"Fen1 mutations that specifically disrupt its interaction with PCNA cause aneuploidy-associated cancer.","date":"2011","source":"Cell research","url":"https://pubmed.ncbi.nlm.nih.gov/21383776","citation_count":48,"is_preprint":false},{"pmid":"8530429","id":"PMC_8530429","title":"Structure-specific nuclease activity in yeast nucleotide excision repair protein Rad2.","date":"1995","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/8530429","citation_count":47,"is_preprint":false},{"pmid":"6366519","id":"PMC_6366519","title":"Saccharomyces cerevisiae RAD2 gene: isolation, subcloning, and partial characterization.","date":"1984","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/6366519","citation_count":45,"is_preprint":false},{"pmid":"2695743","id":"PMC_2695743","title":"Regulation of the RAD2 gene of Saccharomyces cerevisiae.","date":"1989","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/2695743","citation_count":44,"is_preprint":false},{"pmid":"8939893","id":"PMC_8939893","title":"Mechanism of tracking and cleavage of adduct-damaged DNA substrates by the mammalian 5'- to 3'-exonuclease/endonuclease RAD2 homologue 1 or flap endonuclease 1.","date":"1996","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/8939893","citation_count":44,"is_preprint":false},{"pmid":"11948189","id":"PMC_11948189","title":"DNA ligase I competes with FEN1 to expand repetitive DNA sequences in vitro.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11948189","citation_count":44,"is_preprint":false},{"pmid":"35883563","id":"PMC_35883563","title":"Small-Molecule Inhibitors Targeting FEN1 for Cancer Therapy.","date":"2022","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/35883563","citation_count":43,"is_preprint":false},{"pmid":"11578611","id":"PMC_11578611","title":"Minimal ischaemic neuronal damage and HSP70 expression in MF1 strain mice following bilateral common carotid artery occlusion.","date":"2001","source":"Brain research","url":"https://pubmed.ncbi.nlm.nih.gov/11578611","citation_count":43,"is_preprint":false},{"pmid":"31266372","id":"PMC_31266372","title":"FEN1 mediates miR-200a methylation and promotes breast cancer cell growth via MET and EGFR signaling.","date":"2019","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/31266372","citation_count":41,"is_preprint":false},{"pmid":"3000874","id":"PMC_3000874","title":"The RAD2 gene of Saccharomyces cerevisiae: nucleotide sequence and transcript mapping.","date":"1985","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/3000874","citation_count":40,"is_preprint":false},{"pmid":"15342630","id":"PMC_15342630","title":"Processing and joining of DNA ends coordinated by interactions among Dnl4/Lif1, Pol4, and FEN-1.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15342630","citation_count":40,"is_preprint":false},{"pmid":"16582103","id":"PMC_16582103","title":"The DNA-protein interaction modes of FEN-1 with gap substrates and their implication in preventing duplication mutations.","date":"2006","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/16582103","citation_count":39,"is_preprint":false},{"pmid":"33847477","id":"PMC_33847477","title":"Dual-Mode FEN1 Activity Detection Based on Nt.BstNBI-Induced Tandem Signal Amplification.","date":"2021","source":"Analytical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/33847477","citation_count":38,"is_preprint":false},{"pmid":"9545561","id":"PMC_9545561","title":"Expression of the mouse Fkh1/Mf1 and Mfh1 genes in late gestation embryos is restricted to mesoderm derivatives.","date":"1998","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/9545561","citation_count":38,"is_preprint":false},{"pmid":"34342424","id":"PMC_34342424","title":"Precision Spherical Nucleic Acids Enable Sensitive FEN1 Imaging and Controllable Drug Delivery for Cancer-Specific Therapy.","date":"2021","source":"Analytical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/34342424","citation_count":38,"is_preprint":false},{"pmid":"27270424","id":"PMC_27270424","title":"The FEN1 L209P mutation interferes with long-patch base excision repair and induces cellular transformation.","date":"2016","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/27270424","citation_count":37,"is_preprint":false},{"pmid":"37185662","id":"PMC_37185662","title":"Down-regulation of DNA key protein-FEN1 inhibits OSCC growth by affecting immunosuppressive phenotypes via IFN-γ/JAK/STAT-1.","date":"2023","source":"International journal of oral science","url":"https://pubmed.ncbi.nlm.nih.gov/37185662","citation_count":35,"is_preprint":false},{"pmid":"24234453","id":"PMC_24234453","title":"Single-molecule characterization of Fen1 and Fen1/PCNA complexes acting on flap substrates.","date":"2013","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/24234453","citation_count":33,"is_preprint":false},{"pmid":"32861926","id":"PMC_32861926","title":"PRMT1 is critical to FEN1 expression and drug resistance in lung cancer cells.","date":"2020","source":"DNA repair","url":"https://pubmed.ncbi.nlm.nih.gov/32861926","citation_count":33,"is_preprint":false},{"pmid":"14599892","id":"PMC_14599892","title":"Role of the Mf1-1 pheromone precursor gene of the filamentous ascomycete Cryphonectria parasitica.","date":"2003","source":"Fungal genetics and biology : FG & B","url":"https://pubmed.ncbi.nlm.nih.gov/14599892","citation_count":33,"is_preprint":false},{"pmid":"24298055","id":"PMC_24298055","title":"Mediator links transcription and DNA repair by facilitating Rad2/XPG recruitment.","date":"2013","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/24298055","citation_count":32,"is_preprint":false},{"pmid":"31670906","id":"PMC_31670906","title":"FEN1 inhibitor increases sensitivity of radiotherapy in cervical cancer cells.","date":"2019","source":"Cancer medicine","url":"https://pubmed.ncbi.nlm.nih.gov/31670906","citation_count":32,"is_preprint":false},{"pmid":"16103874","id":"PMC_16103874","title":"Fen1 is induced p53 dependently and involved in the recovery from UV-light-induced replication inhibition.","date":"2005","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/16103874","citation_count":32,"is_preprint":false},{"pmid":"22373916","id":"PMC_22373916","title":"Structural and functional characterization of interactions involving the Tfb1 subunit of TFIIH and the NER factor Rad2.","date":"2012","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/22373916","citation_count":30,"is_preprint":false},{"pmid":"6392021","id":"PMC_6392021","title":"Isolation and characterization of the RAD2 gene of Saccharomyces cerevisiae.","date":"1984","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/6392021","citation_count":30,"is_preprint":false},{"pmid":"12602891","id":"PMC_12602891","title":"OsSEND-1: a new RAD2 nuclease family member in higher plants.","date":"2003","source":"Plant molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12602891","citation_count":30,"is_preprint":false},{"pmid":"22810208","id":"PMC_22810208","title":"Kinetics