Rqh1 (also known as rad12, hus2 and rec9) is the single RecQ-family ATP-dependent 3'-5' DNA helicase of Schizosaccharomyces pombe, orthologous to Saccharomyces cerevisiae Sgs1 and to the human RecQ helicases BLM, WRN and RECQL4. The 1328-residue protein contains a central SF2 helicase core (Walker-A ATP-binding motif and DEAH box), a RecQ-specific RQC/zinc-binding region and a C-terminal HRDC domain. It couples ATP hydrolysis to 3'-to-5' unwinding of duplex DNA (EC 5.6.2.4) and functions chiefly in the nucleus, including nuclear chromosomes, the nucleolus, replication forks and sites of DNA double-strand breaks. Rqh1 forms a high-molecular-weight complex with topoisomerase III (Top3), binding Top3 through its N-terminal region; this RecQ-Top3 complex maintains genome stability by suppressing inappropriate and hyper-recombination, by processing stalled and collapsed replication forks so that they restart without generating one-sided breaks and deletions, by dissolving/disassembling recombination intermediates such as D-loops and double Holliday junctions, and by contributing to homologous-recombination repair of double-strand breaks. Rqh1 also acts in the S-phase DNA-damage checkpoint (replication slowing) and in maintenance of the ribosomal DNA repeats and faithful chromosome segregation. Loss of Rqh1 causes hydroxyurea and UV sensitivity, elevated recombination and chromosome loss, and aberrant mitosis.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | REMOVE | Summary: Phylogenetic (IBA) propagation of cytoplasmic localization across the RecQ family. Rqh1 is a DNA helicase that acts on nuclear chromosomal DNA; all experimental S. pombe data localize it to the nucleus, nuclear chromosome, nucleolus, replication forks and DSB sites. There is no experimental support for a cytoplasmic site of action, so this generic IBA term is an over-annotation for this gene. Reason: Contradicted by experimental localization; Rqh1 acts in the nucleus, not the cytoplasm. The IBA cytoplasm term derives from family-wide propagation and is not supported for this nuclear DNA helicase. Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE COMPARTMENT OR COMPLEX MISMATCH Sources checked: PANTHER:PTN000344873 · RecQ-family ancestral node SUPPORTS SOURCE BUT NOT TARGET Cytoplasmic localization is supported in sibling RecQ subfamilies, but the Rqh1/BLM lineage is experimentally nuclear and lacks evidence for cytoplasmic activity. Supporting Evidence: PMID:12724426 Rqh1 localized to the nucleus throughout the cell cycle. |
| GO:0006260 DNA replication | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Rqh1 acts at DNA replication forks, processing stalled and collapsed forks to allow recovery and restart. The broad term DNA replication is acceptable but the more specific replication-fork processing terms (annotated separately) better capture its role. Reason: Generic phylogenetic term; Rqh1's replication-associated role is real but more precisely captured by replication fork processing terms. Retained as non-core to avoid implying a core replicative-helicase function. Supporting Evidence: PMID:15889146 These data indicate that Rqh1 acts to prevent blocked replication forks from collapsing and thereby inducing deletion events. |
| GO:0005634 nucleus | IBA GO_REF:0000033 | ACCEPT | Summary: Nuclear localization is strongly supported experimentally for Rqh1 and is consistent with its function as a chromosomal DNA helicase. Reason: Corroborated by experimental nuclear localization in S. pombe. Supporting Evidence: PMID:12724426 Rqh1 localized to the nucleus throughout the cell cycle. |
| GO:0005694 chromosome | IBA GO_REF:0000033 | ACCEPT | Summary: Rqh1 acts on chromosomal DNA; experimental data localize it to nuclear chromosomes. The IBA chromosome term is consistent with the more specific experimental nuclear chromosome annotation. Reason: Consistent with experimental nuclear chromosome localization (IDA, PMID:12724426). Supporting Evidence: PMID:12724426 Rqh1-dependent fluorescence overlapped with the DNA but was predominantly nucleolar. |
