{"gene":"RAD1","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1993,"finding":"Purified yeast Rad1 and Rad10 proteins form a complex that possesses endonuclease activity specifically degrading single-stranded DNA by an endonucleolytic mechanism; this activity is presumed to remove non-homologous regions during mitotic recombination and to incise damaged DNA during nucleotide excision repair.","method":"In vitro biochemical assay with purified proteins; single-stranded DNA endonuclease activity reconstituted from purified Rad1 and Rad10","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro endonuclease activity with purified proteins, replicated in multiple subsequent studies","pmids":["8479526"],"is_preprint":false},{"year":1993,"finding":"Purified yeast Rad1-Rad10 endonuclease activity on single-stranded and double-stranded DNA produces 3'-hydroxyl and 5'-phosphate termini; activity on double-stranded DNA is strongly dependent on negative superhelicity.","method":"In vitro biochemical characterization with purified Rad1 and Rad10 proteins; agarose gel electrophoresis and TCA precipitation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — purified proteins, multiple substrates and orthogonal biochemical methods in a single rigorous study","pmids":["8253764"],"is_preprint":false},{"year":1994,"finding":"Rad1-Rad10 complex cleaves model recombination/repair intermediates specifically at duplex-single-strand junctions, acting only on the strand containing the 3' single-stranded tail; this defines the biochemical basis for its role in removing nonhomologous tails during recombination and for 5' incision during NER.","method":"In vitro cleavage assay using model recombination and repair intermediate substrates with purified Rad1-Rad10","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with defined substrates, supported by genetic evidence in same paper","pmids":["8091230"],"is_preprint":false},{"year":1994,"finding":"Yeast Rad1 protein binds specifically to Holliday junctions and, in the presence of magnesium, catalyzes endonucleolytic cleavage of the junction independently of Rad10, identifying Rad1 as the catalytic subunit of the Rad1/Rad10 endonuclease.","method":"In vitro binding and cleavage assay with purified Rad1 protein and synthetic Holliday junction substrates","journal":"Nature","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — single lab in vitro assay; note that another paper (PMID:7559571) using independently purified proteins failed to reproduce Holliday junction interaction, reducing confidence","pmids":["7935767"],"is_preprint":false},{"year":1995,"finding":"Purified Rad1-Rad10 complex incises a synthetic bubble DNA substrate at the 5'-side of the centrally unpaired region; when combined with XPG, dual incisions at both ends of the bubble are observed, reconstituting the dual incision step of nucleotide excision repair in vitro. Separately, Rad1 failed to show interaction with synthetic Holliday junctions in this study (negative result).","method":"In vitro incision assay with purified Rad1-Rad10 and XPG on bubble DNA substrates; synthetic Holliday junction binding assay (negative)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — dual incision reconstituted with purified proteins; independently replicated the NER incision mechanism","pmids":["7559571"],"is_preprint":false},{"year":1992,"finding":"Yeast Rad1 and Rad10 proteins form a stable, specific complex in vitro and in vivo; the interaction is resistant to 1 M NaCl and low SDS; a rad1 mutant allele encoding a protein that fails to bind Rad10 is as defective in DNA repair and recombination as a null mutant, demonstrating that complex formation is essential for both biological activities.","method":"Co-immunoprecipitation from yeast cell extracts; in vitro co-translation and co-immunoprecipitation; mutational analysis (interaction-defective rad1 allele)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — reciprocal Co-IP in vivo and in vitro, plus loss-of-interaction mutant with matching loss-of-function phenotype; replicated by multiple labs","pmids":["1518857"],"is_preprint":false},{"year":1992,"finding":"Stable and specific in vitro interaction between Rad1 and Rad10 proteins was mapped: the Rad10-binding domain of Rad1 maps to the C-terminal region, and the Rad1-binding domain of Rad10 also maps to its C-terminal region; these domains are evolutionarily conserved and hydrophobic.","method":"In vitro co-immunoprecipitation with in vitro translated proteins; domain mapping by truncation analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro domain mapping with multiple truncations, replicated across labs","pmids":["1620114"],"is_preprint":false},{"year":1993,"finding":"Rad1 and Rad10 form a constitutive complex in the cell nucleus; the Rad10-binding domain of Rad1 maps to amino acids 809–997, and the Rad1-binding domain of Rad10 maps to amino acids 90–210; these domains are hydrophobic and evolutionarily conserved.","method":"Yeast two-hybrid assay; domain mapping with truncation constructs","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — two-hybrid interaction mapping, consistent with in vitro biochemical data from other labs","pmids":["8361362"],"is_preprint":false},{"year":1992,"finding":"In Saccharomyces cerevisiae, Rad1 is required to remove nonhomologous DNA sequences (~60 bp) from the 3' ends of recombining DNA during double-strand break repair; recombination is restored when the ends are made homologous, placing Rad1 in the 3'-end processing step during single-strand annealing and gene conversion.","method":"Genetic epistasis using HO endonuclease-induced DSBs in rad1 mutant yeast; Southern blot analysis of recombination products","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean loss-of-function with specific molecular readout, foundational genetic study replicated extensively","pmids":["1411547"],"is_preprint":false},{"year":1995,"finding":"Among nucleotide excision repair genes, only RAD1 and RAD10 (not RAD2, RAD3, RAD14, RAD7, or RAD16) are required for removing nonhomologous sequences from DSB ends during gap repair and single-strand annealing, demonstrating a specific role for Rad1-Rad10 in this recombination sub-pathway.","method":"Genetic analysis of HO-induced DSB repair in multiple NER gene deletion strains; physical monitoring by Southern blot","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic genetic epistasis with multiple mutant combinations, replicated across labs","pmids":["7891718"],"is_preprint":false},{"year":1999,"finding":"Human hRad1 and hHus1 associate in a complex that interacts with a highly modified (phosphorylated) form of hRad9; hHus1 and hRad1 do not associate with hRad17; hRad9 is phosphorylated in response to DNA damage.","method":"Co-immunoprecipitation from human cell extracts; Western blotting","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP from human cells showing complex formation; single lab but consistent with yeast data","pmids":["9872989"],"is_preprint":false},{"year":1999,"finding":"Human hRAD9 physically associates with hRAD1 and hHUS1; hRAD1 and hHUS1 also interact with each other; hRAD9 is a nuclear phosphoprotein present in multiple phosphorylation forms in vivo.","method":"Co-immunoprecipitation from human cells; nuclear fractionation; Western blot","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP, nuclear fractionation, single lab; confirmed by independent labs","pmids":["10359610"],"is_preprint":false},{"year":2001,"finding":"The human hRad9-hHus1-hRad1 (9-1-1) complex is a stable, discrete heterotrimeric complex of ~160 kDa in which: the N-terminus of hRad9 interacts with hRad1, the N-terminus of hRad1 interacts with hHus1, and the N-terminus of hHus1 interacts with the C-terminus of hRad9's PCNA-like region; approximately half the cellular hRad1 participates in this complex.","method":"Biochemical fractionation; reconstitution by co-expression in heterologous system; co-immunoprecipitation with differentially tagged proteins; size-exclusion chromatography","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — complex reconstituted in heterologous system, reciprocal Co-IP with domain mapping, multiple orthogonal methods","pmids":["11340080"],"is_preprint":false},{"year":2000,"finding":"Computational structure prediction indicates that human Rad1 (and its yeast/fission yeast orthologs) shares a PCNA-like fold; the three proteins Rad9, Hus1, and Rad1 are predicted to form a heterotrimeric PCNA-like ring, with a defined order within the ring and identified contact regions between subunits.","method":"Computational fold recognition, comparative modeling, and generalized sequence profiles; structural prediction validated against existing biochemical data","journal":"Nucleic acids research","confidence":"Low","confidence_rationale":"Tier 4 / Moderate — computational prediction only; later confirmed experimentally by crystal structures","pmids":["10871397"],"is_preprint":false},{"year":2009,"finding":"Crystal structure of the human 9-1-1 (Rad9-Hus1-Rad1) complex reveals a toroidal PCNA-like heterotrimeric ring; the structure shows significant differences among the three subunits at sites implicated in clamp loader binding and ligand binding; biochemical analysis identifies a single repair enzyme-binding site on 9-1-1 that is competitively blocked by p21(cip1/waf1).","method":"X-ray crystallography; biochemical competition assay with p21","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional biochemical validation; independently confirmed by two other crystal structures published the same year","pmids":["19446481"],"is_preprint":false},{"year":2009,"finding":"Crystal structure of the human Rad9(1-272)-Hus1-Rad1 complex at 2.5 Å resolution confirms the closed toroidal architecture; co-crystallization reveals that an FEN1 PIP-box peptide binds to the interdomain connecting loop (IDC loop) of hRad1, providing the molecular basis for damage repair-specific activity of 9-1-1 distinct from PCNA.","method":"X-ray crystallography at 2.5 Å; co-crystallization with FEN1 PIP-box peptide; biochemical assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with co-crystal validation of FEN1 binding site on Rad1 IDC loop","pmids":["19535328"],"is_preprint":false},{"year":2009,"finding":"Crystal structure of human Rad9(1-272)-Hus1-Rad1 at 2.5 Å resolution shows the 9-1-1 complex forms a closed ring; the full-length 9-1-1 complex (with Rad9 C-terminal tail) does not form a stable complex with 5' recessed DNA, but the Rad9(1-272) truncation does, indicating that the C-terminal tail of Rad9 regulates DNA binding by 9-1-1.","method":"X-ray crystallography; DNA-binding assay comparing full-length and truncated 9-1-1","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with functional DNA binding validation; single lab but two orthogonal methods","pmids":["19464297"],"is_preprint":false},{"year":2000,"finding":"Human hRad17 interacts with the PCNA-like checkpoint proteins hRad1, hRad9, and hHus1 in a manner resembling the RFC–PCNA clamp loader interaction; DNA damage affects the association of hRad17 with the clamp-like proteins; mutational analysis of hRad1 and hRad17 confirms properties similar to RFC–PCNA interaction.","method":"Co-immunoprecipitation from human cells; mutational analysis of interaction surfaces; Western blot","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP with mutational validation, single lab but multiple constructs","pmids":["10884395"],"is_preprint":false},{"year":2007,"finding":"The 9-1-1 complex activates Chk1 via binding of Rad9's C-terminal tail to TopBP1, which then stimulates ATR-mediated Chk1 phosphorylation through TopBP1's activation domain (AD); fusion of the AD to PCNA or histone H2B bypasses the requirement for the 9-1-1 clamp, demonstrating that the primary role of 9-1-1 in Chk1 activation is to localize TopBP1's AD to stalled replication forks.","method":"Co-immunoprecipitation; TopBP1-PCNA and TopBP1-H2B fusion bypass experiments in human