of endogenous mouse FEN1 in base excision repair.","date":"2012","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/22810208","citation_count":30,"is_preprint":false},{"pmid":"15915339","id":"PMC_15915339","title":"Genetic and physical interactions between Schizosaccharomyces pombe Mcl1 and Rad2, Dna2 and DNA polymerase alpha: evidence for a multifunctional role of Mcl1 in DNA replication and repair.","date":"2005","source":"Current genetics","url":"https://pubmed.ncbi.nlm.nih.gov/15915339","citation_count":29,"is_preprint":false},{"pmid":"7491120","id":"PMC_7491120","title":"The yeast RAD2, but not RAD1, gene is involved in the transcription-coupled repair of thymine glycols.","date":"1995","source":"Mutation research","url":"https://pubmed.ncbi.nlm.nih.gov/7491120","citation_count":29,"is_preprint":false},{"pmid":"10211123","id":"PMC_10211123","title":"Fen1 expression: a novel marker for cell proliferation.","date":"1998","source":"The Journal of pathology","url":"https://pubmed.ncbi.nlm.nih.gov/10211123","citation_count":27,"is_preprint":false},{"pmid":"9079876","id":"PMC_9079876","title":"Characterization of a novel DNA damage-inducible gene of Saccharomyces cerevisiae, DIN7, which is a structural homolog of the RAD2 and RAD27 DNA repair genes.","date":"1997","source":"Molecular & general genetics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/9079876","citation_count":27,"is_preprint":false},{"pmid":"32193286","id":"PMC_32193286","title":"Endonuclease FEN1 Coregulates ERα Activity and Provides a Novel Drug Interface in Tamoxifen-Resistant Breast Cancer.","date":"2020","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/32193286","citation_count":27,"is_preprint":false},{"pmid":"1557031","id":"PMC_1557031","title":"Regulation of the yeast RAD2 gene: DNA damage-dependent induction correlates with protein binding to regulatory sequences and their deletion influences survival.","date":"1992","source":"Molecular & general genetics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/1557031","citation_count":26,"is_preprint":false},{"pmid":"12893088","id":"PMC_12893088","title":"Complementary functions of the Saccharomyces cerevisiae Rad2 family nucleases in Okazaki fragment maturation, mutation avoidance, and chromosome stability.","date":"2003","source":"DNA repair","url":"https://pubmed.ncbi.nlm.nih.gov/12893088","citation_count":25,"is_preprint":false},{"pmid":"36641157","id":"PMC_36641157","title":"Programmable CRISPR-Cas12a and self-recruiting crRNA assisted dual biosensing platform for simultaneous detection of lung cancer biomarkers hOGG1 and FEN1.","date":"2022","source":"Analytica chimica acta","url":"https://pubmed.ncbi.nlm.nih.gov/36641157","citation_count":25,"is_preprint":false},{"pmid":"9685478","id":"PMC_9685478","title":"Characterization of Schizosaccharomyces pombe Rad2 protein, a FEN-1 homolog.","date":"1998","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/9685478","citation_count":24,"is_preprint":false},{"pmid":"21807938","id":"PMC_21807938","title":"Bacterial genotoxin triggers FEN1-dependent RhoA activation, cytoskeleton remodeling and cell survival.","date":"2011","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/21807938","citation_count":23,"is_preprint":false},{"pmid":"24608430","id":"PMC_24608430","title":"The FEN1 E359K germline mutation disrupts the FEN1-WRN interaction and FEN1 GEN activity, causing aneuploidy-associated cancers.","date":"2014","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/24608430","citation_count":22,"is_preprint":false},{"pmid":"25120270","id":"PMC_25120270","title":"Crystal structure of the catalytic core of Rad2: insights into the mechanism of substrate binding.","date":"2014","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/25120270","citation_count":22,"is_preprint":false},{"pmid":"33919707","id":"PMC_33919707","title":"FEN1 Blockade for Platinum Chemo-Sensitization and Synthetic Lethality in Epithelial Ovarian Cancers.","date":"2021","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/33919707","citation_count":21,"is_preprint":false},{"pmid":"24440783","id":"PMC_24440783","title":"Association of functional FEN1 genetic variants and haplotypes and breast cancer risk.","date":"2014","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/24440783","citation_count":20,"is_preprint":false},{"pmid":"27010693","id":"PMC_27010693","title":"Association between Single-Nucleotide Polymorphisms of the hOGG1,NEIL1,APEX1, FEN1,LIG1, and LIG3 Genes and Alzheimer's Disease Risk.","date":"2016","source":"Neuropsychobiology","url":"https://pubmed.ncbi.nlm.nih.gov/27010693","citation_count":20,"is_preprint":false},{"pmid":"28416706","id":"PMC_28416706","title":"The GAN Exonuclease or the Flap Endonuclease Fen1 and RNase HII Are Necessary for Viability of Thermococcus kodakarensis.","date":"2017","source":"Journal of bacteriology","url":"https://pubmed.ncbi.nlm.nih.gov/28416706","citation_count":20,"is_preprint":false},{"pmid":"38360994","id":"PMC_38360994","title":"PARG-deficient tumor cells have an increased dependence on EXO1/FEN1-mediated DNA repair.","date":"2024","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/38360994","citation_count":19,"is_preprint":false},{"pmid":"3332971","id":"PMC_3332971","title":"Overexpression of the RAD2 gene of S. cerevisiae: identification and preliminary characterization of Rad2 protein.","date":"1987","source":"Yeast (Chichester, England)","url":"https://pubmed.ncbi.nlm.nih.gov/3332971","citation_count":19,"is_preprint":false},{"pmid":"2663184","id":"PMC_2663184","title":"The Saccharomyces cerevisiae RAD2 gene complements a Schizosaccharomyces pombe repair mutation.","date":"1989","source":"Current genetics","url":"https://pubmed.ncbi.nlm.nih.gov/2663184","citation_count":18,"is_preprint":false},{"pmid":"35246224","id":"PMC_35246224","title":"miR-4324 inhibits ovarian cancer progression by targeting FEN1.","date":"2022","source":"Journal of ovarian research","url":"https://pubmed.ncbi.nlm.nih.gov/35246224","citation_count":18,"is_preprint":false},{"pmid":"37354713","id":"PMC_37354713","title":"FEN1-aided recombinase polymerase amplification (FARPA) for one-pot and multiplex detection of nucleic acids with an ultra-high specificity and sensitivity.","date":"2023","source":"Biosensors & bioelectronics","url":"https://pubmed.ncbi.nlm.nih.gov/37354713","citation_count":18,"is_preprint":false},{"pmid":"15576351","id":"PMC_15576351","title":"DmGEN, a novel RAD2 family endo-exonuclease from Drosophila melanogaster.","date":"2004","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/15576351","citation_count":18,"is_preprint":false},{"pmid":"11800554","id":"PMC_11800554","title":"Role of the DNA repair nucleases Rad13, Rad2 and Uve1 of Schizosaccharomyces pombe in mismatch correction.","date":"2001","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11800554","citation_count":17,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":44905,"output_tokens":7603,"usd":0.12438,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":17234,"output_tokens":7313,"usd":0.134497,"stage2_stop_reason":"end_turn"},"total_usd":0.258877,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1994,\n      \"finding\": \"FEN-1 is a structure-specific endonuclease that cleaves DNA flap structures (5' flap and pseudo Y-structures); the murine FEN-1 gene was cloned and shown to be homologous to S. cerevisiae YKL510 (RAD27) and RAD2. YKL510 and a truncated RAD2 protein were also demonstrated to be structure-specific endonucleases with similar substrate specificity.