{"gene":"RECQL5","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2007,"finding":"RECQL5 binds the RAD51 recombinase and inhibits RAD51-mediated D-loop formation; it displaces RAD51 from single-stranded DNA (ssDNA) in a reaction requiring ATP hydrolysis and RPA, disrupting RAD51 presynaptic filaments to suppress homologous recombination","method":"In vitro biochemical assays with purified proteins, electron microscopy, D-loop formation assays, mouse knockout model with HR reporter","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 — reconstitution with purified proteins + EM + mutagenesis + in vivo genetic data; replicated by multiple subsequent studies","pmids":["18003859"],"is_preprint":false},{"year":2000,"finding":"The RecQ5beta isoform (991 aa) localizes exclusively in the nucleoplasm and interacts with topoisomerases 3alpha and 3beta, but not topoisomerase 1; the shorter alpha and gamma isoforms remain cytoplasmic","method":"Immunocytochemical staining of tagged isoforms expressed in 293EBNA cells; immunoprecipitation","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2/3 — co-IP and immunolocalization; single lab but two orthogonal methods","pmids":["10710432"],"is_preprint":false},{"year":2008,"finding":"RECQL5 (RECQ5) is a bona fide RNAPII-associated protein; the interaction is direct and mediated by the RPB1 subunit of RNAPII, and RECQ5 is the only human RECQ family member that associates with RNAPII","method":"Targeted proteomic analysis of chromatin-associated factors; direct interaction demonstrated by pulldown with purified proteins","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1/2 — direct interaction reconstituted with purified proteins, replicated in multiple subsequent studies","pmids":["18562274"],"is_preprint":false},{"year":2005,"finding":"Recql5 and Blm have nonredundant roles in suppressing sister chromatid exchanges (crossovers) during mitosis; deletion of both genes causes additive increases in SCE frequency beyond either single knockout","method":"Genetic epistasis in mouse ES cells and MEFs; sister chromatid exchange frequency measurement in single and double knockouts","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — clean genetic epistasis with defined cellular phenotype, replicated across cell types","pmids":["15831450"],"is_preprint":false},{"year":2009,"finding":"RECQL5 directly inhibits both initiation and elongation of RNAPII transcription; this inhibition requires the RNAPII-interaction domain of RECQL5 but not its helicase activity","method":"In vitro transcription assays reconstituted with highly purified general transcription factors and RNAPII; RNAPII-interaction-defective RECQL5 mutant","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — fully reconstituted in vitro transcription system with mutagenesis controls","pmids":["19570979"],"is_preprint":false},{"year":2010,"finding":"RECQ5 associates with the Ser2,5-phosphorylated CTD of RPB1 via a Set2-Rpb1-interacting (SRI) motif at the RECQ5 C-terminus; RECQ5 associates with RNAPII-transcribed genes in an SRI-dependent manner correlating with productive elongation","method":"Co-IP, chromatin immunoprecipitation (ChIP), SRI domain mutation analysis, in vitro binding assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1/2 — multiple orthogonal methods (Co-IP, ChIP, in vitro binding) with domain mutagenesis","pmids":["20705653"],"is_preprint":false},{"year":2010,"finding":"RecQL5 interacts with RNAPII through KIX (binds both initiation Pol IIa and elongation Pol IIo forms) and SRI (binds only elongation Pol IIo) domains; both helicase activity and KIX-mediated Pol IIa interaction are required for full genome-stabilizing function","method":"Purification of RecQL5-associated complex; bioinformatics/structural modeling-guided mutagenesis; SCE and camptothecin resistance assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1/2 — biochemical purification, domain mutagenesis, and functional assays in multiple parallel experiments","pmids":["20231364"],"is_preprint":false},{"year":2010,"finding":"Physical interaction between RECQ5 and RAD51 mapped to a specific RAD51-interacting domain of RECQ5; point mutations abolishing RECQ5-RAD51 complex formation impair RAD51 displacement from ssDNA while retaining normal ATPase activity, and ablation of this interaction alleviates RECQ5 inhibition of HR-mediated DSB repair","method":"Domain mapping, point mutagenesis, in vitro RAD51 displacement assays, DSB repair assays in cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro assays with mutagenesis; functional validation in cells","pmids":["20348101"],"is_preprint":false},{"year":2009,"finding":"RECQ5 is constitutively associated with the MRE11-RAD50-NBS1 (MRN) complex through interactions with both MRE11 and NBS1; RECQ5 specifically inhibits the 3'→5' exonuclease activity of MRE11, and the MRN complex is required for recruitment of RECQ5 to sites of DNA damage","method":"Co-IP with purified proteins, in vitro exonuclease inhibition assays, laser-induced DSB recruitment assays, cellular epistasis using MRN-depleted cells","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1/2 — in vitro reconstitution, reciprocal Co-IP, functional cellular assays","pmids":["19270065"],"is_preprint":false},{"year":2011,"finding":"The SRI domain of human RECQ5 is important for suppressing spontaneous DSBs and preventing accumulation of active RNAPII on chromatin; RECQ5 depletion causes RNAPII-dependent DSB formation that is eliminated by transcription inhibition","method":"SRI domain mutants, ChIP for active RNAPII, transcription inhibitor treatment, γH2AX/DSB assays in RECQ5-depleted cells","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (ChIP, DSB assays, inhibitor rescue) with domain mutagenesis","pmids":["21402780"],"is_preprint":false},{"year":2011,"finding":"RECQL5 physically interacts with and stimulates the decatenation activity of Topoisomerase IIα; RECQL5 co-localizes with Topo IIα during S-phase, and RECQL5 depletion causes G2/M arrest, undercondensed/entangled chromosomes, and a late S-phase cycling defect phenocopying Topo II inhibition","method":"Co-IP, in vitro decatenation stimulation assay, co-localization imaging, cell cycle analysis, metaphase spreads in RECQL5-depleted cells","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1/2 — direct biochemical stimulation assay, reciprocal Co-IP, and multiple cellular phenotypes","pmids":["22013166"],"is_preprint":false},{"year":2012,"finding":"RECQL5 contains a BRC repeat variant (BRCv) that mediates RAD51 interaction through two conserved motifs similar to BRCA2-BRC; mutations in either BRCv motif compromise RECQL5 association with RAD51, inhibition of D-loop formation, SCE suppression, and camptothecin resistance","method":"Structural/bioinformatics identification, mutagenesis of BRCv motifs, RAD51 binding assays, D-loop assays, SCE measurement, cell survival assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1/2 — multiple biochemical and cellular assays with defined mutagenesis of interaction domain","pmids":["22645136"],"is_preprint":false},{"year":2013,"finding":"RECQL5 contacts the Rpb1 jaw domain of Pol II at a site overlapping with TFIIS binding; cryo-EM structure of elongating Pol II arrested with RECQL5 shows helicase domain positioned to sterically block elongation; RECQL5 KIX domain has structural similarity to TFIIS and competes with TFIIS for Pol II binding to inhibit transcriptional read-through","method":"Cryo-EM structure determination, crystal structure of KIX domain, in vitro competition assay with TFIIS, TFIIS read-through assay","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure + crystal structure + in vitro functional assays in single study","pmids":["23748380"],"is_preprint":false},{"year":2013,"finding":"RECQL5 promotes formation of non-crossover products during HR by counteracting the inhibitory effect of RAD51 on RAD52-mediated DNA annealing; RECQL5 deficiency causes increased RAD51 occupancy at DSB sites and elevated SCEs upon inactivation of the Holliday junction dissolution pathway","method":"In vitro strand annealing assays with purified proteins, ChIP for RAD51 at DSB sites, SCE measurement in BLM-deficient background, in vivo HR reporter assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1/2 — in vitro reconstitution combined with multiple cellular assays","pmids":["24319145"],"is_preprint":false},{"year":2014,"finding":"RECQL5 controls RNAPII elongation genome-wide; depletion causes increased average RNAPII elongation rate with increased stalling/pausing/backtracking (transcription stress), and leads to chromosomal breakpoints at genes and common fragile sites overlapping with regions of elevated transcription stress","method":"Genome-wide RNAPII ChIP-seq, RNAPII density profiling, genomic copy number analysis, RECQL5 depletion/overexpression","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — genome-wide functional assays with depletion/overexpression showing reciprocal effects; high citation count","pmids":["24836610"],"is_preprint":false},{"year":2015,"finding":"RECQL5 promotes SUMOylation of TOP1 at K391 and K436 by facilitating interaction between the PIAS1-SRSF1 E3 ligase complex and TOP1; this SUMOylation is required for TOP1 binding to active RNAPII (RNAPIIo) and recruitment of RNA splicing factors, reducing R-loop formation; SUMOylation also negatively regulates TOP1 topoisomerase activity at transcriptionally active chromatin","method":"SUMOylation assays, Co-IP, mutagenesis of K391/K436, R-loop measurement, topoisomerase activity assays, chromatin fractionation","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1/2 — biochemical reconstitution of SUMOylation pathway, mutagenesis, multiple functional readouts","pmids":["25851487"],"is_preprint":false},{"year":2016,"finding":"RECQ5 associates with both RNAPI and RNAPII transcription complexes in DNA replication foci; RECQ5 interaction with PCNA promotes RAD18-dependent PCNA ubiquitination; RECQ5 helicase activity promotes processing of replication intermediates at replication-transcription collision sites; RECQ5-deficient cells accumulate RAD18 and BRCA1-dependent RAD51 foci at replication-transcription collision sites","method":"Co-IP, proximity ligation assay, ChIP, laser-induced damage recruitment, PCNA ubiquitination assay, DNA fiber analysis