| GO:0000166 nucleotide binding | IEA GO_REF:0000002 | MODIFY | Summary: Generic InterPro-derived term. Rqh1 binds and hydrolyzes ATP, so it is a nucleotide-binding protein, but the specific term ATP binding (also annotated) is far more informative and should be preferred. Reason: Too general; ATP binding is the specific, experimentally supported MF for this RecQ helicase and is already present. Proposed replacements: ATP binding Supporting Evidence: PMID:12478586 Here we show that, like other RecQ family members, the Rqh1p protein displays 3' to 5' DNA helicase activity. |
| GO:0000724 double-strand break repair via homologous recombination | IEA GO_REF:0000117 | ACCEPT | Summary: Rqh1 participates in homologous-recombination repair of double-strand breaks (e.g. in G2 after UV/IR), acting downstream of Rad51/Rhp51 to process recombination intermediates. This IEA duplicates the experimentally supported IMP/IGI annotations. Reason: Corroborated by experimental IMP/IGI annotations to the same term in S. pombe. Supporting Evidence: PMID:12724426 Our data provide evidence that Rqh1 functions after Rad51 focus formation during DNA repair. |
| GO:0000729 DNA double-strand break processing | IEA GO_REF:0000117 | ACCEPT | Summary: Rqh1 (the Sgs1 ortholog) contributes to long-range end resection at DSBs, though in fission yeast this is a minor role with Exo1 dominant. This IEA duplicates the experimentally supported IMP annotation. Reason: Corroborated by experimental IMP annotation (PMID:21931565). Supporting Evidence: PMID:21931565 Exo1 is largely responsible for extended resection up to 3.1 kb from a DSB, with an activity dependent on Rqh1 (Sgs1) DNA helicase having a minor role. |
| GO:0003676 nucleic acid binding | IEA GO_REF:0000002 | MODIFY | Summary: Very general InterPro term. Rqh1 binds DNA specifically; the DNA binding term (also annotated) is the appropriate, more informative MF. Reason: Too general; DNA binding is the specific supported molecular function. Proposed replacements: DNA binding Supporting Evidence: PMID:15702347 The Schizosaccharomyces pombe rqh1+ gene encodes a member of the RecQ DNA helicase family. |
| GO:0003677 DNA binding | IEA GO_REF:0000117 | ACCEPT | Summary: Rqh1 is a DNA helicase that binds and translocates on DNA. DNA binding is a well-supported molecular function. Reason: Consistent with helicase activity and the TAS DNA-binding annotation. Supporting Evidence: PMID:12478586 Here we show that, like other RecQ family members, the Rqh1p protein displays 3' to 5' DNA helicase activity. |
| GO:0004386 helicase activity | IEA GO_REF:0000002 | MODIFY | Summary: Rqh1 is a helicase, but the experimentally demonstrated specific activity is ATP-dependent 3'-5' DNA helicase activity. The generic helicase term should be refined to the specific child term. Reason: Too general; biochemical data establish 3'-5' DNA helicase activity (GO:0043138), which is already annotated experimentally. Proposed replacements: 3'-5' DNA helicase activity Supporting Evidence: PMID:12478586 Here we show that, like other RecQ family members, the Rqh1p protein displays 3' to 5' DNA helicase activity. |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: Rqh1 contains a Walker-A ATP-binding motif and couples ATP binding/ hydrolysis to DNA unwinding; ATP binding is a core molecular function. Reason: Supported by the conserved ATP-binding motif and the demonstrated ATP-dependent helicase activity. Supporting Evidence: PMID:12724426 We show that Rqh1, the single Schizosaccharomyces pombe homologue, is a 3'-to-5' helicase and exists with Top3 in a high-molecular-weight complex. |
| GO:0005634 nucleus | IEA GO_REF:0000120 | ACCEPT | Summary: Duplicate nuclear-localization annotation (UniProt automatic). Supported by the experimental EXP/IDA nuclear localization for Rqh1. Reason: Corroborated by the experimental nuclear-localization annotations for Rqh1. Supporting Evidence: PMID:12724426 Rqh1 localized to the nucleus throughout the cell cycle. |