\",\n      \"method\": \"Gene cloning, in vitro nuclease assays with branched DNA substrates\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro enzymatic characterization with defined substrates, replicated across multiple homologs\",\n      \"pmids\": [\"7926735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"FEN-1 binding and cleavage of flap DNA structures requires the adjacent (Fadj) strand that provides a double-stranded template near the elbow of the flap; absence or recession of this strand dramatically reduces binding efficiency. FEN-1 possesses both 5'-flap endonuclease and double-stranded DNA 5'-exonuclease activity within the same 42 kDa enzyme.\",\n      \"method\": \"Mobility shift assay, in vitro nuclease assays with defined DNA substrates\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro binding and cleavage assays with multiple substrate variants, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"7876218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Human PCNA physically associates with human FEN-1 and stimulates its endonucleolytic activity at branched DNA (flap) structures and its exonucleolytic activity at nick and gap structures. PCNA loads onto substrates at double-stranded DNA ends, while FEN-1 loads by tracking along the single-stranded DNA branch from its free 5' terminus.\",\n      \"method\": \"Physical association (co-purification/interaction assays), in vitro nuclease stimulation assays with defined DNA substrates\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — physical interaction plus functional stimulation demonstrated in vitro, replicated and extended by subsequent structural studies\",\n      \"pmids\": [\"8668533\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"FEN-1 (RAD2 homologue 1) tracks along the single-stranded 5' tail of a flap substrate from its 5' end to the cleavage point, protecting a ~25 nucleotide region adjacent to the cleavage site, and can cleave past adducts (CDDP) located within or beyond the protected region, but is inhibited by an adduct immediately adjacent to the cleavage point.\",\n      \"method\": \"Micrococcal nuclease footprinting, in vitro cleavage assays with site-specifically adducted DNA substrates\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct mechanistic footprinting and cleavage assays, single lab\",\n      \"pmids\": [\"8939893\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"DNA secondary structures formed at trinucleotide repeat sequences (CAG, CGG, CTG) inhibit FEN-1 cleavage in a length-dependent manner by concealing the 5' end of the flap required for FEN-1 binding and cleavage, providing a mechanism for repeat expansion.\",\n      \"method\": \"In vitro FEN-1 cleavage assays with repeat-containing flap substrates; genetic studies in yeast lacking FEN-1\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biochemical reconstitution with defined substrates plus genetic validation, single lab with two orthogonal approaches\",\n      \"pmids\": [\"10635332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Deletion of RAD27 (yeast FEN-1) leads to a 4.4-fold reduction specifically in NHEJ events predicted to proceed via 5' flap intermediates, establishing a role for FEN-1 in non-homologous DNA end joining through processing of 5' flap structures that arise after end alignment.\",\n      \"method\": \"Genetic epistasis in S. cerevisiae; NHEJ assay with specific substrates in rad27 deletion strains\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with defined substrate specificity, single lab\",\n      \"pmids\": [\"9990019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"FEN1 interacts with PCNA through two distinct modes: in solution (without DNA), FEN1 binds primarily through the PCNA interdomain connector loop (IDCL); when PCNA encircles DNA, the C-terminal domain of PCNA (not the IDCL) is critical for FEN1 binding and stimulation of activity. An FF→GA mutation in FEN1's PCNA-interaction domain abolishes both modes and causes replication and repair defects in vivo.\",\n      \"method\": \"Yeast genetics with PCNA mutants (pcna-79, pcna-90), DNA-bead retention assay, FEN1 mutagenesis, in vivo complementation\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple PCNA and FEN1 mutants tested with biochemical and genetic assays, single lab with orthogonal methods\",\n      \"pmids\": [\"10899134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"WRN protein physically interacts with FEN-1 and stimulates its cleavage activity by enhancing catalytic efficiency rather than DNA substrate binding. WRN stimulates FEN-1 on multiple Okazaki fragment processing intermediates including flaps with terminal monoribonucleotides, long 5' ssDNA tracts, and pseudo-Y structures, and does so even when a free upstream end is blocked (unlike PCNA-mediated stimulation).\",\n      \"method\": \"Biochemical kinetics of FEN-1 cleavage in the presence/absence of WRN, substrate binding assays, streptavidin-blocked substrate experiments\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinetic characterization with multiple substrates and mechanistic controls, single lab\",\n      \"pmids\": [\"12356323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"C. elegans CRN-1 (FEN-1 homolog) cooperates with CPS-6/EndoG to promote apoptotic DNA degradation. CRN-1 utilizes its 5'-3' exonuclease activity and a newly identified gap-dependent endonuclease (GEN) activity together with CPS-6 endonuclease activity for stepwise DNA fragmentation during apoptosis.\",\n      \"method\": \"RNAi knockdown in C. elegans, genetic interaction with cps-6 mutant, biochemical characterization of GEN activity\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic epistasis plus biochemical identification of novel GEN activity, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"12840007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Crystal structures of FEN-1:DNA and PCNA:FEN-1-peptide complexes reveal that FEN-1 binds the unpaired 3' DNA end (3' flap), opens and kinks DNA, and promotes conformational closing of a flexible helical clamp to facilitate 5' cleavage specificity. Ordering of unstructured C-terminal regions in FEN-1 and PCNA creates an intermolecular beta-sheet interface directly linking PCNA and DNA binding regions of FEN-1. FRET and mutagenesis support a kinked DNA pivot point for coordinated handoffs.