in RECQ5-depleted cells","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods establishing PCNA interaction and functional consequence","pmids":["27502483"],"is_preprint":false},{"year":2017,"finding":"RECQ5 associates with common fragile sites (CFSs) during early mitosis via physical interaction with MUS81; CDK1-dependent Ser727 phosphorylation of RECQ5 is required for this association; RECQ5 promotes MUS81-dependent mitotic DNA synthesis at CFSs by removing RAD51 filaments from stalled replication forks, alleviating RAD51 inhibition of MUS81-EME1 3'-flap cleavage activity","method":"ChIP at CFSs, Co-IP of RECQ5-MUS81, phosphosite mutagenesis (S727A), in vitro 3'-flap cleavage assays with RAD51 ± RECQ5, DNA fiber analysis, mitotic DNA synthesis assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1/2 — in vitro biochemical assay, phospho-mutagenesis, ChIP, and multiple cellular functional assays","pmids":["28575661"],"is_preprint":false},{"year":2017,"finding":"Crystal structures of the RECQL5 core helicase domain in 'Open' and 'Closed' conformations (with and without ADP) reveal the mechano-chemical cycle; SAXS shows the 'Open' form predominates in solution; ATPase, helicase, and DNA binding properties mapped to specific residues and domains","method":"X-ray crystallography, SAXS, in vitro ATPase assay, helicase assay, DNA binding assays with domain variants","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 — crystal structures with functional validation by biochemical assays","pmids":["28100692"],"is_preprint":false},{"year":2021,"finding":"RECQ5 acts as an ATP-dependent ssDNA motor protein, translocating on RPA-coated ssDNA and RAD51-coated ssDNA to dismantle RAD51-ssDNA filaments; protein-protein contact between RECQ5 and RAD51 (RECQ5-F666A mutation) reduces translocation velocity ~50% but RECQ5 can still remove ATP hydrolysis-deficient RAD51-K133R; RECQ5 cannot translocate on dsDNA nor dismantle RAD51-bound heteroduplex joint molecules","method":"Single-molecule imaging (TIRF microscopy), kinetic assays, RECQ5-F666A and RAD51-K133R mutants, ssDNA and dsDNA substrate specificity assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 — single-molecule reconstitution with mutagenesis and substrate specificity analysis","pmids":["33332547"],"is_preprint":false},{"year":2021,"finding":"ATRX-dependent HR outcompetes RECQ5-dependent SDSA for repair of most two-ended DSBs; subpathway choice depends on interaction of both ATRX and RECQ5 with PCNA; RECQ5-dependent SDSA prevents crossover formation (SCE)","method":"Epistasis analysis with ATRX/RECQ5/BLM/MUS81/GEN1 knockouts, SCE measurement, ultra-fine bridge analysis, PCNA interaction mutants","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with multiple knockouts and PCNA interaction mutants; two orthogonal readouts","pmids":["33431668"],"is_preprint":false},{"year":2012,"finding":"RECQL5 physically and functionally interacts with WRN helicase; RECQL5 stimulates WRN helicase activity on DNA fork duplexes; both proteins re-localize from nucleolus to nucleus after replication stress and associate during S-phase; loss of both RECQL5 and WRN is synthetically lethal, severely compromising DNA replication","method":"Co-IP in vivo and in vitro, helicase stimulation assay, live cell imaging, co-localization, double-knockout cell viability assay","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1/2 — in vitro helicase stimulation assay, reciprocal Co-IP, and synthetic lethality with defined replication phenotype","pmids":["23180761"],"is_preprint":false},{"year":2012,"finding":"RECQL5 is recruited early to laser-induced DSBs; both the helicase and KIX domains are required for stable association at DSB sites; recruitment is independent of MDC1, CtIP, BLM, WRN, ATM, RNAPII transcription activity, and MRE11 exonuclease activity, but dependent on MRE11 protein","method":"Live cell confocal microscopy with laser-induced DSBs, domain deletion analysis, epistasis with siRNA knockdowns of damage-response factors","journal":"DNA repair","confidence":"Medium","confidence_rationale":"Tier 2/3 — live imaging with systematic domain and epistasis analysis; single lab","pmids":["22633600"],"is_preprint":false},{"year":2010,"finding":"RECQL5 purifies within an RNAPII holoenzyme complex containing the SWI/SNF chromatin remodeling complex; RECQL5 is detected in the RNAPII holoenzyme but not purified RNAPII core complex","method":"Biochemical purification of RNAPII holoenzyme, mass spectrometry identification","journal":"International journal of biochemistry and molecular biology","confidence":"Medium","confidence_rationale":"Tier 3 — single purification/MS identification; no functional follow-up in this study","pmids":["21968968"],"is_preprint":false},{"year":2015,"finding":"RECQL5 has distinct strand annealing activity: stronger than other human RecQ helicases on long or short substrates, not inhibited by ATP (unlike other RecQs), and efficiently anneals RNA to DNA in vitro; RPA inhibits while RAD51 stimulates RECQL5 strand annealing","method":"In vitro strand annealing assays with purified RECQL5 and all five human RecQ helicases, ATP titration, RNA-DNA annealing, RPA/RAD51/Ku/FEN1 modulation assays","journal":"DNA repair","confidence":"Medium","confidence_rationale":"Tier 1 — in vitro biochemical reconstitution comparing all five RecQ helicases; single lab","pmids":["26717024"],"is_preprint":false},{"year":2016,"finding":"RECQ5 can unfold G-quadruplex (GQ) DNA structures but with ~10-fold weaker activity than BLM and WRN; RECQ5 and BLM have similar ssDNA reeling activities that are not coupled to GQ unfolding","method":"Single-molecule FRET/TIRF assays with various GQ constructs under different salt and ATP conditions","journal":"Biophysical journal","confidence":"Medium","confidence_rationale":"Tier 1 — single-molecule reconstitution; single lab study","pmids":["27332117"],"is_preprint":false},{"year":2015,"finding":"RECQL5 depletion sensitizes JAK2V617F-mutant cells to hydroxyurea and impairs replication dynamics (assessed by DNA fiber analysis) following HU treatment, resulting in increased DSBs and apoptosis specifically in JAK2V617F cells","method":"Single-fiber chromosome combing (DNA fiber analysis), γH2AX/DSB measurement, siRNA depletion of RECQL5 in JAK2V617F vs. wild-type cells","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 — DNA fiber analysis with defined replication phenotype; single lab","pmids":["26686625"],"is_preprint":false},{"year":2015,"finding":"PARP1 and PAR regulate the recruitment and activities of RECQL5; RECQL5 interacts with PAR noncovalently; PARylation is involved in recruitment of RECQL5 to laser-induced DNA damage; RECQL5 loss results in increased sensitivity to PARP inhibition","method":"In vitro PAR-binding assays, laser-induced damage recruitment (live imaging), PARP inhibitor sensitivity assays in RECQL5-depleted cells","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2/3 — in vitro and in vivo assays; single lab with multiple methods","pmids":["26391948"],"is_preprint":false},{"year":2012,"finding":"RECQL5 accumulates at laser-induced single-strand breaks (SSBs) and affects levels of PARP-1 and XRCC1; RECQL5 depletion causes sensitivity to oxidative stress and accumulation of endogenous DNA damage, suggesting RECQL5 modulates base excision repair","method":"Live cell imaging at laser-induced SSBs, PARP/XRCC1 protein level analysis, oxidative stress sensitivity assays in RECQL5-depleted cells","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2/3 — localization at SSBs with functional consequence, but mechanism of BER involvement is indirect","pmids":["22973052"],"is_preprint":false},{"year":2013,"finding":"The KIX domain of RECQL5 (amino acids 500–650) mediates recruitment to psoralen-induced interstrand crosslink sites; recruitment is not affected by transcription or topoisomerase inhibition but is inhibited by DNA-intercalating agents, suggesting the DNA structure itself drives recruitment","method":"Laser-directed confocal microscopy with ICL induction (trioxalen + UVA), domain deletion mapping with KIX truncation, pharmacological inhibitor analysis","journal":"Carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2/3 — domain mapping with live imaging; single lab","pmids":["23715498"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structures of RECQL5 bound to stalled human Pol II elongation complexes reveal: (1) RECQL5 helicase domain acts as a transcriptional roadblock; (2) in nucleotide-free state, RECQL5 twists downstream DNA in the EC; (3) upon nucleotide binding, RECQL5 undergoes a conformational change that allosterically induces Pol II toward a post-translocation state, potentially restarting elongation","method":"Cryo-electron microscopy structure determination of Pol II-RECQL5 elongation complexes in nucleotide-free and nucleotide-bound states","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — high-resolution cryo-EM structures with mechanistic interpretation; two independent concurrent publications","pmids":["40624164"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structures of RECQL5 bound to Pol II elongation complexes identify an α-helix of RECQL5 (brake helix) responsible for binding Pol II and slowing transcription elongation; the TCR complex allows Pol II to overcome RECQL5-induced braking through translocase activity and competition for Pol II engagement; RECQL5 inhibits TCR-mediated Pol II ubiquitination","method":"Cryo-EM structure determination, biochemical transcription elongation assays, TCR complex competition assays, Pol II ubiquitination assays","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structures combined with multiple biochemical functional assays","pmids":["40624163"],"is_preprint":false},{"year":2025,"finding":"RECQL5 localizes to stalled replication fork sites and restricts RAD51-mediated excessive fork reversal to promote unrestrained DNA synthesis; this function requires RECQL5 binding to PCNA, RAD51, and helicase activity, but is independent of its RNAPII interaction; conversely, RECQL5 regulation of transcription elongation is independent of its RAD51 interaction","method":"DNA fiber assays, co-depletion of fork remodelers (SMARCAL1/ZRANB3/HLTF/FBH1), HR-defective RAD51 mutants, PCNA and RNAPII interaction mutants, replication fork reversal assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with multiple fork remodeler knockdowns, domain-separation mutagenesis, DNA fiber analysis","pmids":["41099703"],"is_preprint":false},{"year":2025,"finding":"RECQ5 localizes in the dense fibrillar component of the nucleolus, associates with pre-rRNA processing factors, recognizes pre-rRNA and unwinds dsRNA in vitro; loss of RECQ5 causes accumulation of 47S, 30SL5', and 30S pre-rRNA and reduction of 21S pre-rRNA, and triggers R-loop formation on rDNA with ATR activation","method":"Immunofluorescence/nucleolar fractionation, Co-IP with pre-rRNA processing factors, in vitro dsRNA unwinding assay, Northern blot for pre-rRNA intermediates, R-loop detection (S9.6 antibody/DRIP), ATR activation assay, cancer variant functional analysis","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 1/2 — in vitro dsRNA unwinding reconstitution, localization, and multiple functional readouts; single lab","pmids":["40823811"],"is_preprint":false},{"year":2020,"finding":"KIX domain alternative splicing isoform RECQL5β1 (with 17 extra amino acids) has markedly decreased binding affinity to Pol II and weaker transcription repression activity, but binds more strongly to MRE11 and promotes DNA repair at DSBs, demonstrating functional specialization of KIX isoforms","method":"Co-IP binding affinity comparison, in vitro transcription repression assays, MRE11 binding assays, DSB repair assays in rescue cell lines expressing each isoform","journal":"DNA repair","confidence":"Medium","confidence_rationale":"Tier 2/3 — multiple functional assays comparing isoforms; single lab","pmids":["33197722"],"is_preprint":false},{"year":2025,"finding":"RECQL5 uses a brake helix as a doorstop to control RNAPII translocation (transcription attenuation at atomic level); at mesoscale, RECQL5 forms a condensate scaffold matrix integrating phosphorylated RNAPII elongation complexes through site-specific interactions, reinforcing condensate structural integrity","method":"Biochemical reconstitution, cryo-EM, cryo-electron tomography, coarse-grained molecular simulations","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 — multi-scale structural and biochemical reconstitution; preprint, not yet peer-reviewed","pmids":[],"is_preprint":true}],"current_model":"RECQL5 is a RecQ-family DNA helicase with dual roles: (1) it suppresses homologous recombination by disrupting RAD51 presynaptic filaments on ssDNA in an ATP hydrolysis- and RPA-dependent manner, using a BRC repeat variant and a mapped RAD51-interaction domain, thereby channeling HR toward synthesis-dependent strand annealing and preventing crossovers; and (2) it associates directly with the elongating RNA polymerase II via its SRI domain (binding Ser2,5-phosphorylated RPB1 CTD) and KIX domain, acting as a general transcription elongation factor that slows RNAPII progression—as revealed by cryo-EM structures showing steric blockade and DNA translocation state modulation—thereby preventing transcription stress, R-loop formation, and transcription-replication collisions that would otherwise cause genome instability; additionally, RECQL5 promotes TOP1 SUMOylation, stimulates Topoisomerase IIα decatenation, cooperates with the MRN complex at DSB sites, facilitates MUS81-dependent mitotic DNA synthesis at common fragile sites via CDK1-phosphorylation-dependent RAD51 filament removal, and processes pre-rRNA in the nucleolus."},"narrative":{"teleology":[{"year":2000,"claim":"Establishing that the major RECQL5 isoform (RecQ5β) is a nuclear protein with topoisomerase III interactions resolved basic questions about subcellular context and potential functional partnerships for this poorly characterized RecQ helicase.","evidence":"Immunocytochemistry of tagged isoforms in 293EBNA cells; co-IP with topoisomerase 3α/3β","pmids":["10710432"],"confidence":"Medium","gaps":["Functional significance of Topo3α/3β interaction not tested","Overexpression-based localization may not reflect endogenous protein"]},{"year":2005,"claim":"Genetic evidence that RECQL5 and BLM non-redundantly suppress sister chromatid exchanges established RECQL5 as a bona fide anti-recombinase acting through a pathway distinct from the BLM dissolution mechanism.","evidence":"SCE measurement in Recql5/Blm single and double knockout mouse ES cells and MEFs","pmids":["15831450"],"confidence":"High","gaps":["Biochemical mechanism of SCE suppression unknown at this point","No direct substrate or interaction partner identified"]},{"year":2007,"claim":"Demonstration that RECQL5 directly binds RAD51 and dismantles presynaptic filaments in an ATP- and RPA-dependent manner provided the molecular mechanism for its anti-recombinase activity.","evidence":"In vitro reconstitution with purified proteins, EM visualization of filament disruption, D-loop assays, mouse knockout HR reporter","pmids":["18003859"],"confidence":"High","gaps":["Structural basis of RAD51 interaction not yet mapped","Whether RECQL5 acts as a translocase on ssDNA or uses a different mechanism was unknown"]},{"year":2008,"claim":"Discovery that RECQL5 is the only human RecQ helicase that directly associates with RNAPII revealed an unexpected second functional axis—transcription regulation—distinct from its recombination role.","evidence":"Targeted proteomics of chromatin-associated factors; direct interaction reconstituted with purified RECQL5 and RPB1","pmids":["18562274"],"confidence":"High","gaps":["Domain mediating Pol II interaction not yet mapped","Functional consequence of the interaction unknown"]},{"year":2009,"claim":"Two parallel discoveries defined RECQL5's interactions at DNA damage sites: it constitutively associates with the MRN complex (inhibiting MRE11 exonuclease) and it directly inhibits RNAPII transcription initiation and elongation independent of helicase activity.","evidence":"Co-IP with MRN components, in vitro exonuclease inhibition, laser-induced DSB recruitment (PMID:19270065); reconstituted in vitro transcription with purified GTFs and RNAPII, helicase-dead mutant (PMID:19570979)","pmids":["19270065","19570979"],"confidence":"High","gaps":["Structural basis of MRN interaction not determined","How helicase-independent transcription inhibition is achieved mechanistically was unclear"]},{"year":2010,"claim":"Mapping of the SRI and KIX domains as dual RNAPII-binding modules, and the RAD51-interaction domain as the anti-recombinase interface, established the modular domain architecture underlying RECQL5's bifunctional activities.","evidence":"SRI domain binding to Ser2,5-phospho CTD by ChIP and in vitro binding (PMID:20705653); KIX domain binding Pol IIa/IIo with mutagenesis and SCE assays (PMID:20231364); RAD51-interaction domain point mutants disrupting filament displacement (PMID:20348101)","pmids":["20705653","20231364","20348101"],"confidence":"High","gaps":["Atomic-resolution structures of these domain–partner complexes not yet available","How KIX and SRI domains coordinate during transcription elongation not resolved"]},{"year":2011,"claim":"Connecting RECQL5's SRI-mediated RNAPII association to genome stability showed that loss of RECQL5 causes RNAPII-dependent double-strand breaks, establishing transcription stress as the proximal cause of genomic instability in RECQL5-deficient cells.","evidence":"SRI domain mutants, ChIP for active RNAPII, γH2AX/DSB assays rescued by transcription inhibitors","pmids":["21402780"],"confidence":"High","gaps":["Genomic locations of transcription-dependent breaks not mapped","Whether R-loops mediate the breaks was not tested"]},{"year":2011,"claim":"Discovery that RECQL5 physically stimulates Topoisomerase IIα decatenation activity expanded its functional repertoire beyond recombination and transcription to chromosome topology maintenance during S-phase.","evidence":"Co-IP, in vitro decatenation stimulation assay, co-localization in S-phase, chromosome entanglement phenotype upon RECQL5 depletion","pmids":["22013166"],"confidence":"High","gaps":["Mechanism of stimulation (conformational change vs. recruitment) not determined","Whether this is independent of RECQL5 helicase activity not tested"]},{"year":2012,"claim":"Identification of a BRC repeat variant in RECQL5 that mimics BRCA2's RAD51-binding motifs provided the structural rationale for how RECQL5 engages the RAD51 protomer to disrupt filaments, while WRN interaction studies and DSB recruitment mapping further contextualized RECQL5's role at replication and damage sites.","evidence":"BRCv motif mutagenesis with D-loop, SCE, and binding assays (PMID:22645136); WRN co-IP and helicase stimulation assay, synthetic lethality (PMID:23180761); domain deletion live imaging at laser DSBs (PMID:22633600)","pmids":["22645136","23180761","22633600"],"confidence":"High","gaps":["Crystal structure of BRCv-RAD51 interface not solved","Whether WRN stimulation is direct or mediated through substrate remodeling unclear"]},{"year":2013,"claim":"The first cryo-EM structure of RECQL5 bound to elongating Pol II revealed that its helicase domain sterically blocks the downstream DNA channel while its KIX domain competes with TFIIS, providing the atomic-level explanation for transcription inhibition and crossover suppression via non-crossover HR channeling.","evidence":"Cryo-EM of Pol II–RECQL5, KIX crystal structure, TFIIS competition assay (PMID:23748380); in vitro strand annealing showing RECQL5 counteracts RAD51 inhibition of RAD52-mediated annealing (PMID:24319145)","pmids":["23748380","24319145"],"confidence":"High","gaps":["Resolution insufficient to define brake helix contacts","How RECQL5 switches between transcription-inhibitory and HR-regulatory modes not addressed"]},{"year":2014,"claim":"Genome-wide RNAPII profiling upon RECQL5 depletion demonstrated that RECQL5 acts as a global transcription elongation rate regulator, with its loss causing increased elongation speed coupled with elevated stalling, and chromosomal breaks mapping to actively transcribed genes and fragile sites.","evidence":"Genome-wide RNAPII ChIP-seq, copy number analysis, RECQL5 depletion and overexpression showing reciprocal effects","pmids":["24836610"],"confidence":"High","gaps":["Direct mechanism linking faster elongation to increased stalling not resolved","Whether RECQL5 acts at all genes or a subset preferentially was not fully distinguished"]},{"year":2015,"claim":"Discovery that RECQL5 