| GO:0006260 DNA replication | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro-derived duplicate of the DNA replication annotation. Rqh1 acts at replication forks; the more specific fork-processing terms are preferred. Reason: Generic term; replication-associated role is better captured by replication fork processing terms. Supporting Evidence: PMID:15889146 These data indicate that Rqh1 acts to prevent blocked replication forks from collapsing and thereby inducing deletion events. |
| GO:0006281 DNA repair | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Rqh1 is required for DNA repair, especially recombination-mediated repair of UV/IR damage and processing of damaged replication forks. The general DNA repair term is correct but less informative than the specific recombination/fork-processing terms annotated elsewhere. Reason: Correct but general parent term; specific DSB-repair-via-HR and fork processing terms better represent the core function. Supporting Evidence: PMID:9372918 We show that Rqhl is involved in a DNA damage survival mechanism which prevents cell death when UV-induced DNA damage cannot be removed. |
| GO:0006310 DNA recombination | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Rqh1 is centrally involved in DNA recombination, principally as a negative regulator/anti-recombinase that suppresses inappropriate and hyper-recombination and dissolves recombination intermediates. The general term is correct; more specific child terms are annotated experimentally. Reason: Correct but general parent; specific terms (resolution of recombination intermediates, recombinational repair) capture the core role. Supporting Evidence: PMID:19037101 the helicase Rqh1, which are implicated in replication fork stability and the negative regulation of recombination. |
| GO:0006312 mitotic recombination | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: Rqh1 acts in mitotically dividing cells to control recombination at stalled forks and DSBs, and to process mitotic recombination intermediates. The term is appropriate; more specific child terms are annotated. Reason: Correct but general; resolution of mitotic recombination intermediates and mitotic recombination-dependent fork processing are the specific terms. Supporting Evidence: PMID:23093942 Rqh1 limits GCRs at collapsed forks by preventing inappropriate ectopic recombination during the process of fork recovery by recombination proteins. |
| GO:0016887 ATP hydrolysis activity | IEA GO_REF:0000116 | ACCEPT | Summary: Rqh1 is an ATP-dependent helicase (EC 5.6.2.4) that hydrolyzes ATP to power 3'-5' translocation; ATP hydrolysis is an intrinsic core activity. Reason: Supported by the ATP-dependent helicase mechanism and RHEA EC mapping. Supporting Evidence: PMID:12724426 We show that Rqh1, the single Schizosaccharomyces pombe homologue, is a 3'-to-5' helicase and exists with Top3 in a high-molecular-weight complex. |
| GO:0031422 RecQ family helicase-topoisomerase III complex | IEA GO_REF:0000117 | ACCEPT | Summary: Rqh1 forms a high-molecular-weight complex with topoisomerase III (Top3), the defining RecQ-Top3 complex. Well supported experimentally. Reason: Corroborated by experimental IDA/NAS annotations for the RecQ-Top3 complex. Supporting Evidence: PMID:12724426 We show that Rqh1, the single Schizosaccharomyces pombe homologue, is a 3'-to-5' helicase and exists with Top3 in a high-molecular-weight complex. |
| GO:0031573 mitotic intra-S DNA damage checkpoint signaling | IEA GO_REF:0000117 | ACCEPT | Summary: Rqh1 is required, in an epistatic pathway with Mus81 and Rhp51 downstream of Cds1, for slowing replication in response to S-phase DNA damage. This IEA duplicates the experimentally supported IMP annotations. Reason: Corroborated by experimental IMP annotations (PMID:19037101). Supporting Evidence: PMID:19037101 We have identified proteins downstream of Cds1 required for checkpoint-dependant slowing, including the structure-specific endonuclease Mus81 and the helicase Rqh1. |