\",\n      \"method\": \"X-ray crystallography, FRET, site-directed mutagenesis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures plus FRET and mutagenesis in a single rigorous study, multiple orthogonal methods\",\n      \"pmids\": [\"14718165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"In S. cerevisiae NHEJ, FEN-1 (Rad27) physically and functionally interacts with Pol4 and Dnl4/Lif1, and together these proteins coordinately process and join DNA molecules with incompatible 5' ends, establishing a series of pairwise interactions that complete DSB repair by NHEJ.\",\n      \"method\": \"Physical interaction assays (co-immunoprecipitation/pulldown), in vitro end-joining reconstitution with defined substrates\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — physical and functional interaction demonstrated in vitro with multiple proteins, single lab\",\n      \"pmids\": [\"15342630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"FEN-1-deficient chicken DT40 cells show decreased efficiency of immunoglobulin gene conversion (HR between divergent sequences) but are proficient in sister chromatid recombination, indicating FEN-1 eliminates heterologous sequences at DNA break sites to facilitate HR. This was confirmed by I-SceI-induced DSB experiments with divergent donor/recipient substrates.\",\n      \"method\": \"Gene knockout in chicken DT40 cells, I-SceI-induced recombination assays, gene conversion frequency measurement\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with specific phenotypic readouts and mechanistic substrate manipulation, single lab\",\n      \"pmids\": [\"16055708\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"FEN-1's gap endonuclease (GEN) activity uses the same clamp region that FEN activity uses to interact with single-stranded DNA substrates. The C-terminal extension of human FEN-1 likely interacts with the downstream duplex in all substrate types, and GEN activity in complex with WRN can cleave hairpin and internal loop substrates, suggesting a role in preventing repeat expansions.\",\n      \"method\": \"Kinetic analysis of FEN, EXO, and GEN activities; DNA-binding deficient FEN1 mutants; biochemical assays with WRN\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — comparative kinetics with multiple mutants and substrates, single lab with two orthogonal methods\",\n      \"pmids\": [\"16582103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"FEN1 is present in human mitochondria (confirmed by protease protection of mitochondria, immunofluorescence, and subcellular fractionation) and participates in long-patch base excision repair (LP-BER) of oxidized abasic sites (2-deoxyribonolactone) in mitochondrial DNA. Immunodepletion of FEN1 from mitochondrial extracts strongly diminishes LP-BER activity.\",\n      \"method\": \"Subcellular fractionation, immunofluorescence, protease protection assay, immunodepletion of mitochondrial extracts, RNAi knockdown with damage recovery assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal localization and functional methods, immunodepletion directly linking FEN1 to LP-BER activity in mitochondria\",\n      \"pmids\": [\"18541666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"FEN1 promotes CAG repeat expansion during long-patch BER by facilitating ligation of hairpins formed by strand slippage, resulting from uncoupling of normal pol beta–FEN1 coordination during multinucleotide gap-filling synthesis. HMGB1 promotes expansion by stimulating APE1 and FEN1.\",\n      \"method\": \"In vitro reconstitution of repeat expansion using mouse cell extracts; biochemical assays dissecting individual enzyme contributions\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biochemical reconstitution in cell extracts with defined substrates, single lab\",\n      \"pmids\": [\"19674974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"FEN1 is methylated at arginine residues (primarily Arg192) by an arginine methyltransferase; this methylation suppresses phosphorylation at Ser187. The methylated form (but not the phosphorylated form) strongly interacts with PCNA, ensuring proper timing of FEN1 activity. Mutations disrupting arginine methylation cause unscheduled phosphorylation, failure to localize to DNA replication/repair foci, defects in Okazaki fragment maturation, cell cycle delay, impaired DNA repair, and elevated genome-wide mutation rates.\",\n      \"method\": \"Mass spectrometry identification of methylation sites, site-directed mutagenesis, co-immunoprecipitation with PCNA, immunofluorescence localization, cell cycle analysis\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — MS identification plus mutagenesis plus interaction studies plus localization and functional readouts, multiple orthogonal methods\",\n      \"pmids\": [\"20729856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"FEN1 is required for efficient replication fork re-initiation at telomeres. FEN1 gap endonuclease activity (not Okazaki fragment processing activity) and the FEN1 interaction with RecQ helicases are vital for telomere stability, as FEN1 depletion causes fragile telomere expression and sister telomere loss.\",\n      \"method\": \"FEN1 siRNA depletion, fragile telomere and sister telomere loss assays, functional dissection using FEN1 activity mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with mechanistic dissection using activity-specific mutants, single lab\",\n      \"pmids\": [\"20551483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structures and functional analyses of human FEN1:DNA complexes reveal structure-specific, sequence-independent recognition: FEN1 binds nicked dsDNA bent ~100° with unpaired 3' and 5' flaps. A helical cap over a gateway formed by two helices enforces ssDNA threading and specificity for free 5' ends. Double-base unpairing flanking the scissile phosphate and the two-metal-ion active site control precise flap incision.\",\n      \"method\": \"X-ray crystallography of FEN1:DNA product and substrate complexes, mutagenesis, functional assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple crystal structures plus mutagenesis, comprehensive mechanistic study in single rigorous publication\",\n      \"pmids\": [\"21496641\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"A FEN1 point mutation (F343A/F344A, FFAA) that specifically abolishes the FEN1/PCNA interaction causes defects in RNA primer removal and long-patch BER, resulting in DNA breaks, G2/M checkpoint activation (via Chk1), near-tetraploid aneuploidy, elevated cellular transformation frequency, and cancer in knock-in mice.