promotes TOP1 SUMOylation via the PIAS1-SRSF1 complex, enabling TOP1 to associate with active RNAPII and reduce R-loops, connected RECQL5's transcription role to co-transcriptional RNA processing and topological stress management.","evidence":"SUMOylation assays, K391/K436 mutagenesis, R-loop measurement, topoisomerase activity assays, chromatin fractionation","pmids":["25851487"],"confidence":"High","gaps":["Whether RECQL5's helicase activity contributes to this function not tested","How RECQL5 facilitates PIAS1-TOP1 interaction structurally is unknown"]},{"year":2016,"claim":"Establishing that RECQL5 operates at replication-transcription collision sites—associating with both RNAPI/RNAPII complexes in replication foci and promoting PCNA ubiquitination—linked its transcription and replication functions mechanistically.","evidence":"Co-IP, PLA, ChIP, PCNA ubiquitination assay, DNA fiber analysis in RECQL5-depleted cells","pmids":["27502483"],"confidence":"High","gaps":["Direct structural basis of PCNA interaction not mapped","Whether PCNA ubiquitination function is separable from RAD51 displacement not tested"]},{"year":2017,"claim":"Demonstration that CDK1-phosphorylated RECQL5 associates with common fragile sites in early mitosis to remove RAD51 filaments and enable MUS81-dependent mitotic DNA synthesis explained how RECQL5 prevents under-replicated DNA from causing mitotic errors, while crystal structures of the helicase core in open/closed conformations defined the mechanochemical cycle.","evidence":"ChIP at CFSs, S727A phosphomutant, in vitro 3′-flap cleavage with RAD51 ± RECQL5 (PMID:28575661); X-ray crystallography, SAXS, ATPase/helicase assays (PMID:28100692)","pmids":["28575661","28100692"],"confidence":"High","gaps":["Whether phosphorylation at S727 affects other RECQL5 interactions not examined","Structure of full-length RECQL5 including KIX/SRI domains not determined"]},{"year":2021,"claim":"Single-molecule imaging revealed RECQL5 as an ATP-dependent ssDNA translocase that dismantles RAD51 filaments through motor activity on the DNA lattice, while genetic epistasis established that RECQL5-dependent SDSA and ATRX-dependent HR represent competing DSB repair pathways governed by PCNA interaction.","evidence":"Single-molecule TIRF microscopy with RECQL5-F666A and RAD51-K133R mutants (PMID:33332547); epistasis with ATRX/BLM/MUS81/GEN1 knockouts and PCNA mutants (PMID:33431668)","pmids":["33332547","33431668"],"confidence":"High","gaps":["How PCNA interaction governs pathway choice mechanistically is unclear","Whether RECQL5 translocase activity contributes to transcription regulation not tested"]},{"year":2025,"claim":"High-resolution cryo-EM structures of RECQL5 on stalled Pol II elongation complexes identified the brake helix as the key structural element controlling translocation, showed nucleotide-dependent conformational switching that can restart paused Pol II, and revealed that the TCR complex competes with RECQL5 for Pol II engagement; separately, RECQL5 was shown to restrict RAD51-mediated fork reversal independently of its RNAPII interaction, and to function in pre-rRNA processing in the nucleolus.","evidence":"Cryo-EM in nucleotide-free and bound states (PMID:40624164, PMID:40624163); DNA fiber assays with fork remodeler co-depletions and domain-separation mutants (PMID:41099703); nucleolar localization, dsRNA unwinding, Northern blots for pre-rRNA (PMID:40823811)","pmids":["40624164","40624163","41099703","40823811"],"confidence":"High","gaps":["Full-length RECQL5 structure including all regulatory domains on Pol II not yet resolved","Mechanism of nucleolar pre-rRNA processing function requires reconstitution","Whether condensate formation is physiologically relevant awaits in vivo validation"]},{"year":null,"claim":"Major unresolved questions include: how RECQL5 switches between its separable transcription-regulatory and recombination/replication functions in vivo; the structural basis of RECQL5 engagement with PCNA, MRN, and Topo IIα; and whether RECQL5's nucleolar rRNA processing role is mechanistically linked to its genome maintenance functions.","evidence":"","pmids":[],"confidence":"High","gaps":["No in vivo structural data for full-length RECQL5 in complex with any partner","Regulation of RECQL5 by post-translational modifications beyond S727 phosphorylation largely unexplored","Pathological consequences of RECQL5 loss in human disease not established through genetic studies"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[0,18,19]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[18,19,25]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[33]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[33]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,19]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,14,30,31]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,7,11,19]}],"localization":[{"term_id":"GO:0005654","term_label":"nucleoplasm","supporting_discovery_ids":[1,22]},{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[21,33]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[5,14,17]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,7,11,13,17,20]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[4,5,6,9,12,14,30,31]},{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[16,26,32]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[33]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[10,17]}],"complexes":["RNAPII elongation complex","MRN complex (associated)"],"partners":["RAD51","RPB1","MRE11","NBS1","TOP2A","MUS81","WRN","PCNA"],"other_free_text":[]},"mechanistic_narrative":"RECQL5 is a RecQ-family DNA helicase that serves as a dual-function genome stability factor, operating both as a regulator of homologous recombination and as a transcription elongation modulator for RNA polymerase II. In its recombination role, RECQL5 acts as an ATP-dependent ssDNA translocase that disrupts RAD51 presynaptic filaments via a BRC repeat variant and a mapped RAD51-interaction domain, channeling double-strand break repair toward synthesis-dependent strand annealing and suppressing crossovers; this activity also extends to removing RAD51 from stalled replication forks to restrict excessive fork reversal and to enabling MUS81-dependent mitotic DNA synthesis at common fragile sites through CDK1-phosphorylation-dependent recruitment [PMID:18003859, PMID:22645136, PMID:33332547, PMID:28575661, PMID:41099703]. In its transcription role, RECQL5 binds elongating RNAPII through KIX and SRI domains—the latter recognizing the Ser2,5-phosphorylated CTD of RPB1—and acts as a steric brake on elongation, as demonstrated by cryo-EM structures showing its helicase domain blocking the downstream DNA channel and a brake helix controlling translocation; loss of this function causes transcription stress, R-loop accumulation, and replication-transcription collisions that generate DNA breaks at actively transcribed loci and fragile sites [PMID:20705653, PMID:24836610, PMID:40624164, PMID:40624163]. RECQL5 additionally promotes TOP1 SUMOylation to facilitate proper co-transcriptional RNA processing and R-loop resolution, stimulates Topoisomerase IIα decatenation activity during S-phase, cooperates with the MRN complex at DSB sites, and processes pre-rRNA in the nucleolus [PMID:25851487, PMID:22013166, PMID:19270065, PMID:40823811]."},"prefetch_data":{"uniprot":{"accession":"O94762","full_name":"ATP-dependent DNA helicase Q5","aliases":["DNA 3'-5' helicase RecQ5","DNA helicase, RecQ-like type 5","RecQ5","RecQ protein-like 5"],"length_aa":991,"mass_kda":108.9,"function":"DNA helicase that plays an important role in DNA replication, transcription and repair (PubMed:20643585, PubMed:22973052, PubMed:28100692). Probably unwinds DNA in a 3'-5' direction (Probable) (PubMed:28100692). Binds to the RNA polymerase II subunit POLR2A during transcription elongation and suppresses transcription-associated genomic instability (PubMed:20231364). Also associates with POLR1A and enforces the stability of ribosomal DNA arrays (PubMed:27502483). Plays an important role in mitotic chromosome separation after cross-over events and cell cycle progress (PubMed:22013166). Mechanistically, removes RAD51 filaments protecting stalled replication forks at common fragile sites and stimulates MUS81-EME1 endonuclease leading to mitotic DNA synthesis (PubMed:28575661). Required for efficient DNA repair, including repair of inter-strand cross-links (PubMed:23715498). Stimulates DNA decatenation mediated by TOP2A. Prevents sister chromatid exchange and homologous recombination. A core helicase fragment (residues 11-609) binds preferentially to splayed duplex, looped and ssDNA (PubMed:28100692)","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/O94762/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RECQL5","classification":"Not Classified","n_dependent_lines":12,"n_total_lines":1208,"dependency_fraction":0.009933774834437087},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RECQL5","total_profiled":1310},"omim":[{"mim_id":"614695","title":"REGULATION OF NUCLEAR PRE-mRNA DOMAIN-CONTAINING 2; RPRD2","url":"https://www.omim.org/entry/614695"},{"mim_id":"614694","title":"REGULATION OF NUCLEAR PRE-mRNA DOMAIN-CONTAINING PROTEIN 1B; RPRD1B","url":"https://www.omim.org/entry/614694"},{"mim_id":"610347","title":"REGULATION OF NUCLEAR PRE-mRNA DOMAIN-CONTAINING PROTEIN 1A; RPRD1A","url":"https://www.omim.org/entry/610347"},{"mim_id":"604611","title":"RECQ PROTEIN-LIKE 2; RECQL2","url":"https://www.omim.org/entry/604611"},{"mim_id":"604610","title":"RECQ PROTEIN-LIKE 3; RECQL3","url":"https://www.omim.org/entry/604610"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RECQL5"},"hgnc":{"alias_symbol":["RecQ5","FLJ90603"],"prev_symbol":[]},"alphafold":{"accession":"O94762","domains":[{"cath_id":"3.40.50.300","chopping":"11-216","consensus_level":"high","plddt":92.6362,"start":11,"end":216},{"cath_id":"3.40.50.300","chopping":"224-445","consensus_level":"medium","plddt":92.0012,"start":224,"end":445},{"cath_id":"-","chopping":"911-985","consensus_level":"high","plddt":84.8612,"start":911,"end":985},{"cath_id":"1.10.8","chopping":"546-611","consensus_level":"high","plddt":84.3909,"start":546,"end":611}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O94762","model_url":"https://alphafold.ebi.ac.uk/files/AF-O94762-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O94762-F1-predicted_aligned_error_v6.png","plddt_mean":70.