| GO:0043138 3'-5' DNA helicase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Core molecular function: ATP-dependent 3'-5' DNA helicase activity, shown biochemically. This IEA matches the experimental IDA annotations. Reason: Corroborated by experimental IDA biochemical demonstration. Supporting Evidence: PMID:12478586 Here we show that, like other RecQ family members, the Rqh1p protein displays 3' to 5' DNA helicase activity. |
| GO:0031422 RecQ family helicase-topoisomerase III complex | NAS PMID:15702347 The N-terminal region of the Schizosaccharomyces pombe RecQ ... | ACCEPT | Summary: The N-terminal region of Rqh1 physically binds Top3, supporting membership in the RecQ-Top3 complex. Consistent with the IDA complex annotation. Reason: Supported by demonstrated physical Top3 binding via the Rqh1 N-terminus. Supporting Evidence: PMID:15702347 Topoisomerase III (Top3) binds to a site within the first 322 N-terminal amino acids of Rqh1 and that this binding correlates with Rqh1 function. |
| GO:0005634 nucleus | EXP PMID:12724426 Role for the fission yeast RecQ helicase in DNA repair in G2... | ACCEPT | Summary: Experimental (EXP) nuclear localization of Rqh1 in S. pombe. This is the primary, well-supported localization for the protein. Reason: Direct experimental evidence for nuclear localization. Supporting Evidence: PMID:12724426 Rqh1 localized to the nucleus throughout the cell cycle. |
| GO:0043007 maintenance of rDNA | IMP PMID:14528010 Slx1-Slx4 are subunits of a structure-specific endonuclease ... | ACCEPT | Summary: Deletion of Rqh1 causes contraction of the rDNA repeats, and rqh1 is synthetically lethal with the Slx1-Slx4 endonuclease, demonstrating a role in maintaining rDNA copy number at the replication fork barriers in the rDNA locus. Reason: Direct mutant-phenotype evidence for rDNA maintenance. Supporting Evidence: PMID:14528010 Deletion of Slx1 or Rqh1 RecQ-like DNA helicase provokes rDNA contraction, whereas simultaneous elimination of Slx1-Slx4 endonuclease and Rqh1 is lethal. |
| GO:1990426 mitotic recombination-dependent replication fork processing | IMP PMID:30667359 Factors affecting template switch recombination associated w... | ACCEPT | Summary: Rqh1, together with Fbh1 and Srs2, strongly suppresses template switching during recombination-restarted replication, a key aspect of processing restarted forks. Direct mutant evidence. Reason: Direct genetic evidence that Rqh1 suppresses template switching at restarted forks. Supporting Evidence: PMID:30667359 A further three conserved helicases (Fbh1, Rqh1 and Srs2) strongly suppress TS, but there is no change in TS frequency in cells lacking Fml1 or Mus81. |
| GO:0000729 DNA double-strand break processing | IMP PMID:21931565 Release of Ku and MRN from DNA ends by Mre11 nuclease activi... | ACCEPT | Summary: Rqh1 (Sgs1 ortholog) contributes to extended end resection at DSBs, supporting Exo1-dependent long-range resection, although it plays a minor role relative to Exo1 in fission yeast. Reason: Direct evidence for a (minor) role in DSB end resection/processing. Supporting Evidence: PMID:21931565 Exo1 is largely responsible for extended resection up to 3.1 kb from a DSB, with an activity dependent on Rqh1 (Sgs1) DNA helicase having a minor role. |
| GO:0000724 double-strand break repair via homologous recombination | IMP PMID:12023299 Cdc2-cyclin B kinase activity links Crb2 and Rqh1-topoisomer... | ACCEPT | Summary: Rqh1, in association with Top3, processes recombination intermediates during HR repair of radiation-induced DSBs in G2, acting after the assembly of Rhp51 (Rad51) foci. Core DSB-repair function. Reason: Direct mutant evidence for a role in HR repair of DSBs in G2. Supporting Evidence: PMID:12023299 low Cdc2-cyclin B activity prevents the proper regulation of topoisomerase III (Top3) function, disrupting a recombination step that occurs after the assembly of Rhp51 foci. |