\",\n      \"method\": \"Knock-in mouse model, biochemical assays for BER and Okazaki fragment processing, cytogenetic analysis, transformation assays\",\n      \"journal\": \"Cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knock-in mouse model with multiple orthogonal readouts directly linking a specific protein-protein interaction to mechanistic consequences\",\n      \"pmids\": [\"21383776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"FEN1 undergoes sequential post-translational modifications controlling its proteasomal degradation: phosphorylation stimulates SUMOylation, which in turn stimulates ubiquitination and proteasomal degradation. Blocking any step in this cascade suppresses FEN1 degradation and causes accumulation of Cyclin B, G1/G2M phase delays, and polyploidy.\",\n      \"method\": \"Biochemical characterization of PTMs, mutant FEN1 expression, cell cycle analysis, proteasome inhibitor experiments\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — sequential PTM cascade dissected with multiple mutants and inhibitors, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"22749529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"FEN1 forms a complex with the checkpoint clamp Rad9-Hus1-Rad1 (9-1-1) in addition to PCNA. The 9-1-1/FEN1/DNA assembly has greater stability than the PCNA/FEN1/DNA complex, as determined by 3D electron microscopy reconstruction at 18-Å resolution combined with molecular dynamics simulations, consistent with distinct roles in DNA repair versus replication.\",\n      \"method\": \"Single-particle electron microscopy, molecular dynamics simulations, computational modeling\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — EM structure of ternary complex plus MD simulations, single study with structural and computational methods\",\n      \"pmids\": [\"22586102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Endogenous FEN1-YFP rapidly accumulates at local laser-induced DNA damage sites in living cells. PARP1 inhibition disrupts FEN1 accumulation at DNA repair intermediates, establishing that PARP1 is required for FEN1 recruitment to BER sites.\",\n      \"method\": \"Fluorescent knock-in mouse model (FEN1-YFP), live-cell multi-photon fluorescence microscopy, PARP1 inhibitor treatment\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — endogenous tagged protein in living cells/tissues, direct PARP1 dependency demonstrated, multiple orthogonal methods\",\n      \"pmids\": [\"22810208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The FEN1 E359K germline mutation abolishes the FEN1-WRN interaction (critical for resolving stalled replication forks) and eliminates FEN1 gap-dependent endonuclease (GEN) activity while leaving flap endonuclease activity intact. E359K mouse embryonic fibroblasts are hypersensitive to DNA crosslinking agents, show fragile telomeres and increased chromosomal anomalies, and E359K homozygous mice develop cancer at high frequency.\",\n      \"method\": \"Knock-in mouse model, co-immunoprecipitation, in vitro biochemical activity assays, cytogenetic analysis, tumor incidence measurement\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knock-in mouse model with biochemical dissection of specific interaction and activity, multiple orthogonal methods\",\n      \"pmids\": [\"24608430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Single-molecule FRET and protein-induced fluorescence enhancement studies reveal that upon FEN1 binding, a flap DNA substrate is bent and locked into an open flap conformation. PCNA enhances FEN1 recognition by further promoting the open flap conformation, likely by facilitating threading of the 5' ssDNA flap through the helical gateway.\",\n      \"method\": \"Single-molecule FRET, protein-induced fluorescence enhancement, ensemble FRET\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule biophysics with multiple methods, single lab\",\n      \"pmids\": [\"24234453\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The cancer-associated FEN1 L209P mutation abolishes FEN, EXO, and GEN nuclease activities but retains DNA-binding affinity, acting in a dominant-negative manner to impair wild-type FEN1 function and long-patch BER in vitro and in vivo, leading to genomic instability and cellular transformation.\",\n      \"method\": \"Biochemical activity assays, DNA binding assays, dominant-negative expression in cells, in vitro BER assays, mouse xenograft\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical characterization plus cellular and in vivo validation, single lab with multiple methods\",\n      \"pmids\": [\"27270424\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FEN1 participates in microhomology-mediated end-joining (MMEJ); BRCA2-deficient cells require specifically the 5' flap endonuclease activity (not the 5'-3' exonuclease activity) of FEN1, and chemical inhibition of FEN1 selectively targets BRCA-deficient cells.\",\n      \"method\": \"CRISPR-based genetic screens in isogenic BRCA2-deficient cell lines, MMEJ reporter assay, FEN1 activity-specific mutants, small-molecule FEN1 inhibitor\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide screens validated with MMEJ reporter and activity-specific dissection, multiple orthogonal approaches\",\n      \"pmids\": [\"30686591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FEN1 promotes breast cancer cell proliferation via formation of a FEN1/PCNA/DNMT3a complex that suppresses miR-200a-5p expression through DNA methylation, thereby allowing expression of miR-200a target genes MET and EGFR.\",\n      \"method\": \"Co-immunoprecipitation (FEN1-PCNA-DNMT3a complex), luciferase reporter (miR-200a target sites), methylation-specific PCR, siRNA knockdown\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP for complex; epigenetic mechanism supported by reporter assay but limited mechanistic validation, single lab\",\n      \"pmids\": [\"31266372\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"IGF2BP2 directly recognizes and binds the m6A site on FEN1 mRNA, enhancing FEN1 mRNA stability and thereby maintaining FEN1 protein expression in HCC cells.\",\n      \"method\": \"RNA immunoprecipitation (RIP), m6A site mapping, IGF2BP2 overexpression/knockdown with FEN1 mRNA stability measurement\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — RIP assay with mRNA stability measurement, post-transcriptional regulation of FEN1, single lab single method\",\n      \"pmids\": [\"33224879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FEN1 blockade induces proteasome-mediated degradation of activated ERα and loss of ERα-driven gene expression. FEN1 facilitates coactivator recruitment to the ERα transcriptional complex, thereby impacting ERα transcriptional activity and driving tumor cell proliferation in tamoxifen-resistant breast cancer.