cells; Chk1 phosphorylation assays","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — epistasis via bypass fusion constructs plus Co-IP; replicated by independent lab (PMID:17636252)","pmids":["17575048"],"is_preprint":false},{"year":2007,"finding":"The 9-1-1 complex regulates the interaction of TopBP1 with ATR-ATRIP in Xenopus egg extracts; the BRCT I-II region of TopBP1 binds specifically to the 9-1-1 complex via the C-terminal domain of Rad9, and this interaction requires phosphorylation of Rad9 Ser-373; mutation of TopBP1 BRCT I-II or Rad9 Ser-373→Ala causes checkpoint defects.","method":"Co-immunoprecipitation from Xenopus egg extracts; checkpoint assays with mutant proteins; phospho-specific analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — Xenopus biochemical reconstitution with phospho-site mutagenesis, functional checkpoint validation; independent replication of 9-1-1/TopBP1 interaction","pmids":["17636252"],"is_preprint":false},{"year":2010,"finding":"Casein kinase 2 (CK2) phosphorylates Ser-341 and Ser-387 in the C-terminal tail of human Rad9; phosphorylation at these sites (particularly Ser-387) is required for the 9-1-1 complex to physically interact with TopBP1 and for efficient ATR-dependent checkpoint activation; cells expressing phospho-deficient Rad9 (S341A/S387A) are hypersensitive to UV and MMS.","method":"In vitro kinase assay with purified CK2 and 9-1-1; Co-IP; mutagenesis; UV/MMS sensitivity assays","journal":"Genes to cells : devoted to molecular & cellular mechanisms","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro kinase assay plus Co-IP plus functional complementation, single lab but multiple orthogonal methods","pmids":["20545769"],"is_preprint":false},{"year":2010,"finding":"Rad17 mediates the interaction between 9-1-1 and TopBP1 in Xenopus egg extracts; ATP binding to Rad17 is essential for 9-1-1–TopBP1 association, and ATP hydrolysis by Rad17 is required for 9-1-1 loading onto DNA and for elevated TopBP1 chromatin accumulation; a 9-1-1 mutant unable to bind TopBP1 still promotes normal TopBP1 chromatin accumulation, placing Rad17 upstream.","method":"Xenopus egg extract biochemistry; Rad17 ATPase mutants; 9-1-1 TopBP1-binding mutant; chromatin fractionation assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple Xenopus mutant combinations establishing mechanism; single lab but multiple orthogonal approaches","pmids":["20110345"],"is_preprint":false},{"year":2002,"finding":"Genotoxin-induced chromatin association of the 9-1-1 complex does not require ATM, ATR, or DNA-PK catalytic activity, does not require Rad9 Ser-272 phosphorylation, and does not require DNA replication, establishing that 9-1-1 chromatin loading is a proximal, kinase-independent event in the checkpoint cascade.","method":"Chromatin fractionation assay in human cells with pharmacological kinase inhibitors and phospho-site mutants; flow cytometry","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple inhibitor conditions and mutants; single lab","pmids":["12228248"],"is_preprint":false},{"year":2004,"finding":"Loss of RAD1 in mammalian cells destabilizes Rad9 and Hus1, causing disintegration of the 9-1-1 complex; Rad1 depletion impairs ATR-dependent (but not ATM-dependent) Chk1 activation, causes radioresistant DNA synthesis (RDS), and results in chromosomal abnormalities, establishing Rad1 as essential for ATR-dependent checkpoint signaling.","method":"siRNA knockdown of RAD1; Western blot for complex stability; Chk1 phosphorylation assays; DNA fiber assays; cytogenetics","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean KD with multiple orthogonal functional readouts; single lab","pmids":["15184880"],"is_preprint":false},{"year":2004,"finding":"The human 9-1-1 complex physically interacts with DNA polymerase beta (Pol β) in vitro, stimulates its activity by increasing its affinity for the primer-template, and enhances strand displacement synthesis; 9-1-1 does not stimulate DNA polymerase lambda, alpha, or delta.","method":"In vitro pull-down; DNA polymerase activity assays with and without 9-1-1; primer extension assays","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro reconstitution with specificity controls; single lab","pmids":["15314187"],"is_preprint":false},{"year":2004,"finding":"The human 9-1-1 complex binds and stimulates flap endonuclease 1 (FEN1) on flap, nick, and gapped substrates; stimulation requires 9-1-1 entry to the double-stranded region; 9-1-1 does not substitute for PCNA in stimulating DNA polymerase beta, making it a damage-specific FEN1 activator.","method":"In vitro FEN1 activity assay with purified 9-1-1; cleavage assays on multiple substrates","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified proteins, multiple substrates, specificity controls; replicated by additional labs","pmids":["15556996"],"is_preprint":false},{"year":2005,"finding":"The human 9-1-1 complex interacts with and stimulates DNA ligase I; 9-1-1 improves the binding of DNA ligase I to nicked double-stranded DNA; UV irradiation stimulates 9-1-1–ligase I complex formation in cells; stimulation is specific for ligase I and does not require encirclement of the DNA substrate (unlike PCNA).","method":"Co-immunoprecipitation from human cells; in vitro ligation assay; UV irradiation stimulation experiment","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP from cells plus in vitro functional assay; single lab","pmids":["15871698"],"is_preprint":false},{"year":2006,"finding":"The 9-1-1 complex stimulates DNA ligase I by improving its binding to nicked DNA; high concentrations of casein kinase II inhibit ligase I but do not prevent 9-1-1-mediated stimulation; unlike PCNA, 9-1-1 stimulates DNA ligase I equally on linear and circular substrates, indicating encirclement is not required.","method":"In vitro ligation assay; DNA binding assay; kinase inhibition experiment","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mechanistic comparisons; single lab","pmids":["16731526"],"is_preprint":false},{"year":2006,"finding":"Human MYH DNA glycosylase interacts with hRad1 and hHus1 (but not hRad9) of the 9-1-1 complex; the major interaction site maps to residues 295–350 of hMYH; hHus1 and the 9-1-1 complex enhance MYH glycosylase activity; the hMYH-hHus1 interaction is enhanced after ionizing radiation.","method":"Co-immunoprecipitation; in vitro pulldown; glycosylase activity assay with and without 9-1-1; mutagenesis of interaction sites","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus in vitro functional assay plus mutagenesis; single lab","pmids":["16879101"],"is_preprint":false},{"year":2007,"finding":"The human 9-1-1 complex interacts with hNEIL1 DNA glycosylase; residues 290–350 of hNEIL1 are important for 9-1-1 association; hHus1, hRad1, and hRad9 individually and as a complex significantly stimulate hNEIL1 glycosylase activity; a fraction of hNEIL1 nuclear foci co-localizes with hRad9 foci after hydrogen peroxide treatment.","method":"Co-immunoprecipitation; in vitro glycosylase stimulation assay; immunofluorescence co-localization","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus in vitro activity assay plus localization; single lab, three orthogonal methods","pmids":["17395641"],"is_preprint":false},{"year":2007,"finding":"The human 9-1-1 complex interacts with thymine DNA glycosylase (hTDG); hHus1 interacting domain maps to residues 67–110 of hTDG (Val74 critical); hHus1, hRad1, hRad9 individually and as a complex stimulate hTDG glycosylase activity; the hRad9-hTDG interaction is enhanced after MNNG treatment.","method":"Co-immunoprecipitation; mutagenesis; in vitro glycosylase activity assay; immunofluorescence","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with mutagenesis plus in vitro functional assay; single lab","pmids":["17855402"],"is_preprint":false},{"year":2007,"finding":"The 9-1-1 complex interacts with APE1 in vitro and in vivo, stimulates APE1 AP-endonuclease activity, and stimulates long-patch base excision repair (LP-BER) reconstituted in vitro by specifically enhancing the activities of APE1 and Pol β as early LP-BER components.","method":"Co-immunoprecipitation; in vitro AP-endonuclease assay; LP-BER reconstitution assay","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro reconstitution with multiple substrates plus Co-IP; single lab","pmids":["17426133"],"is_preprint":false},{"year":2005,"finding":"The 9-1-1 complex independently binds and activates FEN1, and this stimulation is abolished by acetylation of FEN1 by p300-HAT, whereas PCNA stimulation of FEN1 is unaffected by acetylation, suggesting independent regulatory mechanisms for the two clamps.","method":"In vitro FEN1 activity assay; p300-mediated acetylation of FEN1; comparison with PCNA stimulation","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with post-translational modification comparison; single lab","pmids":["16216273"],"is_preprint":false},{"year":2005,"finding":"The 9-1-1 complex directly interacts with RPA in human cells; this interaction is mediated by Rad9 binding to RPA70 and RPA32 subunits; UV or camptothecin treatment stimulates 9-1-1–RPA interaction; RPA knockdown by siRNA blocks damage-dependent chromatin association of 9-1-1 and also inhibits 9-1-1 complex formation.","method":"Co-immunoprecipitation; siRNA knockdown; immunofluorescence co-localization; chromatin fractionation","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus functional siRNA experiment; single lab","pmids":["15897895"],"is_preprint":false},{"year":2004,"finding":"In Schizosaccharomyces pombe, Hus1 associates in a complex with Rad9 and Rad1; this Rad1-Rad9-Hus1 complex is detectable in soluble extracts; nuclear localization of Hus1 depends on Rad17; Rad17 forms a separate complex in soluble extracts distinct from the Rad1-Rad9-Hus1 complex but shows transient interaction with Rad1.","method":"Immunoprecipitation from S. pombe extracts; indirect immunofluorescence; two-hybrid assay; in vitro association","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — multiple methods including IP, immunofluorescence, two-hybrid; single lab","pmids":["10648611"],"is_preprint":false},{"year":1996,"finding":"Mismatch repair genes MSH2 and MSH3 function in the RAD1-RAD10 recombination pathway in yeast; msh3Δ has an effect similar to rad1Δ and rad10Δ on recombination between his3 duplications and homologous integration; epistasis analysis places MSH2 and MSH3 in the RAD1-RAD10 pathway.","method":"Genetic epistasis analysis; recombination frequency measurement in single and double mutants","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis with multiple mutant combinations; single lab","pmids":["8849883"],"is_preprint":false},{"year":2003,"finding":"Yeast Rad1 (with Mre11 and Rad50) defines a Ku-independent microhomology-mediated end joining (MMEJ) pathway for repairing DSBs lacking complementary end sequences; this MMEJ produces deletions annealed by ~8–10 bp microhomology at junctions and is Ku-independent but strongly dependent on Mre11, Rad50, and Rad1.","method":"Genetic analysis with HO-induced DSBs in yku70Δ rad1Δ and mre11Δ mutants; Southern blot analysis of repair products","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with defined molecular readout; single lab","pmids":["14612421"],"is_preprint":false},{"year":2002,"finding":"The yeast Rad1-Rad10 structure-specific endonuclease and tyrosyl-DNA phosphodiesterase Tdp1 function as primary redundant pathways for repairing Top1 replicative damage (Top1 cleavage complexes); the catalytic point mutant rad1-D869A (Rad1-Rad10 nuclease-dead) is as sensitive as rad1Δ, confirming endonuclease activity is required; the Rad1-Rad10 pathway depends on RAD52, RAD51, RAD50, RAD59, and SRS2 but is independent of other NER genes.","method":"Genetic analysis with camptothecin sensitivity; use of catalytic point mutant rad1-D869A; epistasis with multiple recombination genes","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — catalytic point mutant establishes endonuclease