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RECQL5","jax_strain_url":"https://www.jax.org/strain/search?query=RECQL5"},"sequence":{"accession":"O94762","fasta_url":"https://rest.uniprot.org/uniprotkb/O94762.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O94762/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O94762"}},"corpus_meta":[{"pmid":"18003859","id":"PMC_18003859","title":"RECQL5/Recql5 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Promote Non-Homologous End Joining Repair of DNA Double Strand Breaks During V(D)J Recombination","date":"2024-09-26","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.25.615014","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":37226,"output_tokens":8417,"usd":0.118967},"stage2":{"model":"claude-opus-4-6","input_tokens":12226,"output_tokens":4684,"usd":0.267345},"total_usd":0.386312,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"RECQL5 binds the RAD51 recombinase and inhibits RAD51-mediated D-loop formation; it displaces RAD51 from single-stranded DNA (ssDNA) in a reaction requiring ATP hydrolysis and RPA, disrupting RAD51 presynaptic filaments to suppress homologous recombination\",\n      \"method\": \"In vitro biochemical assays with purified proteins, electron microscopy, D-loop formation assays, mouse knockout model with HR reporter\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution with purified proteins + EM + mutagenesis + in vivo genetic data; replicated by multiple subsequent studies\",\n      \"pmids\": [\"18003859\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The RecQ5beta isoform (991 aa) localizes exclusively in the nucleoplasm and interacts with topoisomerases 3alpha and 3beta, but not topoisomerase 1; the shorter alpha and gamma isoforms remain cytoplasmic\",\n      \"method\": \"Immunocytochemical staining of tagged isoforms expressed in 293EBNA cells; immunoprecipitation\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — co-IP and immunolocalization; single lab but two orthogonal methods\",\n      \"pmids\": [\"10710432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"RECQL5 (RECQ5) is a bona fide RNAPII-associated protein; the interaction is direct and mediated by the RPB1 subunit of RNAPII, and RECQ5 is the only human RECQ family member that associates with RNAPII\",\n      \"method\": \"Targeted proteomic analysis of chromatin-associated factors; direct interaction demonstrated by pulldown with purified proteins\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — direct interaction reconstituted with purified proteins, replicated in multiple subsequent studies\",\n      \"pmids\": [\"18562274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Recql5 and Blm have nonredundant roles in suppressing sister chromatid exchanges (crossovers) during mitosis; deletion of both genes causes additive increases in SCE frequency beyond either single knockout\",\n      \"method\": \"Genetic epistasis in mouse ES cells and MEFs; sister chromatid exchange frequency measurement in single and double knockouts\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic epistasis with defined cellular phenotype, replicated across cell types\",\n      \"pmids\": [\"15831450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RECQL5 directly inhibits both initiation and elongation of RNAPII transcription; this inhibition requires the RNAPII-interaction domain of RECQL5 but not its helicase activity\",\n      \"method\": \"In vitro transcription assays reconstituted with highly purified general transcription factors and RNAPII; RNAPII-interaction-defective RECQL5 mutant\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — fully reconstituted in vitro transcription system with mutagenesis controls\",\n      \"pmids\": [\"19570979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RECQ5 associates with the Ser2,5-phosphorylated CTD of RPB1 via a Set2-Rpb1-interacting (SRI) motif at the RECQ5 C-terminus; RECQ5 associates with RNAPII-transcribed genes in an SRI-dependent manner correlating with productive elongation\",\n      \"method\": \"Co-IP, chromatin immunoprecipitation (ChIP), SRI domain mutation analysis, in vitro binding assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — multiple orthogonal methods (Co-IP, ChIP, in vitro binding) with domain mutagenesis\",\n      \"pmids\": [\"20705653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RecQL5 interacts with RNAPII through KIX (binds both initiation Pol IIa and elongation Pol IIo forms) and SRI (binds only elongation Pol IIo) domains; both helicase activity and KIX-mediated Pol IIa interaction are required for full genome-stabilizing function\",\n      \"method\": \"Purification of RecQL5-associated complex; bioinformatics/structural modeling-guided mutagenesis; SCE and camptothecin resistance assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — biochemical purification, domain mutagenesis, and functional assays in multiple parallel experiments\",\n      \"pmids\": [\"20231364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Physical interaction between RECQ5 and RAD51 mapped to a specific RAD51-interacting domain of RECQ5; point mutations abolishing RECQ5-RAD51 complex formation impair RAD51 displacement from ssDNA while retaining normal ATPase activity, and ablation of this interaction alleviates RECQ5 inhibition of HR-mediated DSB repair\",\n      \"method\": \"Domain mapping, point mutagenesis, in vitro RAD51 displacement assays, DSB repair assays in cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro assays with mutagenesis; functional validation in cells\",\n      \"pmids\": [\"20348101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RECQ5 is constitutively associated with the MRE11-RAD50-NBS1 (MRN) complex through interactions with both MRE11 and NBS1; RECQ5 specifically inhibits the 3'→5' exonuclease activity of MRE11, and the MRN complex is required for recruitment of RECQ5 to sites of DNA damage\",\n      \"method\": \"Co-IP with purified proteins, in vitro exonuclease inhibition assays, laser-induced DSB recruitment assays, cellular epistasis using MRN-depleted cells\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — in vitro reconstitution, reciprocal Co-IP, functional cellular assays\",\n      \"pmids\": [\"19270065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The SRI domain of human RECQ5 is important for suppressing spontaneous DSBs and preventing accumulation of active RNAPII on chromatin; RECQ5 depletion causes RNAPII-dependent DSB formation that is eliminated by transcription inhibition\",\n      \"method\": \"SRI domain mutants, ChIP for active RNAPII, transcription inhibitor treatment, γH2AX/DSB assays in RECQ5-depleted cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (ChIP, DSB assays, inhibitor rescue) with domain mutagenesis\",\n      \"pmids\": [\"21402780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RECQL5 physically interacts with and stimulates the decatenation activity of Topoisomerase IIα; RECQL5 co-localizes with Topo IIα during S-phase, and RECQL5 depletion causes G2/M arrest, undercondensed/entangled chromosomes, and a late S-phase cycling defect phenocopying Topo II inhibition\",\n      \"method\": \"Co-IP, in vitro decatenation stimulation assay, co-localization imaging, cell cycle analysis, metaphase spreads in RECQL5-depleted cells\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — direct biochemical stimulation assay, reciprocal Co-IP, and multiple cellular phenotypes\",\n      \"pmids\": [\"22013166\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RECQL5 contains a BRC repeat variant (BRCv) that mediates RAD51 interaction through two conserved motifs similar to BRCA2-BRC; mutations in either BRCv motif compromise RECQL5 association with RAD51, inhibition of D-loop formation, SCE suppression, and camptothecin resistance\",\n      \"method\": \"Structural/bioinformatics identification, mutagenesis of BRCv motifs, RAD51 binding assays, D-loop assays, SCE measurement, cell survival assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — multiple biochemical and cellular assays with defined mutagenesis of interaction domain\",\n      \"pmids\": [\"22645136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"RECQL5 contacts the Rpb1 jaw domain of Pol II at a site overlapping with TFIIS binding; cryo-EM structure of elongating Pol II arrested with RECQL5 shows helicase domain positioned to sterically block elongation; RECQL5 KIX domain has structural similarity to TFIIS and competes with TFIIS for Pol II binding to inhibit transcriptional read-through\",\n      \"method\": \"Cryo-EM structure determination, crystal structure of KIX domain, in vitro competition assay with TFIIS, TFIIS read-through assay\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure + crystal structure + in vitro functional assays in single study\",\n      \"pmids\": [\"23748380\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"RECQL5 promotes formation of non-crossover products during HR by counteracting the inhibitory effect of RAD51 on RAD52-mediated DNA annealing; RECQL5 deficiency causes increased RAD51 occupancy at DSB sites and elevated SCEs upon inactivation of the Holliday junction dissolution pathway\",\n      \"method\": \"In vitro strand annealing assays with purified proteins, ChIP for RAD51 at DSB sites, SCE measurement in BLM-deficient background, in vivo HR reporter assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — in vitro reconstitution combined with multiple cellular assays\",\n      \"pmids\": [\"24319145\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RECQL5 controls RNAPII elongation genome-wide; depletion causes increased average RNAPII elongation rate with increased stalling/pausing/backtracking (transcription stress), and leads to chromosomal breakpoints at genes and common fragile sites overlapping with regions of elevated transcription stress\",\n      \"method\": \"Genome-wide RNAPII ChIP-seq, RNAPII density profiling, genomic copy number analysis, RECQL5 depletion/overexpression\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide functional assays with depletion/overexpression showing reciprocal effects; high citation count\",\n      \"pmids\": [\"24836610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RECQL5 promotes SUMOylation of TOP1 at K391 and K436 by facilitating interaction between the PIAS1-SRSF1 E3 ligase complex and TOP1; this SUMOylation is required for TOP1 binding to active RNAPII (RNAPIIo) and recruitment of RNA splicing factors, reducing R-loop formation; SUMOylation also negatively regulates TOP1 topoisomerase activity at transcriptionally active chromatin\",\n      \"method\": \"SUMOylation assays, Co-IP, mutagenesis of K391/K436, R-loop measurement, topoisomerase activity assays, chromatin fractionation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — biochemical reconstitution of SUMOylation pathway, mutagenesis, multiple functional readouts\",\n      \"pmids\": [\"25851487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"RECQ5 associates with both RNAPI and RNAPII transcription complexes in DNA replication foci; RECQ5 interaction with PCNA promotes RAD18-dependent PCNA ubiquitination; RECQ5 helicase activity promotes processing of replication intermediates at replication-transcription collision sites; RECQ5-deficient cells accumulate RAD18 and BRCA1-dependent RAD51 foci at replication-transcription collision sites\",\n      \"method\": \"Co-IP, proximity ligation assay, ChIP, laser-induced damage recruitment, PCNA ubiquitination assay, DNA fiber analysis in RECQ5-depleted cells\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods establishing PCNA interaction and functional consequence\",\n      \"pmids\": [\"27502483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RECQ5 associates with common fragile sites (CFSs) during early mitosis via physical interaction with MUS81; CDK1-dependent Ser727 phosphorylation of RECQ5 is required for this association; RECQ5 promotes MUS81-dependent mitotic DNA synthesis at CFSs by removing RAD51 filaments from stalled replication forks, alleviating RAD51 inhibition of MUS81-EME1 3'-flap cleavage activity\",\n      \"method\": \"ChIP at CFSs, Co-IP of RECQ5-MUS81, phosphosite mutagenesis (S727A), in vitro 3'-flap cleavage assays with RAD51 ± RECQ5, DNA fiber analysis, mitotic DNA synthesis assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — in vitro biochemical assay, phospho-mutagenesis, ChIP, and multiple cellular functional assays\",\n      \"pmids\": [\"28575661\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Crystal structures of the RECQL5 core helicase domain in 'Open' and 'Closed' conformations (with and without ADP) reveal the mechano-chemical cycle; SAXS shows the 'Open' form predominates in solution; ATPase, helicase, and DNA binding properties mapped to specific residues and domains\",\n      \"method\": \"X-ray crystallography, SAXS, in vitro ATPase assay, helicase assay, DNA binding assays with domain variants\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structures with functional validation by biochemical assays\",\n      \"pmids\": [\"28100692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RECQ5 acts as an ATP-dependent ssDNA motor protein, translocating on RPA-coated ssDNA and RAD51-coated ssDNA to dismantle RAD51-ssDNA filaments; protein-protein contact between RECQ5 and RAD51 (RECQ5-F666A mutation) reduces translocation velocity ~50% but RECQ5 can still remove ATP hydrolysis-deficient RAD51-K133R; RECQ5 cannot translocate on dsDNA nor dismantle RAD51-bound heteroduplex joint molecules\",\n      \"method\": \"Single-molecule imaging (TIRF microscopy), kinetic assays, RECQ5-F666A and RAD51-K133R mutants, ssDNA and dsDNA substrate specificity assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — single-molecule reconstitution with mutagenesis and substrate specificity analysis\",\n      \"pmids\": [\"33332547\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ATRX-dependent HR outcompetes RECQ5-dependent SDSA for repair of most two-ended DSBs; subpathway choice depends on interaction of both ATRX and RECQ5 with PCNA; RECQ5-dependent SDSA prevents crossover formation (SCE)\",\n      \"method\": \"Epistasis analysis with ATRX/RECQ5/BLM/MUS81/GEN1 knockouts, SCE measurement, ultra-fine bridge analysis, PCNA interaction mutants\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with multiple knockouts and PCNA interaction mutants; two orthogonal readouts\",\n      \"pmids\": [\"33431668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RECQL5 physically and functionally interacts with WRN helicase; RECQL5 stimulates WRN helicase activity on DNA fork duplexes; both proteins re-localize from nucleolus to nucleus after replication stress and associate during S-phase; loss of both RECQL5 and WRN is synthetically lethal, severely compromising DNA replication\",\n      \"method\": \"Co-IP in vivo and in vitro, helicase stimulation assay, live cell imaging, co-localization, double-knockout cell viability assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — in vitro helicase stimulation assay, reciprocal Co-IP, and synthetic lethality with defined replication phenotype\",\n      \"pmids\": [\"23180761\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RECQL5 is recruited early to laser-induced DSBs; both the helicase and KIX domains are required for stable association at DSB sites; recruitment is independent of MDC1, CtIP, BLM, WRN, ATM, RNAPII transcription activity, and MRE11 exonuclease activity, but dependent on MRE11 protein\",\n      \"method\": \"Live cell confocal microscopy with laser-induced DSBs, domain deletion analysis, epistasis with siRNA knockdowns of damage-response factors\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — live imaging with systematic domain and epistasis analysis; single lab\",\n      \"pmids\": [\"22633600\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RECQL5 purifies within an RNAPII holoenzyme complex containing the SWI/SNF chromatin remodeling complex; RECQL5 is detected in the RNAPII holoenzyme but not purified RNAPII core complex\",\n      \"method\": \"Biochemical purification of RNAPII holoenzyme, mass spectrometry identification\",\n      \"journal\": \"International journal of biochemistry and molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single purification/MS identification; no functional follow-up in this study\",\n      \"pmids\": [\"21968968\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RECQL5 has distinct strand annealing activity: stronger than other human RecQ helicases on long or short substrates, not inhibited by ATP (unlike other RecQs), and efficiently anneals RNA to DNA in vitro; RPA inhibits while RAD51 stimulates RECQL5 strand annealing\",\n      \"method\": \"In vitro strand annealing assays with purified RECQL5 and all five human RecQ helicases, ATP titration, RNA-DNA annealing, RPA/RAD51/Ku/FEN1 modulation assays\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical reconstitution comparing all five RecQ helicases; single lab\",\n      \"pmids\": [\"26717024\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"RECQ5 can unfold G-quadruplex (GQ) DNA structures but with ~10-fold weaker activity than BLM and WRN; RECQ5 and BLM have similar ssDNA reeling activities that are not coupled to GQ unfolding\",\n      \"method\": \"Single-molecule FRET/TIRF assays with various GQ constructs under different salt and ATP conditions\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — single-molecule reconstitution; single lab study\",\n      \"pmids\": [\"27332117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RECQL5 depletion sensitizes JAK2V617F-mutant cells to hydroxyurea and impairs replication dynamics (assessed by DNA fiber analysis) following HU treatment, resulting in increased DSBs and apoptosis specifically in JAK2V617F cells\",\n      \"method\": \"Single-fiber chromosome combing (DNA fiber analysis), γH2AX/DSB measurement, siRNA depletion of RECQL5 in JAK2V617F vs. wild-type cells\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — DNA fiber analysis with defined replication phenotype; single lab\",\n      \"pmids\": [\"26686625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PARP1 and PAR regulate the recruitment and activities of RECQL5; RECQL5 interacts with PAR noncovalently; PARylation is involved in recruitment of RECQL5 to laser-induced DNA damage; RECQL5 loss results in increased sensitivity to PARP inhibition\",\n      \"method\": \"In vitro PAR-binding assays, laser-induced damage recruitment (live imaging), PARP inhibitor sensitivity assays in RECQL5-depleted cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — in vitro and in vivo assays; single lab with multiple methods\",\n      \"pmids\": [\"26391948\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RECQL5 accumulates at laser-induced single-strand breaks (SSBs) and affects levels of PARP-1 and XRCC1; RECQL5 depletion causes sensitivity to oxidative stress and accumulation of endogenous DNA damage, suggesting RECQL5 modulates base excision repair\",\n      \"method\": \"Live cell imaging at laser-induced SSBs, PARP/XRCC1 protein level analysis, oxidative stress sensitivity assays in RECQL5-depleted cells\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — localization at SSBs with functional consequence, but mechanism of BER involvement is indirect\",\n      \"pmids\": [\"22973052\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The KIX domain of RECQL5 (amino acids 500–650) mediates recruitment to psoralen-induced interstrand crosslink sites; recruitment is not affected by transcription or topoisomerase inhibition but is inhibited by DNA-intercalating agents, suggesting the DNA structure itself drives recruitment\",\n      \"method\": \"Laser-directed confocal microscopy with ICL induction (trioxalen + UVA), domain deletion mapping with KIX truncation, pharmacological inhibitor analysis\",\n      \"journal\": \"Carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — domain mapping with live imaging; single lab\",\n      \"pmids\": [\"23715498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structures of RECQL5 bound to stalled human Pol II elongation complexes reveal: (1) RECQL5 helicase domain acts as a transcriptional roadblock; (2) in nucleotide-free state, RECQL5 twists downstream DNA in the EC; (3) upon nucleotide binding, RECQL5 undergoes a conformational change that allosterically induces Pol II toward a post-translocation state, potentially restarting elongation\",\n      \"method\": \"Cryo-electron microscopy structure determination of Pol II-RECQL5 elongation complexes in nucleotide-free and nucleotide-bound states\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution cryo-EM structures with mechanistic interpretation; two independent concurrent publications\",\n      \"pmids\": [\"40624164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structures of RECQL5 bound to Pol II elongation complexes identify an α-helix of RECQL5 (brake helix) responsible for binding Pol II and slowing transcription elongation; the TCR complex allows Pol II to overcome RECQL5-induced braking through translocase activity and competition for Pol II engagement; RECQL5 inhibits TCR-mediated Pol II ubiquitination\",\n      \"method\": \"Cryo-EM structure determination, biochemical transcription elongation assays, TCR complex competition assays, Pol II ubiquitination assays\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structures combined with multiple biochemical functional assays\",\n      \"pmids\": [\"40624163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RECQL5 localizes to stalled replication fork sites and restricts RAD51-mediated excessive fork reversal to promote unrestrained DNA synthesis; this function requires RECQL5 binding to PCNA, RAD51, and helicase activity, but is independent of its RNAPII interaction; conversely, RECQL5 regulation of transcription elongation is independent of its RAD51 interaction\",\n      \"method\": \"DNA fiber assays, co-depletion of fork remodelers (SMARCAL1/ZRANB3/HLTF/FBH1), HR-defective RAD51 mutants, PCNA and RNAPII interaction mutants, replication fork reversal assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with multiple fork remodeler knockdowns, domain-separation mutagenesis, DNA fiber analysis\",\n      \"pmids\": [\"41099703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RECQ5 localizes in the dense fibrillar component of the nucleolus, associates with pre-rRNA processing factors, recognizes pre-rRNA and unwinds dsRNA in vitro; loss of RECQ5 causes accumulation of 47S, 30SL5', and 30S pre-rRNA and reduction of 21S pre-rRNA, and triggers R-loop formation on rDNA with ATR activation\",\n      \"method\": \"Immunofluorescence/nucleolar fractionation, Co-IP with pre-rRNA processing factors, in vitro dsRNA unwinding assay, Northern blot for pre-rRNA intermediates, R-loop detection (S9.6 antibody/DRIP), ATR activation assay, cancer variant functional analysis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1/2 — in vitro dsRNA unwinding reconstitution, localization, and multiple functional readouts; single lab\",\n      \"pmids\": [\"40823811\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"KIX domain alternative splicing isoform RECQL5β1 (with 17 extra amino acids) has markedly decreased binding affinity to Pol II and weaker transcription repression activity, but binds more strongly to MRE11 and promotes DNA repair at DSBs, demonstrating functional specialization of KIX isoforms\",\n      \"method\": \"Co-IP binding affinity comparison, in vitro transcription repression assays, MRE11 binding assays, DSB repair assays in rescue cell lines expressing each isoform\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — multiple functional assays comparing isoforms; single lab\",\n      \"pmids\": [\"33197722\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RECQL5 uses a brake helix as a doorstop to control RNAPII translocation (transcription attenuation at atomic level); at mesoscale, RECQL5 forms a condensate scaffold matrix integrating phosphorylated RNAPII elongation complexes through site-specific interactions, reinforcing condensate structural integrity\",\n      \"method\": \"Biochemical reconstitution, cryo-EM, cryo-electron tomography, coarse-grained molecular simulations\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — multi-scale structural and biochemical reconstitution; preprint, not yet peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"RECQL5 is a RecQ-family DNA helicase with dual roles: (1) it suppresses homologous recombination by disrupting RAD51 presynaptic filaments on ssDNA in an ATP hydrolysis- and RPA-dependent manner, using a BRC repeat variant and a mapped RAD51-interaction domain, thereby channeling HR toward synthesis-dependent strand annealing and preventing crossovers; and (2) it associates directly with the elongating RNA polymerase II via its SRI domain (binding Ser2,5-phosphorylated RPB1 CTD) and KIX domain, acting as a general transcription elongation factor that slows RNAPII progression—as revealed by cryo-EM structures showing steric blockade and DNA translocation state modulation—thereby preventing transcription stress, R-loop formation, and transcription-replication collisions that would otherwise cause genome instability; additionally, RECQL5 promotes TOP1 SUMOylation, stimulates Topoisomerase IIα decatenation, cooperates with the MRN complex at DSB sites, facilitates MUS81-dependent mitotic DNA synthesis at common fragile sites via CDK1-phosphorylation-dependent RAD51 filament removal, and processes pre-rRNA in the nucleolus.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"RECQL5 is a RecQ-family DNA helicase that serves as a dual-function genome stability factor, operating both as a regulator of homologous recombination and as a transcription elongation modulator for RNA polymerase II. In its recombination role, RECQL5 acts as an ATP-dependent ssDNA translocase that disrupts RAD51 presynaptic filaments via a BRC repeat variant and a mapped RAD51-interaction domain, channeling double-strand break repair toward synthesis-dependent strand annealing and suppressing crossovers; this activity also extends to removing RAD51 from stalled replication forks to restrict excessive fork reversal and to enabling MUS81-dependent mitotic DNA synthesis at common fragile sites through CDK1-phosphorylation-dependent recruitment [PMID:18003859, PMID:22645136, PMID:33332547, PMID:28575661, PMID:41099703]. In its transcription role, RECQL5 binds elongating RNAPII through KIX and SRI domains—the latter recognizing the Ser2,5-phosphorylated CTD of RPB1—and acts as a steric brake on elongation, as demonstrated by cryo-EM structures showing its helicase domain blocking the downstream DNA channel and a brake helix controlling translocation; loss of this function causes transcription stress, R-loop accumulation, and replication-transcription collisions that generate DNA breaks at actively transcribed loci and fragile sites [PMID:20705653, PMID:24836610, PMID:40624164, PMID:40624163]. RECQL5 additionally promotes TOP1 SUMOylation to facilitate proper co-transcriptional RNA processing and R-loop resolution, stimulates Topoisomerase IIα decatenation activity during S-phase, cooperates with the MRN complex at DSB sites, and processes pre-rRNA in the nucleolus [PMID:25851487, PMID:22013166, PMID:19270065, PMID:40823811].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing that the major RECQL5 isoform (RecQ5β) is a nuclear protein with topoisomerase III interactions resolved basic questions about subcellular context and potential functional partnerships for this poorly characterized RecQ helicase.\",\n      \"evidence\": \"Immunocytochemistry of tagged isoforms in 293EBNA cells; co-IP with topoisomerase 3α/3β\",\n      \"pmids\": [\"10710432\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional significance of Topo3α/3β interaction not tested\", \"Overexpression-based localization may not reflect endogenous protein\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Genetic evidence that RECQL5 and BLM non-redundantly suppress sister chromatid exchanges established RECQL5 as a bona fide anti-recombinase acting through a pathway distinct from the BLM dissolution mechanism.\",\n      \"evidence\": \"SCE measurement in Recql5/Blm single and double knockout mouse ES cells and MEFs\",\n      \"pmids\": [\"15831450\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biochemical mechanism of SCE suppression unknown at this point\", \"No direct substrate or interaction partner identified\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstration that RECQL5 directly binds RAD51 and dismantles presynaptic filaments in an ATP- and RPA-dependent manner provided the molecular mechanism for its anti-recombinase activity.\",\n      \"evidence\": \"In vitro reconstitution with purified proteins, EM visualization of filament disruption, D-loop assays, mouse knockout HR reporter\",\n      \"pmids\": [\"18003859\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of RAD51 interaction not yet mapped\", \"Whether RECQL5 acts as a translocase on ssDNA or uses a different mechanism was unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Discovery that RECQL5 is the only human RecQ helicase that directly associates with RNAPII revealed an unexpected second functional axis—transcription regulation—distinct from its recombination role.\",\n      \"evidence\": \"Targeted proteomics of chromatin-associated factors; direct interaction reconstituted with purified RECQL5 and RPB1\",\n      \"pmids\": [\"18562274\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Domain mediating Pol II interaction not yet mapped\", \"Functional consequence of the interaction unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Two parallel discoveries defined RECQL5's interactions at DNA damage sites: it constitutively associates with the MRN complex (inhibiting MRE11 exonuclease) and it directly inhibits RNAPII transcription initiation and elongation independent of helicase activity.\",\n      \"evidence\": \"Co-IP with MRN components, in vitro exonuclease inhibition, laser-induced DSB recruitment (PMID:19270065); reconstituted in vitro transcription with purified GTFs and RNAPII, helicase-dead mutant (PMID:19570979)\",\n      \"pmids\": [\"19270065\", \"19570979\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of MRN interaction not determined\", \"How helicase-independent transcription inhibition is achieved mechanistically was unclear\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Mapping of the SRI and KIX domains as dual RNAPII-binding modules, and the RAD51-interaction domain as the anti-recombinase interface, established the modular domain architecture underlying RECQL5's bifunctional activities.