\",\n      \"method\": \"FEN1 siRNA depletion, ERα co-immunoprecipitation/coactivator recruitment assays, proteasome inhibitor rescue, small-molecule FEN1 inhibitor screen, proliferation assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple cell-based methods demonstrating FEN1-ERα interaction and functional consequence, independently supported by inhibitor studies\",\n      \"pmids\": [\"32193286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PRMT1 methylates FEN1 as a post-translational modification, maintaining high FEN1 expression levels critical for DNA repair and chemotherapeutic drug resistance in lung cancer cells.\",\n      \"method\": \"PRMT1 knockdown with FEN1 protein level measurement, identification of FEN1 as PRMT1 substrate by co-immunoprecipitation\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single co-IP for substrate identification with knockdown, limited mechanistic detail in abstract, single lab\",\n      \"pmids\": [\"32861926\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"FEN1 regulates cell survival, MAPK p38 phosphorylation, RhoA activation, and actin cytoskeleton reorganization in response to DNA damage triggered by bacterial CDT genotoxin, revealing a crosstalk between DNA damage response and cytoskeleton dynamics mediated by FEN1.\",\n      \"method\": \"S. cerevisiae mutant screen, human cell FEN1 siRNA knockdown, RhoA activation assay, p38 phosphorylation measurement, actin cytoskeleton imaging\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast genetic screen validated in human cells with multiple phenotypic readouts, single lab\",\n      \"pmids\": [\"21807938\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"p53 transcriptionally activates FEN1 expression via a p53 consensus binding site in the fen1 promoter. FEN1 induction by UV-C requires p53 and replication-competent cells. Transgenic FEN1 expression in p53-null cells attenuates UV-C-induced DNA replication inhibition, establishing FEN1 as involved in recovery from stalled replication forks downstream of p53.\",\n      \"method\": \"RT-PCR, Western blot, promoter cloning and reporter assays, ChIP (p53 binding to fen1 promoter), transgenic FEN1 expression in p53-null cells, DNA replication recovery assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter binding demonstrated by reporter and cotransfection with functional rescue, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"16103874\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FEN1 is a structure-specific endo/exonuclease that recognizes and cleaves 5' flap DNA intermediates by threading the free 5' ssDNA through a helical gateway above its two-metal-ion active site while bending the dsDNA ~100°; it functions in Okazaki fragment maturation, long-patch base excision repair (including in mitochondria), stalled replication fork rescue, telomere maintenance, NHEJ, MMEJ, and apoptotic DNA fragmentation, and is regulated by sequential post-translational modifications (arginine methylation suppresses phosphorylation to promote PCNA binding; phosphorylation→SUMOylation→ubiquitination drives proteasomal degradation) as well as by protein partners including PCNA (via two distinct binding modes), WRN, RecQ helicases, the 9-1-1 checkpoint clamp, PARP1 (for recruitment to BER sites), and Dnl4/Lif1/Pol4 in NHEJ.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FEN1 is a structure-specific, sequence-independent nuclease that recognizes, threads, and cleaves 5' flap DNA intermediates, serving as a central enzyme in DNA replication and repair [#0, #17]. It carries flap endonuclease, 5'-3' double-stranded exonuclease, and gap-dependent endonuclease (GEN) activities within a single ~42 kDa enzyme [#1, #12]. Substrate engagement requires the duplex template adjacent to the flap, and the enzyme tracks along the free single-stranded 5' tail to the cleavage point [#1, #3]. Crystallographic and biophysical studies define a mechanism in which FEN1 binds and bends nicked dsDNA ~100°, captures the unpaired 3' flap, and threads the 5' ssDNA through a helical gateway/cap so that double-base unpairing at the scissile phosphate positions it over a two-metal-ion active site for precise incision [#9, #17, #23]. Through these activities FEN1 performs Okazaki fragment maturation and long-patch base excision repair, including LP-BER of oxidized abasic lesions in mitochondrial DNA, and contributes to stalled replication fork rescue, telomere maintenance, NHEJ, microhomology-mediated end joining, homologous recombination, and apoptotic DNA fragmentation [#5, #8, #13, #16, #25]. FEN1 is coordinated by partner proteins: PCNA stimulates its activity and promotes the open-flap conformation through two distinct binding modes, while WRN, RecQ helicases, and the 9-1-1 (Rad9-Hus1-Rad1) checkpoint clamp form alternative complexes that direct repair versus replication functions, and PARP1 is required for FEN1 recruitment to BER sites [#2, #6, #16, #20, #21, #23]. FEN1 activity is timed by sequential post-translational modifications: arginine methylation (Arg192) suppresses Ser187 phosphorylation to favor PCNA binding, whereas an ordered phosphorylation→SUMOylation→ubiquitination cascade drives its proteasomal degradation [#15, #19]. Loss or mutation of FEN1 causes genomic instability, aneuploidy, and cancer: disruption of the FEN1-PCNA interaction or of the FEN1-WRN interaction (E359K, ablating GEN activity) produces fragile telomeres, chromosomal anomalies, and tumors in knock-in mice, and inhibition of FEN1 selectively kills BRCA-deficient cells [#18, #22, #25].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established the foundational identity of FEN1 as a structure-specific endonuclease conserved across species, answering what kind of DNA structures it acts on.\",\n      \"evidence\": \"Gene cloning and in vitro nuclease assays on branched substrates, with conservation to yeast RAD27/RAD2\",\n      \"pmids\": [\"7926735\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic mechanism and metal dependence not yet defined\", \"In vivo pathway roles not yet assigned\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Defined the substrate determinants of flap recognition and showed both endo- and exonuclease activities reside in one enzyme, clarifying how FEN1 selects its targets.\",\n      \"evidence\": \"Mobility shift and nuclease assays with defined flap substrate variants including the adjacent strand\",\n      \"pmids\": [\"7876218\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of dual activity unresolved\", \"Loading mechanism onto substrate undefined\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Identified PCNA as a stimulatory partner and revealed FEN1 loads by tracking along the 5' ssDNA branch, connecting FEN1 to the replication machinery and explaining its directional engagement.\",\n      \"evidence\": \"Physical association assays plus nuclease stimulation assays and footprinting on adducted substrates\",\n      \"pmids\": [\"8668533\", \"8939893\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular structure of the PCNA-FEN1 interface not yet solved\", \"Two-mode PCNA binding not yet distinguished\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Connected FEN1 cleavage failure on repeat-derived secondary structures to repeat expansion, and assigned FEN1 a role in NHEJ via 5' flap processing, expanding its pathway repertoire beyond replication.