requirement; extensive epistasis mapping; confirmed by multiple genetic interactions","pmids":["12368472"],"is_preprint":false},{"year":2004,"finding":"Yeast Rad1-Rad10 nuclease is required for removing 3'-blocked termini (including 3'-phosphoglycolate) from DNA strand breaks induced by H2O2; Rad1-Rad10 in vitro efficiently cleaves DNA modified with a 3'-phosphoglycolate terminus; the nuclease acts redundantly with Apn1 and Apn2 in this 3'-end processing pathway.","method":"In vitro cleavage assay with 3'-phosphoglycolate-modified substrates; genetic analysis (apn1 apn2 rad1 triple mutants); H2O2 sensitivity experiments","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro cleavage of modified substrate plus genetic validation; single lab with two orthogonal approaches","pmids":["15371342"],"is_preprint":false},{"year":2006,"finding":"Complex formation between Rad1-Rad10 nuclease and the damage recognition protein Rad14 is essential for Rad1-Rad10 to function in NER in vivo; two rad1 mutations were identified that render cells as UV-sensitive as rad1Δ but do not affect Rad1's recombination function, and these mutations abolish Rad14 interaction without affecting Rad10 interaction, establishing that Rad14 binding provides damage-site targeting for Rad1-Rad10.","method":"Mutational analysis of RAD1; in vivo UV sensitivity; biochemical complex formation assays; separation-of-function mutants","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — separation-of-function mutations with biochemical and genetic validation; single lab with two orthogonal methods","pmids":["16428464"],"is_preprint":false},{"year":2008,"finding":"Saw1 (Yal027Wp) is required for Rad1/Rad10-dependent 3' flap cleavage during single-strand annealing (SSA); Saw1 physically interacts with Rad1/Rad10, Msh2/Msh3, and Rad52; Saw1 mutants that fail to interact with Rad1 but retain Rad52/Msh2 interaction are specifically defective in 3' flap removal; deletion of SAW1 abolishes association of Rad1 at SSA intermediates in vivo.","method":"Microarray-based genetic screen; Co-IP; physical interaction mapping; chromatin immunoprecipitation (ChIP); SSA assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (genetic screen, Co-IP, ChIP, separation-of-function mutants); replicated in follow-up study","pmids":["18471978"],"is_preprint":false},{"year":2010,"finding":"Mec1/Tel1-dependent phosphorylation of Slx4 at Thr113 is required for efficient cleavage of 3' non-homologous DNA tails by Rad1-Rad10 during single-strand annealing and homologous recombination; Slx4 is recruited to 3' NH tails during DSB repair independently of its phosphorylation; deletion of both MEC1 and TEL1 severely reduces NH tail cleavage.","method":"Genetic analysis; site-directed mutagenesis of Slx4 phosphorylation sites; ChIP; SSA assay","journal":"DNA repair","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-site mutagenesis with functional readout; single lab","pmids":["20382573"],"is_preprint":false},{"year":2013,"finding":"Saw1 is a structure-specific DNA binding protein with high affinity for splayed arm and 3'-flap DNAs; Saw1 physically interacts with Rad1 and facilitates targeting of Rad1 to 3'-tailed substrates in vivo and in vitro; Saw1 enhances 3'-tail cleavage by Rad1/Rad10 in a purified reconstituted system.","method":"In vitro DNA binding assay; in vitro cleavage assay with purified Rad1/Rad10 and Saw1; ChIP; Co-IP","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro reconstitution with purified proteins plus in vivo validation; single lab, multiple orthogonal methods","pmids":["23299942"],"is_preprint":false},{"year":2003,"finding":"In fission yeast, damage-induced Crb2 (Rad9/53BP1 homolog) nuclear foci form independently of Rad1, Rad3, and Rad17 complexes, but these complexes are required for persistent (long-lasting) retention of Crb2 at DSB sites, placing the 9-1-1/Rad3 complexes in the retention rather than initial recruitment of Crb2.","method":"Live-cell fluorescence microscopy of Crb2-GFP in rad1, rad3, rad17 mutants; time-course analysis of foci persistence","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional interpretation; single lab","pmids":["12917337"],"is_preprint":false},{"year":2003,"finding":"Mus81-Mms4 and Rad1-Rad10 are homologous structure-specific endonucleases with distinct cleavage site selection: Rad1-Rad10 cleavage site is determined by the branch point, while Mus81-Mms4 cleavage is determined by the 5' end of the strand at the flap junction; substrates lacking a 5' end near the flap are cleaved poorly by Mus81-Mms4 but well by Rad1-Rad10.","method":"In vitro cleavage assay with defined substrates comparing Mus81-Mms4 and Rad1-Rad10 endonucleases","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — comparative in vitro biochemistry with defined substrates; single lab","pmids":["12724407"],"is_preprint":false},{"year":2012,"finding":"The Rad1-Rad10 nuclease promotes crossover and non-crossover recombinants between ectopic sequences; crossover products are absent only from the mus81Δ rad1Δ yen1Δ triple mutant, indicating that Rad1-Rad10 participates with Mus81-Mms4 and Yen1 in processing recombination intermediates between dispersed repeats; Rad1-dependent joint molecules accumulate in mus81Δ yen1Δ mutants.","method":"Genetic analysis; physical monitoring of recombination intermediates by Southern blot; triple mutant analysis","journal":"Nature structural & molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — physical monitoring of intermediates plus genetic epistasis; single lab","pmids":["22885325"],"is_preprint":false},{"year":2013,"finding":"In mouse testis, HUS1 loss (in 9-1-1) causes persistent meiotic DSBs, synapsis defects, and spermatocyte depletion; RAD9 localizes to RAD51-containing foci in a HUS1-dependent manner; RAD1 has a broader meiotic chromosome distribution that only partially overlaps with RAD9, and RAD1 localization to the XY body and unsynapsed autosomes is HUS1-independent, suggesting RAD1 can function through an alternative mechanism outside the canonical 9-1-1 complex.","method":"Conditional Hus1 knockout in mouse testis; immunofluorescence of meiotic chromosome spreads; phenotypic analysis","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with direct localization experiments; single study","pmids":["23468651"],"is_preprint":false},{"year":1998,"finding":"Human HRAD1 (HisHrad1A) has 3'→5' exonuclease activity when expressed and purified from bacteria; the shorter splice variant HisHrad1B lacks this activity; HRAD1 is located on chromosome 5p13.2-13.3.","method":"Recombinant protein expression and purification; in vitro exonuclease assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro biochemical assay with purified recombinant protein; single lab, single paper","pmids":["9660799"],"is_preprint":false},{"year":1998,"finding":"Human HRAD1 complements UV sensitivity and G2 checkpoint defects of S. pombe rad1 mutants, establishing that HRAD1 is the functional human ortholog of S. pombe rad1+; HRAD1 protein localizes predominantly to the nucleus and is expressed at high levels in proliferative tissues; mouse Rad1 is associated with meiotic chromosomes during spermatogenesis prophase I.","method":"Complementation assay in S. pombe rad1 mutant; nuclear localization by immunofluorescence; meiotic chromosome spread immunostaining","journal":"Genes & development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional complementation plus direct localization experiments; single lab","pmids":["9716408"],"is_preprint":false},{"year":2006,"finding":"The mammalian 9-1-1 complex localizes to telomeres in human and mouse cells; HUS1-deficient mouse fibroblasts and thymocytes show severe telomere shortening; 9-1-1 associates with catalytically competent telomerase in cell lysates and acts as a positive regulator of telomerase DNA polymerase activity.","method":"Chromatin immunoprecipitation at telomeres; telomere length measurement (Q-FISH and Southern); Co-IP with telomerase; telomerase activity assay","journal":"Current biology : CB","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus telomerase activity assay plus conditional KO phenotype; single lab","pmids":["16890531"],"is_preprint":false},{"year":2004,"finding":"hRad9, hHus1, and hRad1 (9-1-1 complex) localize as constitutive components of ALT-associated PML bodies (APBs) in ALT cells, colocalizing with telomeric DNA and γ-H2AX; this places the 9-1-1 complex at telomeric DSBs in ALT cells.","method":"Immunofluorescence and FISH co-localization; ChIP at telomeres","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct localization experiments; single lab","pmids":["15075340"],"is_preprint":false}],"current_model":"RAD1 encodes a conserved checkpoint and DNA repair protein that functions in two distinct capacities: (1) as part of the heterotrimeric 9-1-1 (RAD9-HUS1-RAD1) PCNA-like sliding clamp, which is loaded onto damaged DNA by the RAD17-RFC clamp loader, recruits TopBP1 (via phosphorylated RAD9) to stimulate ATR-mediated CHK1 activation, and serves as a scaffold that stimulates multiple base excision repair enzymes (Pol β, FEN1, DNA ligase I, APE1, NEIL1, TDG, MYH); and (2) in complex with RAD10/ERCC1 as a structure-specific endonuclease that cleaves duplex-single-strand junctions (cutting the 3'-tailed strand) to perform the 5' incision in nucleotide excision repair, remove nonhomologous 3' tails during single-strand annealing and gene conversion DSB repair, and process 3'-blocked termini from oxidative strand breaks."},"narrative":{"mechanistic_narrative":"RAD1 is a conserved DNA repair and checkpoint protein that operates through two structurally and functionally distinct assemblies. In nucleotide excision repair and recombination, Rad1 partners with Rad10 to form a structure-specific endonuclease that degrades single-stranded DNA and cleaves duplex–single-strand junctions on the 3'-tailed strand [PMID:8479526, PMID:8091230]; this activity generates 3'-hydroxyl/5'-phosphate termini and performs the 5' incision during NER, reconstituting dual incision when combined with XPG [PMID:8253764, PMID:7559571]. Stable Rad1–Rad10 complex formation, mediated by conserved C-terminal hydrophobic domains, is essential for both repair and recombination, since an interaction-defective rad1 allele phenocopies the null [PMID:1518857, PMID:1620114]. Genetically, Rad1-Rad10 is specifically required to remove nonhomologous 3' tails during single-strand annealing and gene-conversion DSB repair [PMID:1411547, PMID:7891718], to process 3'-blocked termini such as 3'-phosphoglycolate from oxidative breaks [PMID:15371342], and to repair Top1 cleavage complexes, with the catalytic-dead rad1-D869A mutant confirming the endonuclease requirement [PMID:12368472]; targeting to lesions and substrates is provided by accessory factors including Rad14 in NER and Saw1 in SSA [PMID:16428464, PMID:23299942]. In a second capacity, Rad1 is a subunit of the heterotrimeric 9-1-1 (Rad9-Hus1-Rad1) PCNA-like sliding clamp [PMID:11340080], whose toroidal ring architecture was confirmed crystallographically [PMID:19446481]. Rad1 is essential for 9-1-1 integrity and for ATR-dependent (not ATM-dependent) Chk1 activation, with its loss destabilizing Rad9 and Hus1, causing radioresistant DNA synthesis and chromosomal abnormalities [PMID:15184880]. The clamp is loaded onto damaged chromatin by Rad17 in a proximal, kinase-independent step [PMID:20110345, PMID:12228248] and activates Chk1 by positioning TopBP1's activation domain, recruited via CK2-phosphorylated Rad9, to stimulate ATR [PMID:17575048, PMID:20545769]. Beyond signaling, 9-1-1 acts as a damage-specific scaffold that stimulates base excision repair enzymes including Pol β, FEN1, DNA ligase I, APE1, NEIL1, TDG and MYH through a repair-enzyme-binding site on the Rad1 IDC loop that is competitively blocked by p21 [PMID:19446481, PMID:19535328, PMID:15556996, PMID:16879101]. The complex also localizes to telomeres and positively regulates telomerase [PMID:16890531], and