| GO:0000724 double-strand break repair via homologous recombination | IGI PMID:12023299 Cdc2-cyclin B kinase activity links Crb2 and Rqh1-topoisomer... | ACCEPT | Summary: Genetic-interaction evidence (with crb2/rad50 partners) places Rqh1-Top3 in the HR pathway for repairing G2 DSBs, downstream of Rhp51 focus assembly. Consistent with the IMP annotation to the same term. Reason: Genetic-interaction evidence supports the HR DSB-repair role. Supporting Evidence: PMID:12023299 low Cdc2-cyclin B activity prevents the proper regulation of topoisomerase III (Top3) function, disrupting a recombination step that occurs after the assembly of Rhp51 foci. |
| GO:0005730 nucleolus | IDA PMID:12023299 Cdc2-cyclin B kinase activity links Crb2 and Rqh1-topoisomer... | ACCEPT | Summary: Rqh1 localizes to the nucleolus, consistent with its role in maintaining the rDNA repeats located there. Direct localization evidence. Reason: Direct experimental nucleolar localization, consistent with independently established rDNA maintenance. Supporting Evidence: PMID:12023299 Rqh1 relocalized from a predominantly nucleolar distribution to discrete foci in the chromatin compartment 1 h postirradiation |
| GO:0035861 site of double-strand break | IDA PMID:12023299 Cdc2-cyclin B kinase activity links Crb2 and Rqh1-topoisomer... | ACCEPT | Summary: Rqh1 is recruited to sites of DNA double-strand breaks, consistent with its role in HR repair downstream of Rhp51 focus formation. Reason: Direct damage-induced relocalization to chromatin foci, consistent with recruitment to DSB sites during HR repair. Supporting Evidence: PMID:12023299 Rqh1 relocalized from a predominantly nucleolar distribution to discrete foci in the chromatin compartment 1 h postirradiation |
| GO:0031573 mitotic intra-S DNA damage checkpoint signaling | IMP PMID:19037101 Mus81, Rhp51(Rad51), and Rqh1 form an epistatic pathway requ... | ACCEPT | Summary: Rqh1 functions in an epistatic pathway with Mus81 and Rhp51, downstream of the checkpoint kinase Cds1, that is required for slowing replication in response to S-phase DNA damage. Direct mutant evidence. Reason: Direct mutant evidence for a role in the intra-S DNA damage checkpoint (replication slowing). Supporting Evidence: PMID:19037101 We have identified proteins downstream of Cds1 required for checkpoint-dependant slowing, including the structure-specific endonuclease Mus81 and the helicase Rqh1. |
| GO:1990426 mitotic recombination-dependent replication fork processing | IDA PMID:25313826 The chromatin assembly factor 1 promotes Rad51-dependent tem... | ACCEPT | Summary: Rqh1 disassembles recombination D-loops formed during Rad51-dependent template switching at blocked forks; CAF-1 antagonizes this disassembly. Direct physical-assay evidence for fork-intermediate processing. Reason: Direct (physical assay) evidence that Rqh1 disassembles D-loops at restarted forks. Supporting Evidence: PMID:25313826 We establish that CAF-1 promotes template switch by counteracting D-loop disassembly by Rqh1. |
| GO:0070914 UV-damage excision repair | IMP PMID:7623848 An alternative eukaryotic DNA excision repair pathway. | MARK AS OVER ANNOTATED | Summary: This annotation derives from the rad12-502 allele, which was reported to lack the SPDE UV-dimer endonuclease activity of an alternative excision repair pathway. However, the same gene was subsequently shown to be the RecQ helicase rqh1/hus2, and a later study explicitly could not reproduce a UV-dimer endonuclease defect in rqh1 (rad12) mutants. The excision (SPDE) activity is not a property of the RecQ helicase, and Rqh1's true UV role is in recombination-based damage tolerance/bypass during S phase. This is best regarded as an over-annotation (historic misattribution of a distinct excision-repair endonuclease function to Rqh1). Reason: The SPDE/UV-dimer excision activity attributed to the rad12-502 strain is not a function of the RecQ helicase and was later refuted; Rqh1's UV role is in recombination/replication-bypass damage tolerance, not excision repair. Per the do-not-overrule rule this is downgraded rather than removed, as the rad12-502 phenotype is genuine even if mechanistically reassigned. Supporting Evidence: PMID:7623848 Here we report that the UV-sensitive S. pombe rad12-502 mutant lacks SPDE activity. PMID:9372918 in contrast with the reported literature, we do not find that rqh1 (rad12) mutant cells are defective in UV dimer endonuclease activity. |