\",\n      \"evidence\": \"In vitro cleavage with repeat-containing flaps plus yeast genetics; rad27 deletion NHEJ epistasis with flap substrates\",\n      \"pmids\": [\"10635332\", \"9990019\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct in vivo evidence for expansion mechanism in mammals lacking\", \"NHEJ partner proteins not yet identified\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Showed WRN stimulates FEN1 catalytic efficiency independent of substrate binding and even on end-blocked substrates, distinguishing WRN-mediated from PCNA-mediated activation.\",\n      \"evidence\": \"Biochemical kinetics with multiple Okazaki intermediates and streptavidin-blocked substrates\",\n      \"pmids\": [\"12356323\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of WRN stimulation unknown\", \"Cellular context of WRN-FEN1 cooperation not yet established\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Revealed a gap-dependent endonuclease (GEN) activity and cooperation with EndoG in apoptotic DNA fragmentation, broadening FEN1's functional scope to programmed cell death.\",\n      \"evidence\": \"RNAi and genetic epistasis in C. elegans with biochemical GEN characterization\",\n      \"pmids\": [\"12840007\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relevance of GEN activity to mammalian apoptosis not yet shown\", \"Substrate basis of GEN versus FEN activity unresolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Provided the first structural mechanism—3' flap binding, DNA kinking, and helical clamp closure plus an intermolecular beta-sheet linking PCNA and DNA-binding regions—explaining how FEN1 achieves specificity and is coordinated by PCNA.\",\n      \"evidence\": \"X-ray crystallography of FEN1:DNA and PCNA:FEN1-peptide complexes, FRET, mutagenesis\",\n      \"pmids\": [\"14718165\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conformation of the threaded 5' flap not captured\", \"Two distinct PCNA binding modes not structurally reconciled\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Reconstituted FEN1 within an ordered series of NHEJ pairwise interactions with Pol4 and Dnl4/Lif1, defining its biochemical place in end joining of incompatible ends.\",\n      \"evidence\": \"Physical interaction assays and in vitro end-joining reconstitution in S. cerevisiae\",\n      \"pmids\": [\"15342630\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Conservation of these interactions in mammals not demonstrated\", \"Single-lab interaction data without structural detail\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Mapped the GEN activity to the same clamp/ssDNA-interaction region used by FEN activity and implicated the C-terminal extension in downstream duplex contact, unifying the multiple activities mechanistically.\",\n      \"evidence\": \"Comparative kinetics of FEN/EXO/GEN with DNA-binding-deficient mutants and WRN\",\n      \"pmids\": [\"16582103\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural snapshot of GEN engagement absent\", \"In vivo importance of GEN activity not yet tested with separation-of-function alleles\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Placed FEN1 downstream of p53 in the stalled-fork recovery response, establishing transcriptional regulation of FEN1 by a tumor suppressor.\",\n      \"evidence\": \"Promoter reporter assays, ChIP of p53 binding, and replication-recovery rescue in p53-null cells\",\n      \"pmids\": [\"16103874\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct contribution of FEN1 enzymatic activity to fork recovery not dissected\", \"Single-lab transcriptional data\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Localized FEN1 to mitochondria and showed it is required for long-patch BER of oxidized abasic sites in mtDNA, extending its repair role to the mitochondrial genome.\",\n      \"evidence\": \"Subcellular fractionation, immunofluorescence, protease protection, immunodepletion, and RNAi damage-recovery assays\",\n      \"pmids\": [\"18541666\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mitochondrial import mechanism not defined\", \"Mitochondrial partner proteins not identified\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrated that uncoupling of pol beta–FEN1 coordination during LP-BER allows FEN1 to ligate slipped hairpins, providing a repair-pathway mechanism for CAG repeat expansion.\",\n      \"evidence\": \"In vitro repeat-expansion reconstitution in mouse cell extracts dissecting individual enzymes including HMGB1 stimulation\",\n      \"pmids\": [\"19674974\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo confirmation in mammalian tissue lacking\", \"Determinants of pol beta–FEN1 uncoupling unclear\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed arginine methylation at Arg192 suppresses Ser187 phosphorylation to favor PCNA binding and proper foci localization, establishing PTM-controlled timing of FEN1 activity.\",\n      \"evidence\": \"Mass spectrometry, mutagenesis, PCNA co-IP, immunofluorescence, and cell-cycle/mutation-rate readouts\",\n      \"pmids\": [\"20729856\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the responsible methyltransferase not established in this study\", \"Phosphatase counteracting Ser187 unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Distinguished FEN1's telomere maintenance role as dependent on GEN activity and RecQ helicase interaction rather than Okazaki processing, refining which activities matter at telomeres.\",\n      \"evidence\": \"siRNA depletion with fragile/sister telomere assays and activity-specific FEN1 mutants\",\n      \"pmids\": [\"20551483\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which RecQ helicase predominates not resolved\", \"Direct telomeric substrate not defined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Delivered the definitive human FEN1:DNA structural mechanism—~100° bending, dual-flap capture, helical gateway threading, double-base unpairing, and two-metal-ion catalysis—explaining structure-specific, sequence-independent incision.\",\n      \"evidence\": \"X-ray crystallography of FEN1:DNA substrate and product complexes with mutagenesis and functional assays\",\n      \"pmids\": [\"21496641\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamics of gateway opening not captured statically\", \"Allosteric coupling to PCNA not fully resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Linked the FEN1-PCNA interaction directly to genome stability and cancer in vivo through a separation-of-function knock-in, demonstrating causal consequence of losing this interaction.