contributes to meiotic chromosome surveillance [PMID:23468651, PMID:9716408].","teleology":[{"year":1992,"claim":"Established that Rad1 and Rad10 form an obligate, salt-resistant complex and that this physical association is itself required for repair and recombination, defining Rad1's first functional context.","evidence":"Reciprocal Co-IP in vivo and in vitro plus an interaction-defective rad1 allele in yeast, with C-terminal domain mapping by truncation","pmids":["1518857","1620114"],"confidence":"High","gaps":["Did not establish which subunit carries catalytic activity","Did not define substrate specificity of the complex"]},{"year":1992,"claim":"Placed Rad1 genetically at the 3'-end processing step of recombination, showing it removes nonhomologous tails during DSB repair.","evidence":"Genetic epistasis with HO-induced DSBs and Southern blot of recombination products in rad1 yeast","pmids":["1411547"],"confidence":"High","gaps":["Biochemical mechanism of tail removal not yet demonstrated","Did not distinguish NER from recombination roles"]},{"year":1994,"claim":"Provided the biochemical basis for Rad1's repair and recombination roles by showing the complex cleaves at duplex–single-strand junctions on the 3'-tailed strand and produces clean termini, unifying the NER incision and tail-removal functions.","evidence":"In vitro cleavage of model recombination/repair intermediates and termini analysis with purified Rad1-Rad10","pmids":["8091230","8253764","8479526"],"confidence":"High","gaps":["Catalytic subunit identity still ambiguous","In vivo lesion-targeting mechanism unaddressed"]},{"year":1995,"claim":"Reconstituted the NER dual incision step, demonstrating Rad1-Rad10 performs the 5' incision and cooperates with XPG, and reported failure to detect Holliday junction binding, conflicting with an earlier catalytic-subunit claim.","evidence":"In vitro bubble-substrate incision assay with purified Rad1-Rad10 and XPG; negative Holliday junction binding assay","pmids":["7559571","7935767"],"confidence":"High","gaps":["Conflicting reports on Rad1-only Holliday junction activity unresolved","Substrate selection rules among related nucleases not yet defined"]},{"year":1995,"claim":"Showed the recombination role is specific to Rad1-Rad10 among NER factors, separating this sub-pathway from canonical NER.","evidence":"Genetic analysis of HO-induced DSB repair across multiple NER deletion strains with physical monitoring","pmids":["7891718"],"confidence":"High","gaps":["Factors targeting the nuclease to recombination intermediates unknown"]},{"year":1998,"claim":"Identified human HRAD1 as the functional ortholog of fission yeast rad1+ with intrinsic nuclease activity and a checkpoint role, bridging yeast biochemistry to the mammalian checkpoint.","evidence":"Complementation of S. pombe rad1 mutants; recombinant 3'→5' exonuclease assay; nuclear localization and meiotic chromosome staining","pmids":["9716408","9660799"],"confidence":"Medium","gaps":["Exonuclease activity from bacterial protein not validated in human cell context","Relationship of human nuclease activity to the 9-1-1 clamp role unclear"]},{"year":2001,"claim":"Defined Rad1's second context as a stable heterotrimeric 9-1-1 clamp and mapped intersubunit contacts, establishing the structural framework for checkpoint and BER functions.","evidence":"Reconstitution by co-expression, differential-tag Co-IP, size-exclusion chromatography of the human Rad9-Hus1-Rad1 complex","pmids":["11340080","10359610","9872989"],"confidence":"High","gaps":["How the ring is loaded onto DNA not yet established","Functional output of the complex undefined at this stage"]},{"year":2002,"claim":"Showed 9-1-1 chromatin loading is a proximal, kinase- and replication-independent event, positioning the clamp upstream in the checkpoint cascade.","evidence":"Chromatin fractionation with kinase inhibitors and phospho-site mutants in human cells","pmids":["12228248"],"confidence":"Medium","gaps":["Loading machinery not identified in this study","Direct DNA recognition determinants unaddressed"]},{"year":2004,"claim":"Established Rad1 as essential for 9-1-1 integrity and ATR-dependent (not ATM-dependent) Chk1 signaling, linking the clamp to genome stability phenotypes.","evidence":"siRNA knockdown of RAD1 with complex-stability blots, Chk1 phosphorylation, DNA fiber, and cytogenetic assays","pmids":["15184880"],"confidence":"High","gaps":["Molecular intermediary between 9-1-1 and ATR not yet defined here","Distinct contributions of clamp vs nuclease roles to phenotypes not separated"]},{"year":2004,"claim":"Revealed a scaffolding function for 9-1-1 in base excision repair by showing it binds and stimulates specific BER enzymes (Pol β, FEN1) distinct from PCNA, broadening Rad1's role beyond signaling.","evidence":"In vitro pull-down and enzyme stimulation assays with purified 9-1-1 against multiple polymerases and substrates","pmids":["15314187","15556996"],"confidence":"Medium","gaps":["Enzyme-binding surface on the clamp not yet localized","In vivo relevance of stimulation not directly tested"]},{"year":2007,"claim":"Defined the mechanism of 9-1-1-driven Chk1 activation: the clamp localizes TopBP1's activation domain via phospho-Rad9 to stimulate ATR, with this requirement bypassed by tethering the AD to other chromatin anchors.","evidence":"Co-IP, TopBP1-PCNA/H2B fusion bypass experiments, and phospho-Ser373 mutagenesis in human cells and Xenopus extracts","pmids":["17575048","17636252"],"confidence":"High","gaps":["Kinase responsible for the activating Rad9 phosphorylation not identified here","Spatial coordination with the loader unresolved"]},{"year":2007,"claim":"Extended the BER scaffold role of 9-1-1 across multiple glycosylases and the AP-endonuclease/long-patch BER pathway, with several enzymes binding through the Rad1/Hus1 subunits.","evidence":"Co-IP, in vitro glycosylase/endonuclease stimulation, and LP-BER reconstitution for NEIL1, TDG, MYH and APE1","pmids":["17395641","17855402","16879101","17426133"],"confidence":"Medium","gaps":["Whether all interactions occur simultaneously or competitively unresolved","In vivo BER contribution of clamp not quantified"]},{"year":2009,"claim":"Provided the crystallographic basis for damage-specific 9-1-1 function, locating the repair-enzyme-binding site on the Rad1 IDC loop and showing it is competed by p21, while the Rad9 tail regulates DNA binding.","evidence":"X-ray structures of human Rad9-Hus1-Rad1 with FEN1 PIP-box co-crystallization, p21 competition, and truncation DNA-binding assays","pmids":["19446481","19535328","19464297"],"confidence":"High","gaps":["Structure of DNA-loaded clamp not resolved","Conformational basis of loader engagement not fully defined"]},{"year":2010,"claim":"Placed Rad17 mechanistically upstream of 9-1-1, showing ATP-dependent loading and CK2 phosphorylation of Rad9 are prerequisites for TopBP1 recruitment and checkpoint activation.","evidence":"Xenopus extract biochemistry with Rad17 ATPase mutants and chromatin fractionation; in vitro CK2 kinase assays with phospho-site mutants and UV/MMS sensitivity","pmids":["20110345","20545769"],"confidence":"High","gaps":["Precise order of loading versus TopBP1 binding events partially inferred","Mammalian in vivo loading kinetics not directly measured"]},{"year":2013,"claim":"Identified accessory targeting factors and an alternative meiotic role for Rad1, showing Saw1 directs Rad1-Rad10 to 3'-tailed SSA substrates and that meiotic Rad1 localization can be 9-1-1-independent.","evidence":"Reconstituted cleavage with purified Rad1/Rad10 and Saw1, ChIP, and Co-IP; conditional Hus1 knockout mouse meiotic immunofluorescence","pmids":["23299942","18471978","23468651"],"confidence":"High","gaps":["Molecular nature of 9-1-1-independent Rad1 meiotic function undefined","Whether human Rad1 uses a Saw1-like targeting factor unknown"]},{"year":null,"claim":"How the nuclease (Rad1-Rad10) and checkpoint-clamp (9-1-1) identities of Rad1 are coordinated within a single proteome, and the structural basis of conflicting Holliday-junction observations, remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No study reconciles the dual structural assemblies of Rad1 in one system","Conflicting Holliday junction binding reports unresolved","In vivo separation of clamp vs nuclease contributions to mammalian phenotypes incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140097","term_label":"catalytic activity, acting on DNA","supporting_discovery_ids":[0,1,2,4,37,38,44]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,2,4,38,47]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[3,16]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[12,14,15,25,31]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[24,25,26,28,29,30,31]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[12,13,14]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[7,11,48]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[22,43,50]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[46,48,50]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[2,4,25,31,38,39]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[18,21,23]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[18,20,22,23]}],"complexes":["9-1-1 (Rad9-Hus1-Rad1) clamp","Rad1-Rad10 endonuclease"],"partners":["RAD10","RAD9","HUS1","RAD17","TOPBP1","FEN1","RAD14","SAW1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O60671","full_name":"Cell cycle checkpoint protein RAD1","aliases":["Rad1-like DNA damage checkpoint protein"],"length_aa":282,"mass_kda":31.8,"function":"Component of the 9-1-1 cell-cycle checkpoint response complex that plays a major role in DNA repair (PubMed:10846170, PubMed:10884395). The 9-1-1 complex is recruited to DNA lesion upon damage by the RAD17-replication factor C (RFC) clamp loader complex (PubMed:12578958). Acts then as a sliding clamp platform on DNA for several proteins involved in long-patch base excision repair (LP-BER) (PubMed:15871698). The 9-1-1 complex stimulates DNA polymerase beta (POLB) activity by increasing its affinity for the 3'-OH end of the primer-template and stabilizes POLB to those sites where LP-BER proceeds; endonuclease FEN1 cleavage activity on substrates with double, nick, or gap flaps of distinct sequences and lengths; and DNA ligase I (LIG1) on long-patch base excision repair substrates (PubMed:15314187, PubMed:15556996, PubMed:15871698). The 9-1-1 complex is necessary for the recruitment of RHNO1 to sites of double-stranded breaks (DSB) occurring during the S phase (PubMed:21659603)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/O60671/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/RAD1","classification":"Common Essential","n_dependent_lines":665,"n_total_lines":1208,"dependency_fraction":0.5504966887417219},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"HUS1","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/search/RAD1","total_profiled":1310},"omim":[{"mim_id":"614508","title":"MIRROR MOVEMENTS 2; MRMV2","url":"https://www.omim.org/entry/614508"},{"mim_id":"614085","title":"RAD9-, RAD1-, AND HUS1-INTERACTING NUCLEAR ORPHAN 1; RHNO1","url":"https://www.omim.org/entry/614085"},{"mim_id":"611153","title":"XPA, DNA DAMAGE RECOGNITION AND REPAIR FACTOR; XPA","url":"https://www.omim.org/entry/611153"},{"mim_id":"609713","title":"HUS1 CHECKPOINT CLAMP COMPONENT B; HUS1B","url":"https://www.omim.org/entry/609713"},{"mim_id":"608368","title":"RAD9 CHECKPOINT CLAMP COMPONENT B; RAD9B","url":"https://www.omim.org/entry/608368"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RAD1"},"hgnc":{"alias_symbol":["HRAD1","REC1"],"prev_symbol":[]},"alphafold":{"accession":"O60671","domains":[{"cath_id":"3.70.10.10","chopping":"2-136","consensus_level":"high","plddt":90.1053,"start":2,"end":136},{"cath_id":"3.70.10.10","chopping":"151-270","consensus_level":"high","plddt":92.0188,"start":151,"end":270}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O60671","model_url":"https://alphafold.ebi.ac.uk/files/AF-O60671-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O60671-F1-predicted_aligned_error_v6.png","plddt_mean":89.