| GO:1990426 mitotic recombination-dependent replication fork processing | IMP PMID:23093942 Recovery of arrested replication forks by homologous recombi... | ACCEPT | Summary: Rqh1 limits gross chromosomal rearrangements at collapsed forks by preventing inappropriate ectopic recombination during HR-mediated fork recovery. Direct mutant evidence for fork processing. Reason: Direct mutant evidence for Rqh1 in processing recombination-restarted forks. Supporting Evidence: PMID:23093942 Rqh1 limits GCRs at collapsed forks by preventing inappropriate ectopic recombination during the process of fork recovery by recombination proteins. |
| GO:0000228 nuclear chromosome | IDA PMID:12724426 Role for the fission yeast RecQ helicase in DNA repair in G2... | ACCEPT | Summary: Rqh1 localizes to and acts on nuclear chromosomes, consistent with its role as a chromosomal DNA helicase in DNA repair and recombination. Reason: Direct experimental nuclear-chromosome localization. Supporting Evidence: PMID:12724426 Rqh1-dependent fluorescence overlapped with the DNA but was predominantly nucleolar. |
| GO:0005730 nucleolus | IDA PMID:12724426 Role for the fission yeast RecQ helicase in DNA repair in G2... | ACCEPT | Summary: Nucleolar localization consistent with the role of the Rqh1-Top3 complex in maintaining rDNA repeat structure. Direct localization evidence. Reason: Direct experimental nucleolar localization, consistent with independently established rDNA maintenance. Supporting Evidence: PMID:12724426 Rqh1-dependent fluorescence overlapped with the DNA but was predominantly nucleolar. |
| GO:0006301 DNA damage tolerance | IMP PMID:12724426 Role for the fission yeast RecQ helicase in DNA repair in G2... | ACCEPT | Summary: Rqh1 is required for survival of UV-induced DNA damage that cannot be removed, operating in S phase as part of a damage-tolerance/bypass mechanism. Direct mutant evidence (rqh1 deletion is UV/HU sensitive). Reason: Direct mutant-phenotype evidence for a role in DNA damage tolerance. Supporting Evidence: PMID:9372918 We show that Rqhl is involved in a DNA damage survival mechanism which prevents cell death when UV-induced DNA damage cannot be removed. |
| GO:0043138 3'-5' DNA helicase activity | IDA PMID:12724426 Role for the fission yeast RecQ helicase in DNA repair in G2... | ACCEPT | Summary: Core molecular function. Rqh1 was directly shown to be a 3'-to-5' DNA helicase; T543I and K547A/R mutations abolish this activity. Reason: Direct biochemical demonstration of 3'-5' DNA helicase activity. Supporting Evidence: PMID:12724426 We show that Rqh1, the single Schizosaccharomyces pombe homologue, is a 3'-to-5' helicase and exists with Top3 in a high-molecular-weight complex. |
| GO:0031297 replication fork processing | IGI PMID:16303848 A role for the fission yeast Rqh1 helicase in chromosome seg... | ACCEPT | Summary: Rqh1 (the Top3-RecQ complex) processes aberrant chromosome structures arising from DNA replication, particularly at the rDNA replication fork barriers; rqh1 deletion causes anaphase delay and lagging rDNA. Reason: Genetic-interaction evidence (reb1 suppression) for fork processing at the rDNA locus. Supporting Evidence: PMID:16303848 These data are consistent with the function of the Top3-RecQ complex in maintenance of the rDNA structure by processing aberrant chromosome structures arising from DNA replication. |
| GO:0043007 maintenance of rDNA | IMP PMID:16303848 A role for the fission yeast Rqh1 helicase in chromosome seg... | ACCEPT | Summary: rqh1 deletion produces lagging chromosomal DNA especially at the rDNA locus and anaphase delay; relieving rDNA fork arrest (reb1 deletion) partially suppresses these phenotypes, supporting a role in rDNA maintenance via the Top3-RecQ complex. Reason: Direct mutant evidence for rDNA maintenance (also independently supported by PMID:14528010). Supporting Evidence: PMID:16303848 relieving replication fork arrest in the rDNA repeat by deletion of reb1+ partially suppresses rqh1delta phenotypes. |