\",\n      \"evidence\": \"FFAA knock-in mouse with BER/Okazaki biochemistry, cytogenetics, checkpoint, and tumor readouts\",\n      \"pmids\": [\"21383776\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specific tumor spectrum not fully explained\", \"Contribution of residual activities not isolated\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Uncovered a crosstalk between FEN1-mediated DNA damage response and cytoskeletal signaling (p38, RhoA, actin) in response to genotoxin, broadening FEN1's cellular consequences.\",\n      \"evidence\": \"Yeast mutant screen validated by human FEN1 siRNA with signaling and cytoskeleton readouts\",\n      \"pmids\": [\"21807938\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular link between FEN1 and signaling not defined\", \"Generality beyond CDT genotoxin untested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined a sequential phosphorylation→SUMOylation→ubiquitination cascade controlling FEN1 proteasomal degradation, providing the off-switch that times FEN1 turnover with the cell cycle.\",\n      \"evidence\": \"PTM biochemistry, mutant FEN1 expression, proteasome inhibitor and cell-cycle analyses\",\n      \"pmids\": [\"22749529\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific E3 ligase and SUMO ligase not identified here\", \"Spatial coordination with chromatin not defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed FEN1 forms a more stable complex with the 9-1-1 checkpoint clamp than with PCNA, suggesting clamp-specific partitioning between repair and replication.\",\n      \"evidence\": \"Single-particle EM reconstruction (18 Å) plus molecular dynamics simulations\",\n      \"pmids\": [\"22586102\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"High-resolution structure of the 9-1-1/FEN1 complex lacking\", \"Functional consequence of differential stability not tested in vivo\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established that PARP1 is required for FEN1 recruitment to BER sites in living cells, defining the recruitment step for FEN1 at damage.\",\n      \"evidence\": \"Endogenous FEN1-YFP knock-in, live-cell laser microirradiation, and PARP1 inhibition\",\n      \"pmids\": [\"22810208\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct PARP1-FEN1 physical contact not demonstrated\", \"Role of PAR chains versus protein interaction unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Revealed at single-molecule level that FEN1 bends and locks DNA into an open-flap state and that PCNA promotes 5' ssDNA threading through the gateway, mechanistically explaining PCNA stimulation.\",\n      \"evidence\": \"Single-molecule FRET, protein-induced fluorescence enhancement, and ensemble FRET\",\n      \"pmids\": [\"24234453\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinetics relative to in vivo replication rates not established\", \"Threading intermediate not structurally captured\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated via the E359K germline mutation that the FEN1-WRN interaction and GEN activity are jointly required for stalled-fork resolution and tumor suppression, separating these from flap endonuclease activity.\",\n      \"evidence\": \"Knock-in mouse, co-IP, activity assays, cytogenetics, and tumor incidence\",\n      \"pmids\": [\"24608430\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis for E359K disrupting both interaction and GEN activity unresolved\", \"Human germline relevance not established\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed the cancer-associated L209P mutation abolishes all nuclease activities while retaining DNA binding, acting dominant-negatively to impair wild-type FEN1 and drive transformation.\",\n      \"evidence\": \"Biochemical activity/binding assays, dominant-negative cellular expression, in vitro BER, and xenograft\",\n      \"pmids\": [\"27270424\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of catalytic-dead-but-binding phenotype not defined\", \"Human tumor frequency of L209P unestablished\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified FEN1 flap endonuclease activity as a synthetic-lethal vulnerability in BRCA-deficient cells via MMEJ, nominating FEN1 inhibition as a targeted therapeutic strategy.\",\n      \"evidence\": \"CRISPR screens in isogenic BRCA2-deficient lines, MMEJ reporter, activity-specific mutants, and a small-molecule inhibitor\",\n      \"pmids\": [\"30686591\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"FEN1 partners in MMEJ not identified\", \"Inhibitor specificity and in vivo efficacy not fully defined here\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Proposed a non-canonical oncogenic role in which a FEN1/PCNA/DNMT3a complex epigenetically suppresses miR-200a-5p to derepress MET/EGFR, linking FEN1 to breast cancer proliferation.\",\n      \"evidence\": \"Co-IP, luciferase reporters, methylation-specific PCR, and siRNA knockdown\",\n      \"pmids\": [\"31266372\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP without reciprocal or structural validation of the complex\", \"Direct DNA methylation role of FEN1 not mechanistically established\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified post-transcriptional and transcriptional-cofactor roles supporting FEN1's oncogenic expression—m6A-IGF2BP2 stabilization of FEN1 mRNA, PRMT1 methylation maintaining FEN1 levels, and FEN1 facilitating ERα coactivator recruitment.\",\n      \"evidence\": \"RIP and mRNA stability (IGF2BP2), co-IP and knockdown (PRMT1), and ERα co-IP/coactivator and inhibitor assays\",\n      \"pmids\": [\"33224879\", \"32861926\", \"32193286\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"IGF2BP2 and PRMT1 findings rest on single-method, single-lab data\", \"Mechanism of FEN1-ERα coactivator facilitation not structurally defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How FEN1's many activities and partner complexes are spatially and temporally partitioned among replication, BER, telomere maintenance, end joining, and its proposed transcriptional/epigenetic roles in vivo remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model assigning specific complexes to specific pathways in cells\", \"Non-canonical transcriptional/epigenetic roles lack high-confidence mechanistic validation\", \"The methyltransferase, E3, and SUMO ligase enzymes of the PTM cascade not all identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140097\", \"supporting_discovery_ids\": [0, 1, 12, 17]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [3, 17, 24]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [15, 21]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [13, 18, 25]},\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [2, 6, 15]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"complexes\": [\"9-1-1 (Rad9-Hus1-Rad1) checkpoint clamp\", \"FEN1/PCNA/DNMT3a complex\"],\n    \"partners\": [\"PCNA\", \"WRN\", \"RAD9-HUS1-RAD1\", \"PARP1\", \"Pol4\", \"Dnl4/Lif1\", \"PRMT1\", \"IGF2BP2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}