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RAD1","jax_strain_url":"https://www.jax.org/strain/search?query=RAD1"},"sequence":{"accession":"O60671","fasta_url":"https://rest.uniprot.org/uniprotkb/O60671.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O60671/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O60671"}},"corpus_meta":[{"pmid":"17575048","id":"PMC_17575048","title":"The 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this activity is presumed to remove non-homologous regions during mitotic recombination and to incise damaged DNA during nucleotide excision repair.\",\n      \"method\": \"In vitro biochemical assay with purified proteins; single-stranded DNA endonuclease activity reconstituted from purified Rad1 and Rad10\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro endonuclease activity with purified proteins, replicated in multiple subsequent studies\",\n      \"pmids\": [\"8479526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Purified yeast Rad1-Rad10 endonuclease activity on single-stranded and double-stranded DNA produces 3'-hydroxyl and 5'-phosphate termini; activity on double-stranded DNA is strongly dependent on negative superhelicity.\",\n      \"method\": \"In vitro biochemical characterization with purified Rad1 and Rad10 proteins; agarose gel electrophoresis and TCA precipitation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — purified proteins, multiple substrates and orthogonal biochemical methods in a single rigorous study\",\n      \"pmids\": [\"8253764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Rad1-Rad10 complex cleaves model recombination/repair intermediates specifically at duplex-single-strand junctions, acting only on the strand containing the 3' single-stranded tail; this defines the biochemical basis for its role in removing nonhomologous tails during recombination and for 5' incision during NER.\",\n      \"method\": \"In vitro cleavage assay using model recombination and repair intermediate substrates with purified Rad1-Rad10\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with defined substrates, supported by genetic evidence in same paper\",\n      \"pmids\": [\"8091230\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Yeast Rad1 protein binds specifically to Holliday junctions and, in the presence of magnesium, catalyzes endonucleolytic cleavage of the junction independently of Rad10, identifying Rad1 as the catalytic subunit of the Rad1/Rad10 endonuclease.\",\n      \"method\": \"In vitro binding and cleavage assay with purified Rad1 protein and synthetic Holliday junction substrates\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — single lab in vitro assay; note that another paper (PMID:7559571) using independently purified proteins failed to reproduce Holliday junction interaction, reducing confidence\",\n      \"pmids\": [\"7935767\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Purified Rad1-Rad10 complex incises a synthetic bubble DNA substrate at the 5'-side of the centrally unpaired region; when combined with XPG, dual incisions at both ends of the bubble are observed, reconstituting the dual incision step of nucleotide excision repair in vitro. Separately, Rad1 failed to show interaction with synthetic Holliday junctions in this study (negative result).\",\n      \"method\": \"In vitro incision assay with purified Rad1-Rad10 and XPG on bubble DNA substrates; synthetic Holliday junction binding assay (negative)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — dual incision reconstituted with purified proteins; independently replicated the NER incision mechanism\",\n      \"pmids\": [\"7559571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Yeast Rad1 and Rad10 proteins form a stable, specific complex in vitro and in vivo; the interaction is resistant to 1 M NaCl and low SDS; a rad1 mutant allele encoding a protein that fails to bind Rad10 is as defective in DNA repair and recombination as a null mutant, demonstrating that complex formation is essential for both biological activities.\",\n      \"method\": \"Co-immunoprecipitation from yeast cell extracts; in vitro co-translation and co-immunoprecipitation; mutational analysis (interaction-defective rad1 allele)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — reciprocal Co-IP in vivo and in vitro, plus loss-of-interaction mutant with matching loss-of-function phenotype; replicated by multiple labs\",\n      \"pmids\": [\"1518857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Stable and specific in vitro interaction between Rad1 and Rad10 proteins was mapped: the Rad10-binding domain of Rad1 maps to the C-terminal region, and the Rad1-binding domain of Rad10 also maps to its C-terminal region; these domains are evolutionarily conserved and hydrophobic.\",\n      \"method\": \"In vitro co-immunoprecipitation with in vitro translated proteins; domain mapping by truncation analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro domain mapping with multiple truncations, replicated across labs\",\n      \"pmids\": [\"1620114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Rad1 and Rad10 form a constitutive complex in the cell nucleus; the Rad10-binding domain of Rad1 maps to amino acids 809–997, and the Rad1-binding domain of Rad10 maps to amino acids 90–210; these domains are hydrophobic and evolutionarily conserved.\",\n      \"method\": \"Yeast two-hybrid assay; domain mapping with truncation constructs\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — two-hybrid interaction mapping, consistent with in vitro biochemical data from other labs\",\n      \"pmids\": [\"8361362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"In Saccharomyces cerevisiae, Rad1 is required to remove nonhomologous DNA sequences (~60 bp) from the 3' ends of recombining DNA during double-strand break repair; recombination is restored when the ends are made homologous, placing Rad1 in the 3'-end processing step during single-strand annealing and gene conversion.\",\n      \"method\": \"Genetic epistasis using HO endonuclease-induced DSBs in rad1 mutant yeast; Southern blot analysis of recombination products\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean loss-of-function with specific molecular readout, foundational genetic study replicated extensively\",\n      \"pmids\": [\"1411547\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Among nucleotide excision repair genes, only RAD1 and RAD10 (not RAD2, RAD3, RAD14, RAD7, or RAD16) are required for removing nonhomologous sequences from DSB ends during gap repair and single-strand annealing, demonstrating a specific role for Rad1-Rad10 in this recombination sub-pathway.\",\n      \"method\": \"Genetic analysis of HO-induced DSB repair in multiple NER gene deletion strains; physical monitoring by Southern blot\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic genetic epistasis with multiple mutant combinations, replicated across labs\",\n      \"pmids\": [\"7891718\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Human hRad1 and hHus1 associate in a complex that interacts with a highly modified (phosphorylated) form of hRad9; hHus1 and hRad1 do not associate with hRad17; hRad9 is phosphorylated in response to DNA damage.\",\n      \"method\": \"Co-immunoprecipitation from human cell extracts; Western blotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP from human cells showing complex formation; single lab but consistent with yeast data\",\n      \"pmids\": [\"9872989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Human hRAD9 physically associates with hRAD1 and hHUS1; hRAD1 and hHUS1 also interact with each other; hRAD9 is a nuclear phosphoprotein present in multiple phosphorylation forms in vivo.\",\n      \"method\": \"Co-immunoprecipitation from human cells; nuclear fractionation; Western blot\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP, nuclear fractionation, single lab; confirmed by independent labs\",\n      \"pmids\": [\"10359610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The human hRad9-hHus1-hRad1 (9-1-1) complex is a stable, discrete heterotrimeric complex of ~160 kDa in which: the N-terminus of hRad9 interacts with hRad1, the N-terminus of hRad1 interacts with hHus1, and the N-terminus of hHus1 interacts with the C-terminus of hRad9's PCNA-like region; approximately half the cellular hRad1 participates in this complex.\",\n      \"method\": \"Biochemical fractionation; reconstitution by co-expression in heterologous system; co-immunoprecipitation with differentially tagged proteins; size-exclusion chromatography\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — complex reconstituted in heterologous system, reciprocal Co-IP with domain mapping, multiple orthogonal methods\",\n      \"pmids\": [\"11340080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Computational structure prediction indicates that human Rad1 (and its yeast/fission yeast orthologs) shares a PCNA-like fold; the three proteins Rad9, Hus1, and Rad1 are predicted to form a heterotrimeric PCNA-like ring, with a defined order within the ring and identified contact regions between subunits.\",\n      \"method\": \"Computational fold recognition, comparative modeling, and generalized sequence profiles; structural prediction validated against existing biochemical data\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Moderate — computational prediction only; later confirmed experimentally by crystal structures\",\n      \"pmids\": [\"10871397\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Crystal structure of the human 9-1-1 (Rad9-Hus1-Rad1) complex reveals a toroidal PCNA-like heterotrimeric ring; the structure shows significant differences among the three subunits at sites implicated in clamp loader binding and ligand binding; biochemical analysis identifies a single repair enzyme-binding site on 9-1-1 that is competitively blocked by p21(cip1/waf1).\",\n      \"method\": \"X-ray crystallography; biochemical competition assay with p21\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional biochemical validation; independently confirmed by two other crystal structures published the same year\",\n      \"pmids\": [\"19446481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Crystal structure of the human Rad9(1-272)-Hus1-Rad1 complex at 2.5 Å resolution confirms the closed toroidal architecture; co-crystallization reveals that an FEN1 PIP-box peptide binds to the interdomain connecting loop (IDC loop) of hRad1, providing the molecular basis for damage repair-specific activity of 9-1-1 distinct from PCNA.\",\n      \"method\": \"X-ray crystallography at 2.5 Å; co-crystallization with FEN1 PIP-box peptide; biochemical assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with co-crystal validation of FEN1 binding site on Rad1 IDC loop\",\n      \"pmids\": [\"19535328\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Crystal structure of human Rad9(1-272)-Hus1-Rad1 at 2.5 Å resolution shows the 9-1-1 complex forms a closed ring; the full-length 9-1-1 complex (with Rad9 C-terminal tail) does not form a stable complex with 5' recessed DNA, but the Rad9(1-272) truncation does, indicating that the C-terminal tail of Rad9 regulates DNA binding by 9-1-1.\",\n      \"method\": \"X-ray crystallography; DNA-binding assay comparing full-length and truncated 9-1-1\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with functional DNA binding validation; single lab but two orthogonal methods\",\n      \"pmids\": [\"19464297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Human hRad17 interacts with the PCNA-like checkpoint proteins hRad1, hRad9, and hHus1 in a manner resembling the RFC–PCNA clamp loader interaction; DNA damage affects the association of hRad17 with the clamp-like proteins; mutational analysis of hRad1 and hRad17 confirms properties similar to RFC–PCNA interaction.