| GO:0071140 resolution of mitotic recombination intermediates | IMP PMID:15889146 Replication fork blockage by RTS1 at an ectopic site promote... | ACCEPT | Summary: Rqh1 acts to prevent blocked replication forks from collapsing and generating one-sided DSBs and deletion events at the RTS1 fork barrier, consistent with resolving/dissolving recombination intermediates at stalled forks. Direct mutant evidence. Reason: Direct mutant evidence that Rqh1 resolves recombination intermediates at blocked forks. Supporting Evidence: PMID:15889146 In the absence of the RecQ family DNA helicase Rqh1, deletion events increase dramatically, which correlates with the detection of one-sided DNA double-strand breaks at or near RTS1. These data indicate that Rqh1 acts to prevent blocked replication forks from collapsing and thereby inducing deletion events. |
| GO:0000725 recombinational repair | IGI PMID:16135799 Role of the Schizosaccharomyces pombe F-Box DNA helicase in ... | ACCEPT | Summary: Rqh1 functions in processing recombination intermediates; the fbh1 F-box helicase is synthetically lethal with rqh1 (and srs2), with lethality suppressed by rhp57 deletion, indicating overlapping roles in resolving toxic Rhp51-dependent recombination intermediates. Reason: Genetic-interaction (synthetic lethality with fbh1) evidence for recombinational repair. Supporting Evidence: PMID:16135799 fbh1 is essential for viability in stationary-phase cells and in the absence of either Srs2 or Rqh1 DNA helicase. In each case, lethality is suppressed by deletion of the recombination gene rhp57. |
| GO:0006974 DNA damage response | IMP PMID:9372918 Role of Schizosaccharomyces pombe RecQ homolog, recombinatio... | KEEP AS NON CORE | Summary: Rqh1 operates during S phase as part of a DNA damage survival mechanism requiring the recombination machinery, the checkpoint rad genes and Cds1. The broad DNA damage response term is correct but general; specific checkpoint and recombination terms are annotated separately. Reason: Correct but general parent term; more specific checkpoint and damage-tolerance terms capture the core role. Supporting Evidence: PMID:9372918 Our data suggest that Rqh1 operates during S phase as part of a mechanism which prevents DNA damage causing cell lethality. |
| GO:0003677 DNA binding | TAS PMID:15702347 The N-terminal region of the Schizosaccharomyces pombe RecQ ... | ACCEPT | Summary: DNA binding is well supported for this RecQ helicase that binds and translocates on DNA. Reason: Consistent with the demonstrated DNA helicase activity. Supporting Evidence: PMID:15702347 The Schizosaccharomyces pombe rqh1+ gene encodes a member of the RecQ DNA helicase family. |
| GO:0031422 RecQ family helicase-topoisomerase III complex | IDA PMID:12724426 Role for the fission yeast RecQ helicase in DNA repair in G2... | ACCEPT | Summary: Direct evidence that Rqh1 exists with Top3 in a high-molecular-weight complex (the RecQ-Top3 complex). Core cellular-component assignment. Reason: Direct experimental evidence for the Rqh1-Top3 complex. Supporting Evidence: PMID:12724426 We show that Rqh1, the single Schizosaccharomyces pombe homologue, is a 3'-to-5' helicase and exists with Top3 in a high-molecular-weight complex. |
| GO:0043138 3'-5' DNA helicase activity | IDA PMID:12478586 Helicase activity is only partially required for Schizosacch... | ACCEPT | Summary: Independent biochemical demonstration that Rqh1p displays 3'-5' DNA helicase activity. Core molecular function. Reason: Direct biochemical demonstration of 3'-5' DNA helicase activity. Supporting Evidence: PMID:12478586 Here we show that, like other RecQ family members, the Rqh1p protein displays 3' to 5' DNA helicase activity. |