\",\n      \"evidence\": \"SRI domain binding to Ser2,5-phospho CTD by ChIP and in vitro binding (PMID:20705653); KIX domain binding Pol IIa/IIo with mutagenesis and SCE assays (PMID:20231364); RAD51-interaction domain point mutants disrupting filament displacement (PMID:20348101)\",\n      \"pmids\": [\"20705653\", \"20231364\", \"20348101\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-resolution structures of these domain–partner complexes not yet available\", \"How KIX and SRI domains coordinate during transcription elongation not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Connecting RECQL5's SRI-mediated RNAPII association to genome stability showed that loss of RECQL5 causes RNAPII-dependent double-strand breaks, establishing transcription stress as the proximal cause of genomic instability in RECQL5-deficient cells.\",\n      \"evidence\": \"SRI domain mutants, ChIP for active RNAPII, γH2AX/DSB assays rescued by transcription inhibitors\",\n      \"pmids\": [\"21402780\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genomic locations of transcription-dependent breaks not mapped\", \"Whether R-loops mediate the breaks was not tested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Discovery that RECQL5 physically stimulates Topoisomerase IIα decatenation activity expanded its functional repertoire beyond recombination and transcription to chromosome topology maintenance during S-phase.\",\n      \"evidence\": \"Co-IP, in vitro decatenation stimulation assay, co-localization in S-phase, chromosome entanglement phenotype upon RECQL5 depletion\",\n      \"pmids\": [\"22013166\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of stimulation (conformational change vs. recruitment) not determined\", \"Whether this is independent of RECQL5 helicase activity not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identification of a BRC repeat variant in RECQL5 that mimics BRCA2's RAD51-binding motifs provided the structural rationale for how RECQL5 engages the RAD51 protomer to disrupt filaments, while WRN interaction studies and DSB recruitment mapping further contextualized RECQL5's role at replication and damage sites.\",\n      \"evidence\": \"BRCv motif mutagenesis with D-loop, SCE, and binding assays (PMID:22645136); WRN co-IP and helicase stimulation assay, synthetic lethality (PMID:23180761); domain deletion live imaging at laser DSBs (PMID:22633600)\",\n      \"pmids\": [\"22645136\", \"23180761\", \"22633600\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Crystal structure of BRCv-RAD51 interface not solved\", \"Whether WRN stimulation is direct or mediated through substrate remodeling unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The first cryo-EM structure of RECQL5 bound to elongating Pol II revealed that its helicase domain sterically blocks the downstream DNA channel while its KIX domain competes with TFIIS, providing the atomic-level explanation for transcription inhibition and crossover suppression via non-crossover HR channeling.\",\n      \"evidence\": \"Cryo-EM of Pol II–RECQL5, KIX crystal structure, TFIIS competition assay (PMID:23748380); in vitro strand annealing showing RECQL5 counteracts RAD51 inhibition of RAD52-mediated annealing (PMID:24319145)\",\n      \"pmids\": [\"23748380\", \"24319145\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Resolution insufficient to define brake helix contacts\", \"How RECQL5 switches between transcription-inhibitory and HR-regulatory modes not addressed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Genome-wide RNAPII profiling upon RECQL5 depletion demonstrated that RECQL5 acts as a global transcription elongation rate regulator, with its loss causing increased elongation speed coupled with elevated stalling, and chromosomal breaks mapping to actively transcribed genes and fragile sites.\",\n      \"evidence\": \"Genome-wide RNAPII ChIP-seq, copy number analysis, RECQL5 depletion and overexpression showing reciprocal effects\",\n      \"pmids\": [\"24836610\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct mechanism linking faster elongation to increased stalling not resolved\", \"Whether RECQL5 acts at all genes or a subset preferentially was not fully distinguished\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Discovery that RECQL5 promotes TOP1 SUMOylation via the PIAS1-SRSF1 complex, enabling TOP1 to associate with active RNAPII and reduce R-loops, connected RECQL5's transcription role to co-transcriptional RNA processing and topological stress management.\",\n      \"evidence\": \"SUMOylation assays, K391/K436 mutagenesis, R-loop measurement, topoisomerase activity assays, chromatin fractionation\",\n      \"pmids\": [\"25851487\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether RECQL5's helicase activity contributes to this function not tested\", \"How RECQL5 facilitates PIAS1-TOP1 interaction structurally is unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Establishing that RECQL5 operates at replication-transcription collision sites—associating with both RNAPI/RNAPII complexes in replication foci and promoting PCNA ubiquitination—linked its transcription and replication functions mechanistically.\",\n      \"evidence\": \"Co-IP, PLA, ChIP, PCNA ubiquitination assay, DNA fiber analysis in RECQL5-depleted cells\",\n      \"pmids\": [\"27502483\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct structural basis of PCNA interaction not mapped\", \"Whether PCNA ubiquitination function is separable from RAD51 displacement not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstration that CDK1-phosphorylated RECQL5 associates with common fragile sites in early mitosis to remove RAD51 filaments and enable MUS81-dependent mitotic DNA synthesis explained how RECQL5 prevents under-replicated DNA from causing mitotic errors, while crystal structures of the helicase core in open/closed conformations defined the mechanochemical cycle.\",\n      \"evidence\": \"ChIP at CFSs, S727A phosphomutant, in vitro 3′-flap cleavage with RAD51 ± RECQL5 (PMID:28575661); X-ray crystallography, SAXS, ATPase/helicase assays (PMID:28100692)\",\n      \"pmids\": [\"28575661\", \"28100692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether phosphorylation at S727 affects other RECQL5 interactions not examined\", \"Structure of full-length RECQL5 including KIX/SRI domains not determined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Single-molecule imaging revealed RECQL5 as an ATP-dependent ssDNA translocase that dismantles RAD51 filaments through motor activity on the DNA lattice, while genetic epistasis established that RECQL5-dependent SDSA and ATRX-dependent HR represent competing DSB repair pathways governed by PCNA interaction.\",\n      \"evidence\": \"Single-molecule TIRF microscopy with RECQL5-F666A and RAD51-K133R mutants (PMID:33332547); epistasis with ATRX/BLM/MUS81/GEN1 knockouts and PCNA mutants (PMID:33431668)\",\n      \"pmids\": [\"33332547\", \"33431668\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PCNA interaction governs pathway choice mechanistically is unclear\", \"Whether RECQL5 translocase activity contributes to transcription regulation not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"High-resolution cryo-EM structures of RECQL5 on stalled Pol II elongation complexes identified the brake helix as the key structural element controlling translocation, showed nucleotide-dependent conformational switching that can restart paused Pol II, and revealed that the TCR complex competes with RECQL5 for Pol II engagement; separately, RECQL5 was shown to restrict RAD51-mediated fork reversal independently of its RNAPII interaction, and to function in pre-rRNA processing in the nucleolus.\",\n      \"evidence\": \"Cryo-EM in nucleotide-free and bound states (PMID:40624164, PMID:40624163); DNA fiber assays with fork remodeler co-depletions and domain-separation mutants (PMID:41099703); nucleolar localization, dsRNA unwinding, Northern blots for pre-rRNA (PMID:40823811)\",\n      \"pmids\": [\"40624164\", \"40624163\", \"41099703\", \"40823811\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length RECQL5 structure including all regulatory domains on Pol II not yet resolved\", \"Mechanism of nucleolar pre-rRNA processing function requires reconstitution\", \"Whether condensate formation is physiologically relevant awaits in vivo validation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major unresolved questions include: how RECQL5 switches between its separable transcription-regulatory and recombination/replication functions in vivo; the structural basis of RECQL5 engagement with PCNA, MRN, and Topo IIα; and whether RECQL5's nucleolar rRNA processing role is mechanistically linked to its genome maintenance functions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No in vivo structural data for full-length RECQL5 in complex with any partner\", \"Regulation of RECQL5 by post-translational modifications beyond S727 phosphorylation largely unexplored\", \"Pathological consequences of RECQL5 loss in human disease not established through genetic studies\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [0, 18, 19]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [18, 19, 25]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [33]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [33]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 19]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 14, 30, 31]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 7, 11, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [1, 22]},\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [21, 33]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [5, 14, 17]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 7, 11, 13, 17, 20]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 5, 6, 9, 12, 14, 30, 31]},\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [16, 26, 32]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [33]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [10, 17]}\n    ],\n    \"complexes\": [\n      \"RNAPII elongation complex\",\n      \"MRN complex (associated)\"\n    ],\n    \"partners\": [\n      \"RAD51\",\n      \"RPB1\",\n      \"MRE11\",\n      \"NBS1\",\n      \"TOP2A\",\n      \"MUS81\",\n      \"WRN\",\n      \"PCNA\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}