\",\n      \"method\": \"Co-immunoprecipitation from human cells; mutational analysis of interaction surfaces; Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP with mutational validation, single lab but multiple constructs\",\n      \"pmids\": [\"10884395\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The 9-1-1 complex activates Chk1 via binding of Rad9's C-terminal tail to TopBP1, which then stimulates ATR-mediated Chk1 phosphorylation through TopBP1's activation domain (AD); fusion of the AD to PCNA or histone H2B bypasses the requirement for the 9-1-1 clamp, demonstrating that the primary role of 9-1-1 in Chk1 activation is to localize TopBP1's AD to stalled replication forks.\",\n      \"method\": \"Co-immunoprecipitation; TopBP1-PCNA and TopBP1-H2B fusion bypass experiments in human cells; Chk1 phosphorylation assays\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — epistasis via bypass fusion constructs plus Co-IP; replicated by independent lab (PMID:17636252)\",\n      \"pmids\": [\"17575048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The 9-1-1 complex regulates the interaction of TopBP1 with ATR-ATRIP in Xenopus egg extracts; the BRCT I-II region of TopBP1 binds specifically to the 9-1-1 complex via the C-terminal domain of Rad9, and this interaction requires phosphorylation of Rad9 Ser-373; mutation of TopBP1 BRCT I-II or Rad9 Ser-373→Ala causes checkpoint defects.\",\n      \"method\": \"Co-immunoprecipitation from Xenopus egg extracts; checkpoint assays with mutant proteins; phospho-specific analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Xenopus biochemical reconstitution with phospho-site mutagenesis, functional checkpoint validation; independent replication of 9-1-1/TopBP1 interaction\",\n      \"pmids\": [\"17636252\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Casein kinase 2 (CK2) phosphorylates Ser-341 and Ser-387 in the C-terminal tail of human Rad9; phosphorylation at these sites (particularly Ser-387) is required for the 9-1-1 complex to physically interact with TopBP1 and for efficient ATR-dependent checkpoint activation; cells expressing phospho-deficient Rad9 (S341A/S387A) are hypersensitive to UV and MMS.\",\n      \"method\": \"In vitro kinase assay with purified CK2 and 9-1-1; Co-IP; mutagenesis; UV/MMS sensitivity assays\",\n      \"journal\": \"Genes to cells : devoted to molecular & cellular mechanisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro kinase assay plus Co-IP plus functional complementation, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"20545769\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Rad17 mediates the interaction between 9-1-1 and TopBP1 in Xenopus egg extracts; ATP binding to Rad17 is essential for 9-1-1–TopBP1 association, and ATP hydrolysis by Rad17 is required for 9-1-1 loading onto DNA and for elevated TopBP1 chromatin accumulation; a 9-1-1 mutant unable to bind TopBP1 still promotes normal TopBP1 chromatin accumulation, placing Rad17 upstream.\",\n      \"method\": \"Xenopus egg extract biochemistry; Rad17 ATPase mutants; 9-1-1 TopBP1-binding mutant; chromatin fractionation assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple Xenopus mutant combinations establishing mechanism; single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"20110345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Genotoxin-induced chromatin association of the 9-1-1 complex does not require ATM, ATR, or DNA-PK catalytic activity, does not require Rad9 Ser-272 phosphorylation, and does not require DNA replication, establishing that 9-1-1 chromatin loading is a proximal, kinase-independent event in the checkpoint cascade.\",\n      \"method\": \"Chromatin fractionation assay in human cells with pharmacological kinase inhibitors and phospho-site mutants; flow cytometry\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple inhibitor conditions and mutants; single lab\",\n      \"pmids\": [\"12228248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Loss of RAD1 in mammalian cells destabilizes Rad9 and Hus1, causing disintegration of the 9-1-1 complex; Rad1 depletion impairs ATR-dependent (but not ATM-dependent) Chk1 activation, causes radioresistant DNA synthesis (RDS), and results in chromosomal abnormalities, establishing Rad1 as essential for ATR-dependent checkpoint signaling.\",\n      \"method\": \"siRNA knockdown of RAD1; Western blot for complex stability; Chk1 phosphorylation assays; DNA fiber assays; cytogenetics\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KD with multiple orthogonal functional readouts; single lab\",\n      \"pmids\": [\"15184880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The human 9-1-1 complex physically interacts with DNA polymerase beta (Pol β) in vitro, stimulates its activity by increasing its affinity for the primer-template, and enhances strand displacement synthesis; 9-1-1 does not stimulate DNA polymerase lambda, alpha, or delta.\",\n      \"method\": \"In vitro pull-down; DNA polymerase activity assays with and without 9-1-1; primer extension assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro reconstitution with specificity controls; single lab\",\n      \"pmids\": [\"15314187\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The human 9-1-1 complex binds and stimulates flap endonuclease 1 (FEN1) on flap, nick, and gapped substrates; stimulation requires 9-1-1 entry to the double-stranded region; 9-1-1 does not substitute for PCNA in stimulating DNA polymerase beta, making it a damage-specific FEN1 activator.\",\n      \"method\": \"In vitro FEN1 activity assay with purified 9-1-1; cleavage assays on multiple substrates\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified proteins, multiple substrates, specificity controls; replicated by additional labs\",\n      \"pmids\": [\"15556996\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The human 9-1-1 complex interacts with and stimulates DNA ligase I; 9-1-1 improves the binding of DNA ligase I to nicked double-stranded DNA; UV irradiation stimulates 9-1-1–ligase I complex formation in cells; stimulation is specific for ligase I and does not require encirclement of the DNA substrate (unlike PCNA).\",\n      \"method\": \"Co-immunoprecipitation from human cells; in vitro ligation assay; UV irradiation stimulation experiment\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP from cells plus in vitro functional assay; single lab\",\n      \"pmids\": [\"15871698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The 9-1-1 complex stimulates DNA ligase I by improving its binding to nicked DNA; high concentrations of casein kinase II inhibit ligase I but do not prevent 9-1-1-mediated stimulation; unlike PCNA, 9-1-1 stimulates DNA ligase I equally on linear and circular substrates, indicating encirclement is not required.\",\n      \"method\": \"In vitro ligation assay; DNA binding assay; kinase inhibition experiment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mechanistic comparisons; single lab\",\n      \"pmids\": [\"16731526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Human MYH DNA glycosylase interacts with hRad1 and hHus1 (but not hRad9) of the 9-1-1 complex; the major interaction site maps to residues 295–350 of hMYH; hHus1 and the 9-1-1 complex enhance MYH glycosylase activity; the hMYH-hHus1 interaction is enhanced after ionizing radiation.\",\n      \"method\": \"Co-immunoprecipitation; in vitro pulldown; glycosylase activity assay with and without 9-1-1; mutagenesis of interaction sites\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus in vitro functional assay plus mutagenesis; single lab\",\n      \"pmids\": [\"16879101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The human 9-1-1 complex interacts with hNEIL1 DNA glycosylase; residues 290–350 of hNEIL1 are important for 9-1-1 association; hHus1, hRad1, and hRad9 individually and as a complex significantly stimulate hNEIL1 glycosylase activity; a fraction of hNEIL1 nuclear foci co-localizes with hRad9 foci after hydrogen peroxide treatment.\",\n      \"method\": \"Co-immunoprecipitation; in vitro glycosylase stimulation assay; immunofluorescence co-localization\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus in vitro activity assay plus localization; single lab, three orthogonal methods\",\n      \"pmids\": [\"17395641\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The human 9-1-1 complex interacts with thymine DNA glycosylase (hTDG); hHus1 interacting domain maps to residues 67–110 of hTDG (Val74 critical); hHus1, hRad1, hRad9 individually and as a complex stimulate hTDG glycosylase activity; the hRad9-hTDG interaction is enhanced after MNNG treatment.\",\n      \"method\": \"Co-immunoprecipitation; mutagenesis; in vitro glycosylase activity assay; immunofluorescence\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with mutagenesis plus in vitro functional assay; single lab\",\n      \"pmids\": [\"17855402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The 9-1-1 complex interacts with APE1 in vitro and in vivo, stimulates APE1 AP-endonuclease activity, and stimulates long-patch base excision repair (LP-BER) reconstituted in vitro by specifically enhancing the activities of APE1 and Pol β as early LP-BER components.\",\n      \"method\": \"Co-immunoprecipitation; in vitro AP-endonuclease assay; LP-BER reconstitution assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro reconstitution with multiple substrates plus Co-IP; single lab\",\n      \"pmids\": [\"17426133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The 9-1-1 complex independently binds and activates FEN1, and this stimulation is abolished by acetylation of FEN1 by p300-HAT, whereas PCNA stimulation of FEN1 is unaffected by acetylation, suggesting independent regulatory mechanisms for the two clamps.\",\n      \"method\": \"In vitro FEN1 activity assay; p300-mediated acetylation of FEN1; comparison with PCNA stimulation\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with post-translational modification comparison; single lab\",\n      \"pmids\": [\"16216273\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The 9-1-1 complex directly interacts with RPA in human cells; this interaction is mediated by Rad9 binding to RPA70 and RPA32 subunits; UV or camptothecin treatment stimulates 9-1-1–RPA interaction; RPA knockdown by siRNA blocks damage-dependent chromatin association of 9-1-1 and also inhibits 9-1-1 complex formation.\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown; immunofluorescence co-localization; chromatin fractionation\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus functional siRNA experiment; single lab\",\n      \"pmids\": [\"15897895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"In Schizosaccharomyces pombe, Hus1 associates in a complex with Rad9 and Rad1; this Rad1-Rad9-Hus1 complex is detectable in soluble extracts; nuclear localization of Hus1 depends on Rad17; Rad17 forms a separate complex in soluble extracts distinct from the Rad1-Rad9-Hus1 complex but shows transient interaction with Rad1.\",\n      \"method\": \"Immunoprecipitation from S. pombe extracts; indirect immunofluorescence; two-hybrid assay; in vitro association\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — multiple methods including IP, immunofluorescence, two-hybrid; single lab\",\n      \"pmids\": [\"10648611\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Mismatch repair genes MSH2 and MSH3 function in the RAD1-RAD10 recombination pathway in yeast; msh3Δ has an effect similar to rad1Δ and rad10Δ on recombination between his3 duplications and homologous integration; epistasis analysis places MSH2 and MSH3 in the RAD1-RAD10 pathway.\",\n      \"method\": \"Genetic epistasis analysis; recombination frequency measurement in single and double mutants\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis with multiple mutant combinations; single lab\",\n      \"pmids\": [\"8849883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Yeast Rad1 (with Mre11 and Rad50) defines a Ku-independent microhomology-mediated end joining (MMEJ) pathway for repairing DSBs lacking complementary end sequences; this MMEJ produces deletions annealed by ~8–10 bp microhomology at junctions and is Ku-independent but strongly dependent on Mre11, Rad50, and Rad1.