| GO:0043596 nuclear replication fork | IC PMID:12724426 Role for the fission yeast RecQ helicase in DNA repair in G2... | ACCEPT | Summary: Curator-inferred (IC, from the RecQ-Top3 complex annotation) localization to the nuclear replication fork. Consistent with Rqh1's well-documented action at stalled/collapsed replication forks. Reason: Inference is consistent with extensive evidence that Rqh1 acts at replication forks to prevent collapse and process restarted forks. Supporting Evidence: PMID:15889146 These data indicate that Rqh1 acts to prevent blocked replication forks from collapsing and thereby inducing deletion events. |
| GO:0043138 3'-5' DNA helicase activity | IBA GO_REF:0000033 | ACCEPT | Summary: The PAINT assertion places conserved 3'-5' DNA helicase activity at the RecQ-family ancestral node; Rqh1 itself is among the experimental descendants and purified Rqh1 directly displays this activity. Reason: Core molecular function, independently demonstrated for S. pombe Rqh1; the target's presence among the PAINT descendants is experimental grounding, not circularity. Supporting Evidence: PMID:12478586 Here we show that, like other RecQ family members, the Rqh1p protein displays 3' to 5' DNA helicase activity. |
| GO:0000724 double-strand break repair via homologous recombination | IBA GO_REF:0000033 | ACCEPT | Summary: The PAINT assertion places homologous-recombination repair of double-strand breaks at the BLM/Sgs1/Rqh1 lineage; Rqh1 has direct genetic evidence for this process and acts after Rad51 focus formation. Reason: Conserved core genome-maintenance role, corroborated by S. pombe IMP and IGI annotations to the same term. Supporting Evidence: PMID:12724426 Our data provide evidence that Rqh1 functions after Rad51 focus formation during DNA repair. |
| GO:0009378 four-way junction helicase activity | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: The PAINT assertion captures the conserved ability of RecQ helicases to unwind branched four-way recombination intermediates. Rqh1 belongs to the BLM/Sgs1 subfamily within the asserted node and experimentally disassembles recombination D-loops, but no direct purified-Rqh1 four-way-junction assay was identified. Reason: Appropriate conserved substrate specialization of the RecQ helicase; PAINT places the activity at a node supported by four characterized seed lineages, with no evidence of loss in the Rqh1 lineage. It is retained as non-core because no direct purified-Rqh1 experiment on a four-way substrate was identified. Supporting Evidence: PMID:25313826 We establish that CAF-1 promotes template switch by counteracting D-loop disassembly by Rqh1. |
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Download this section (compressed HTML)Q: Is the partial dispensability of Rqh1 helicase activity for S-phase recovery explained by a structural/scaffolding role of Rqh1 in the Top3 complex, or by redundancy with other helicases (Fbh1, Srs2, Pfh1)?
Q: Does the fission-yeast Rqh1-Top3 complex include an Rmi1/RMI ortholog, and how does its composition compare to the human BLM-Top3a-RMI1-RMI2 dissolvasome?
Q: To what extent does Rqh1 perform canonical double-Holliday-junction dissolution versus D-loop disassembly/anti-recombinase activity in vivo?
Experiment: Reconstitute the Rqh1-Top3 (and candidate Rmi1) complex and test double Holliday junction dissolution and D-loop disassembly in vitro, comparing wild-type Rqh1 with the helicase-dead K547A and Top3-binding N-terminal deletion variants.
Experiment: Use chromatin immunoprecipitation / live-cell imaging of tagged Rqh1 to map its genome-wide binding at stalled forks, the rDNA fork barriers and induced DSBs, and to define the kinetics relative to Rhp51 and Top3 foci.
Experiment: Systematically separate Rqh1 functions using separation-of-function alleles (helicase-dead, HRDC-domain mutants, Top3-binding mutants) and quantify template switching, rDNA stability, end resection and checkpoint-dependent replication slowing for each.
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