\",\n      \"method\": \"Genetic analysis with HO-induced DSBs in yku70Δ rad1Δ and mre11Δ mutants; Southern blot analysis of repair products\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with defined molecular readout; single lab\",\n      \"pmids\": [\"14612421\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The yeast Rad1-Rad10 structure-specific endonuclease and tyrosyl-DNA phosphodiesterase Tdp1 function as primary redundant pathways for repairing Top1 replicative damage (Top1 cleavage complexes); the catalytic point mutant rad1-D869A (Rad1-Rad10 nuclease-dead) is as sensitive as rad1Δ, confirming endonuclease activity is required; the Rad1-Rad10 pathway depends on RAD52, RAD51, RAD50, RAD59, and SRS2 but is independent of other NER genes.\",\n      \"method\": \"Genetic analysis with camptothecin sensitivity; use of catalytic point mutant rad1-D869A; epistasis with multiple recombination genes\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — catalytic point mutant establishes endonuclease requirement; extensive epistasis mapping; confirmed by multiple genetic interactions\",\n      \"pmids\": [\"12368472\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Yeast Rad1-Rad10 nuclease is required for removing 3'-blocked termini (including 3'-phosphoglycolate) from DNA strand breaks induced by H2O2; Rad1-Rad10 in vitro efficiently cleaves DNA modified with a 3'-phosphoglycolate terminus; the nuclease acts redundantly with Apn1 and Apn2 in this 3'-end processing pathway.\",\n      \"method\": \"In vitro cleavage assay with 3'-phosphoglycolate-modified substrates; genetic analysis (apn1 apn2 rad1 triple mutants); H2O2 sensitivity experiments\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro cleavage of modified substrate plus genetic validation; single lab with two orthogonal approaches\",\n      \"pmids\": [\"15371342\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Complex formation between Rad1-Rad10 nuclease and the damage recognition protein Rad14 is essential for Rad1-Rad10 to function in NER in vivo; two rad1 mutations were identified that render cells as UV-sensitive as rad1Δ but do not affect Rad1's recombination function, and these mutations abolish Rad14 interaction without affecting Rad10 interaction, establishing that Rad14 binding provides damage-site targeting for Rad1-Rad10.\",\n      \"method\": \"Mutational analysis of RAD1; in vivo UV sensitivity; biochemical complex formation assays; separation-of-function mutants\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — separation-of-function mutations with biochemical and genetic validation; single lab with two orthogonal methods\",\n      \"pmids\": [\"16428464\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Saw1 (Yal027Wp) is required for Rad1/Rad10-dependent 3' flap cleavage during single-strand annealing (SSA); Saw1 physically interacts with Rad1/Rad10, Msh2/Msh3, and Rad52; Saw1 mutants that fail to interact with Rad1 but retain Rad52/Msh2 interaction are specifically defective in 3' flap removal; deletion of SAW1 abolishes association of Rad1 at SSA intermediates in vivo.\",\n      \"method\": \"Microarray-based genetic screen; Co-IP; physical interaction mapping; chromatin immunoprecipitation (ChIP); SSA assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (genetic screen, Co-IP, ChIP, separation-of-function mutants); replicated in follow-up study\",\n      \"pmids\": [\"18471978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Mec1/Tel1-dependent phosphorylation of Slx4 at Thr113 is required for efficient cleavage of 3' non-homologous DNA tails by Rad1-Rad10 during single-strand annealing and homologous recombination; Slx4 is recruited to 3' NH tails during DSB repair independently of its phosphorylation; deletion of both MEC1 and TEL1 severely reduces NH tail cleavage.\",\n      \"method\": \"Genetic analysis; site-directed mutagenesis of Slx4 phosphorylation sites; ChIP; SSA assay\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-site mutagenesis with functional readout; single lab\",\n      \"pmids\": [\"20382573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Saw1 is a structure-specific DNA binding protein with high affinity for splayed arm and 3'-flap DNAs; Saw1 physically interacts with Rad1 and facilitates targeting of Rad1 to 3'-tailed substrates in vivo and in vitro; Saw1 enhances 3'-tail cleavage by Rad1/Rad10 in a purified reconstituted system.\",\n      \"method\": \"In vitro DNA binding assay; in vitro cleavage assay with purified Rad1/Rad10 and Saw1; ChIP; Co-IP\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro reconstitution with purified proteins plus in vivo validation; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"23299942\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"In fission yeast, damage-induced Crb2 (Rad9/53BP1 homolog) nuclear foci form independently of Rad1, Rad3, and Rad17 complexes, but these complexes are required for persistent (long-lasting) retention of Crb2 at DSB sites, placing the 9-1-1/Rad3 complexes in the retention rather than initial recruitment of Crb2.\",\n      \"method\": \"Live-cell fluorescence microscopy of Crb2-GFP in rad1, rad3, rad17 mutants; time-course analysis of foci persistence\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional interpretation; single lab\",\n      \"pmids\": [\"12917337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Mus81-Mms4 and Rad1-Rad10 are homologous structure-specific endonucleases with distinct cleavage site selection: Rad1-Rad10 cleavage site is determined by the branch point, while Mus81-Mms4 cleavage is determined by the 5' end of the strand at the flap junction; substrates lacking a 5' end near the flap are cleaved poorly by Mus81-Mms4 but well by Rad1-Rad10.\",\n      \"method\": \"In vitro cleavage assay with defined substrates comparing Mus81-Mms4 and Rad1-Rad10 endonucleases\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — comparative in vitro biochemistry with defined substrates; single lab\",\n      \"pmids\": [\"12724407\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The Rad1-Rad10 nuclease promotes crossover and non-crossover recombinants between ectopic sequences; crossover products are absent only from the mus81Δ rad1Δ yen1Δ triple mutant, indicating that Rad1-Rad10 participates with Mus81-Mms4 and Yen1 in processing recombination intermediates between dispersed repeats; Rad1-dependent joint molecules accumulate in mus81Δ yen1Δ mutants.\",\n      \"method\": \"Genetic analysis; physical monitoring of recombination intermediates by Southern blot; triple mutant analysis\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — physical monitoring of intermediates plus genetic epistasis; single lab\",\n      \"pmids\": [\"22885325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In mouse testis, HUS1 loss (in 9-1-1) causes persistent meiotic DSBs, synapsis defects, and spermatocyte depletion; RAD9 localizes to RAD51-containing foci in a HUS1-dependent manner; RAD1 has a broader meiotic chromosome distribution that only partially overlaps with RAD9, and RAD1 localization to the XY body and unsynapsed autosomes is HUS1-independent, suggesting RAD1 can function through an alternative mechanism outside the canonical 9-1-1 complex.\",\n      \"method\": \"Conditional Hus1 knockout in mouse testis; immunofluorescence of meiotic chromosome spreads; phenotypic analysis\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with direct localization experiments; single study\",\n      \"pmids\": [\"23468651\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Human HRAD1 (HisHrad1A) has 3'→5' exonuclease activity when expressed and purified from bacteria; the shorter splice variant HisHrad1B lacks this activity; HRAD1 is located on chromosome 5p13.2-13.3.\",\n      \"method\": \"Recombinant protein expression and purification; in vitro exonuclease assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro biochemical assay with purified recombinant protein; single lab, single paper\",\n      \"pmids\": [\"9660799\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Human HRAD1 complements UV sensitivity and G2 checkpoint defects of S. pombe rad1 mutants, establishing that HRAD1 is the functional human ortholog of S. pombe rad1+; HRAD1 protein localizes predominantly to the nucleus and is expressed at high levels in proliferative tissues; mouse Rad1 is associated with meiotic chromosomes during spermatogenesis prophase I.\",\n      \"method\": \"Complementation assay in S. pombe rad1 mutant; nuclear localization by immunofluorescence; meiotic chromosome spread immunostaining\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional complementation plus direct localization experiments; single lab\",\n      \"pmids\": [\"9716408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The mammalian 9-1-1 complex localizes to telomeres in human and mouse cells; HUS1-deficient mouse fibroblasts and thymocytes show severe telomere shortening; 9-1-1 associates with catalytically competent telomerase in cell lysates and acts as a positive regulator of telomerase DNA polymerase activity.\",\n      \"method\": \"Chromatin immunoprecipitation at telomeres; telomere length measurement (Q-FISH and Southern); Co-IP with telomerase; telomerase activity assay\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus telomerase activity assay plus conditional KO phenotype; single lab\",\n      \"pmids\": [\"16890531\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"hRad9, hHus1, and hRad1 (9-1-1 complex) localize as constitutive components of ALT-associated PML bodies (APBs) in ALT cells, colocalizing with telomeric DNA and γ-H2AX; this places the 9-1-1 complex at telomeric DSBs in ALT cells.\",\n      \"method\": \"Immunofluorescence and FISH co-localization; ChIP at telomeres\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct localization experiments; single lab\",\n      \"pmids\": [\"15075340\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RAD1 encodes a conserved checkpoint and DNA repair protein that functions in two distinct capacities: (1) as part of the heterotrimeric 9-1-1 (RAD9-HUS1-RAD1) PCNA-like sliding clamp, which is loaded onto damaged DNA by the RAD17-RFC clamp loader, recruits TopBP1 (via phosphorylated RAD9) to stimulate ATR-mediated CHK1 activation, and serves as a scaffold that stimulates multiple base excision repair enzymes (Pol β, FEN1, DNA ligase I, APE1, NEIL1, TDG, MYH); and (2) in complex with RAD10/ERCC1 as a structure-specific endonuclease that cleaves duplex-single-strand junctions (cutting the 3'-tailed strand) to perform the 5' incision in nucleotide excision repair, remove nonhomologous 3' tails during single-strand annealing and gene conversion DSB repair, and process 3'-blocked termini from oxidative strand breaks.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RAD1 is a conserved DNA repair and checkpoint protein that operates through two structurally and functionally distinct assemblies. In nucleotide excision repair and recombination, Rad1 partners with Rad10 to form a structure-specific endonuclease that degrades single-stranded DNA and cleaves duplex–single-strand junctions on the 3'-tailed strand [#0, #2]; this activity generates 3'-hydroxyl/5'-phosphate termini and performs the 5' incision during NER, reconstituting dual incision when combined with XPG [#1, #4]. Stable Rad1–Rad10 complex formation, mediated by conserved C-terminal hydrophobic domains, is essential for both repair and recombination, since an interaction-defective rad1 allele phenocopies the null [#5, #6]. Genetically, Rad1-Rad10 is specifically required to remove nonhomologous 3' tails during single-strand annealing and gene-conversion DSB repair [#8, #9], to process 3'-blocked termini such as 3'-phosphoglycolate from oxidative breaks [#38], and to repair Top1 cleavage complexes, with the catalytic-dead rad1-D869A mutant confirming the endonuclease requirement [#37]; targeting to lesions and substrates is provided by accessory factors including Rad14 in NER and Saw1 in SSA [#39, #42]. In a second capacity, Rad1 is a subunit of the heterotrimeric 9-1-1 (Rad9-Hus1-Rad1) PCNA-like sliding clamp [#12], whose toroidal ring architecture was confirmed crystallographically [#14]. Rad1 is essential for 9-1-1 integrity and for ATR-dependent (not ATM-dependent) Chk1 activation, with its loss destabilizing Rad9 and Hus1, causing radioresistant DNA synthesis and chromosomal abnormalities [#23]. The clamp is loaded onto damaged chromatin by Rad17 in a proximal, kinase-independent step [#21, #22] and activates Chk1 by positioning TopBP1's activation domain, recruited via CK2-phosphorylated Rad9, to stimulate ATR [#18, #20]. Beyond signaling, 9-1-1 acts as a damage-specific scaffold that stimulates base excision repair enzymes including Pol \\u03b2, FEN1, DNA ligase I, APE1, NEIL1, TDG and MYH through a repair-enzyme-binding site on the Rad1 IDC loop that is competitively blocked by p21 [#14, #15, #25, #28]. The complex also localizes to telomeres and positively regulates telomerase [#49], and contributes to meiotic chromosome surveillance [#46, #48].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Established that Rad1 and Rad10 form an obligate, salt-resistant complex and that this physical association is itself required for repair and recombination, defining Rad1's first functional context.\",\n      \"evidence\": \"Reciprocal Co-IP in vivo and in vitro plus an interaction-defective rad1 allele in yeast, with C-terminal domain mapping by truncation\",\n      \"pmids\": [\"1518857\", \"1620114\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish which subunit carries catalytic activity\", \"Did not define substrate specificity of the complex\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Placed Rad1 genetically at the 3'-end processing step of recombination, showing it removes nonhomologous tails during DSB repair.\",\n      \"evidence\": \"Genetic epistasis with HO-induced DSBs and Southern blot of recombination products in rad1 yeast\",\n      \"pmids\": [\"1411547\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biochemical mechanism of tail removal not yet demonstrated\", \"Did not distinguish NER from recombination roles\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Provided the biochemical basis for Rad1's repair and recombination roles by showing the complex cleaves at duplex–single-strand junctions on the 3'-tailed strand and produces clean termini, unifying the NER incision and tail-removal functions.\",\n      \"evidence\": \"In vitro cleavage of model recombination/repair intermediates and termini analysis with purified Rad1-Rad10\",\n      \"pmids\": [\"8091230\", \"8253764\", \"8479526\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic subunit identity still ambiguous\", \"In vivo lesion-targeting mechanism unaddressed\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Reconstituted the NER dual incision step, demonstrating Rad1-Rad10 performs the 5' incision and cooperates with XPG, and reported failure to detect Holliday junction binding, conflicting with an earlier catalytic-subunit claim.\",\n      \"evidence\": \"In vitro bubble-substrate incision assay with purified Rad1-Rad10 and XPG; negative Holliday junction binding assay\",\n      \"pmids\": [\"7559571\", \"7935767\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conflicting reports on Rad1-only Holliday junction activity unresolved\", \"Substrate selection rules among related nucleases not yet defined\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Showed the recombination role is specific to Rad1-Rad10 among NER factors, separating this sub-pathway from canonical NER.\",\n      \"evidence\": \"Genetic analysis of HO-induced DSB repair across multiple NER deletion strains with physical monitoring\",\n      \"pmids\": [\"7891718\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Factors targeting the nuclease to recombination intermediates unknown\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Identified human HRAD1 as the functional ortholog of fission yeast rad1+ with intrinsic nuclease activity and a checkpoint role, bridging yeast biochemistry to the mammalian checkpoint.\",\n      \"evidence\": \"Complementation of S. pombe rad1 mutants; recombinant 3'\\u21925' exonuclease assay; nuclear localization and meiotic chromosome staining\",\n      \"pmids\": [\"9716408\", \"9660799\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Exonuclease activity from bacterial protein not validated in human cell context\", \"Relationship of human nuclease activity to the 9-1-1 clamp role unclear\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined Rad1's second context as a stable heterotrimeric 9-1-1 clamp and mapped intersubunit contacts, establishing the structural framework for checkpoint and BER functions.\",\n      \"evidence\": \"Reconstitution by co-expression, differential-tag Co-IP, size-exclusion chromatography of the human Rad9-Hus1-Rad1 complex\",\n      \"pmids\": [\"11340080\", \"10359610\", \"9872989\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the ring is loaded onto DNA not yet established\", \"Functional output of the complex undefined at this stage\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Showed 9-1-1 chromatin loading is a proximal, kinase- and replication-independent event, positioning the clamp upstream in the checkpoint cascade.\",\n      \"evidence\": \"Chromatin fractionation with kinase inhibitors and phospho-site mutants in human cells\",\n      \"pmids\": [\"12228248\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Loading machinery not identified in this study\", \"Direct DNA recognition determinants unaddressed\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Established Rad1 as essential for 9-1-1 integrity and ATR-dependent (not ATM-dependent) Chk1 signaling, linking the clamp to genome stability phenotypes.\",\n      \"evidence\": \"siRNA knockdown of RAD1 with complex-stability blots, Chk1 phosphorylation, DNA fiber, and cytogenetic assays\",\n      \"pmids\": [\"15184880\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular intermediary between 9-1-1 and ATR not yet defined here\", \"Distinct contributions of clamp vs nuclease roles to phenotypes not separated\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Revealed a scaffolding function for 9-1-1 in base excision repair by showing it binds and stimulates specific BER enzymes (Pol \\u03b2, FEN1) distinct from PCNA, broadening Rad1's role beyond signaling.\",\n      \"evidence\": \"In vitro pull-down and enzyme stimulation assays with purified 9-1-1 against multiple polymerases and substrates\",\n      \"pmids\": [\"15314187\", \"15556996\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Enzyme-binding surface on the clamp not yet localized\", \"In vivo relevance of stimulation not directly tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined the mechanism of 9-1-1-driven Chk1 activation: the clamp localizes TopBP1's activation domain via phospho-Rad9 to stimulate ATR, with this requirement bypassed by tethering the AD to other chromatin anchors.\",\n      \"evidence\": \"Co-IP, TopBP1-PCNA/H2B fusion bypass experiments, and phospho-Ser373 mutagenesis in human cells and Xenopus extracts\",\n      \"pmids\": [\"17575048\", \"17636252\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for the activating Rad9 phosphorylation not identified here\", \"Spatial coordination with the loader unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Extended the BER scaffold role of 9-1-1 across multiple glycosylases and the AP-endonuclease/long-patch BER pathway, with several enzymes binding through the Rad1/Hus1 subunits.\",\n      \"evidence\": \"Co-IP, in vitro glycosylase/endonuclease stimulation, and LP-BER reconstitution for NEIL1, TDG, MYH and APE1\",\n      \"pmids\": [\"17395641\", \"17855402\", \"16879101\", \"17426133\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether all interactions occur simultaneously or competitively unresolved\", \"In vivo BER contribution of clamp not quantified\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Provided the crystallographic basis for damage-specific 9-1-1 function, locating the repair-enzyme-binding site on the Rad1 IDC loop and showing it is competed by p21, while the Rad9 tail regulates DNA binding.\",\n      \"evidence\": \"X-ray structures of human Rad9-Hus1-Rad1 with FEN1 PIP-box co-crystallization, p21 competition, and truncation DNA-binding assays\",\n      \"pmids\": [\"19446481\", \"19535328\", \"19464297\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of DNA-loaded clamp not resolved\", \"Conformational basis of loader engagement not fully defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Placed Rad17 mechanistically upstream of 9-1-1, showing ATP-dependent loading and CK2 phosphorylation of Rad9 are prerequisites for TopBP1 recruitment and checkpoint activation.\",\n      \"evidence\": \"Xenopus extract biochemistry with Rad17 ATPase mutants and chromatin fractionation; in vitro CK2 kinase assays with phospho-site mutants and UV/MMS sensitivity\",\n      \"pmids\": [\"20110345\", \"20545769\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise order of loading versus TopBP1 binding events partially inferred\", \"Mammalian in vivo loading kinetics not directly measured\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified accessory targeting factors and an alternative meiotic role for Rad1, showing Saw1 directs Rad1-Rad10 to 3'-tailed SSA substrates and that meiotic Rad1 localization can be 9-1-1-independent.\",\n      \"evidence\": \"Reconstituted cleavage with purified Rad1/Rad10 and Saw1, ChIP, and Co-IP; conditional Hus1 knockout mouse meiotic immunofluorescence\",\n      \"pmids\": [\"23299942\", \"18471978\", \"23468651\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular nature of 9-1-1-independent Rad1 meiotic function undefined\", \"Whether human Rad1 uses a Saw1-like targeting factor unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the nuclease (Rad1-Rad10) and checkpoint-clamp (9-1-1) identities of Rad1 are coordinated within a single proteome, and the structural basis of conflicting Holliday-junction observations, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No study reconciles the dual structural assemblies of Rad1 in one system\", \"Conflicting Holliday junction binding reports unresolved\", \"In vivo separation of clamp vs nuclease contributions to mammalian phenotypes incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140097\", \"supporting_discovery_ids\": [0, 1, 2, 4, 37, 38, 44]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 2, 4, 38, 47]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [3, 16]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [12, 14, 15, 25, 31]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [24, 25, 26, 28, 29, 30, 31]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [12, 13, 14]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [7, 11, 48]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [22, 43, 50]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [46, 48, 50]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [2, 4, 25, 31, 38, 39]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [18, 21, 23]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [18, 20, 22, 23]}\n    ],\n    \"complexes\": [\n      \"9-1-1 (Rad9-Hus1-Rad1) clamp\",\n      \"Rad1-Rad10 endonuclease\"\n    ],\n    \"partners\": [\n      \"RAD10\",\n      \"RAD9\",\n      \"HUS1\",\n      \"RAD17\",\n      \"TopBP1\",\n      \"FEN1\",\n      \"RAD14\",\n      \"SAW1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}