Rad21 is the alpha-kleisin subunit of the mitotic cohesin complex of fission yeast and the ortholog of budding yeast Scc1/Mcd1 and human RAD21. It is an essential 628-residue protein whose N- and C-terminal domains bind the ATPase head domains of the SMC subunits Psm3 (Smc3) and Psm1 (Smc1) respectively, thereby bridging them and, together with the HEAT-repeat subunit Psc3 (Scc3), closing the tripartite cohesin ring. This ring topologically entraps DNA and, after S phase, two sister DNA molecules, establishing and maintaining sister chromatid cohesion from replication until anaphase. The complex is loaded onto chromatin by the Mis4 (Scc2)/Ssl3 (Scc4) loader in an ATP-hydrolysis-dependent reaction, is stabilized during S phase by the acetyltransferase Eso1 (Eco1), and is dynamically removed by the Wapl (Wpl1) unloading activity. At the metaphase-to-anaphase transition the protease separase (Cut1), activated by destruction of its inhibitor securin (Cut2), cleaves a small but essential fraction of Rad21, opening the ring and allowing sister chromatids to segregate. Rad21 is hyperphosphorylated during S and G2 phases and is a cell-cycle-regulated nuclear phosphoprotein. Rad21-containing cohesin is enriched across broad centromeric/pericentromeric heterochromatin and subtelomeric regions, contributes to chromatin loop formation, and functions in DNA double-strand break repair. Rad21 was originally identified through a radiation-sensitive, double-strand-break-repair-deficient mutant, and both its repair and cohesion roles are well established.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0030892 mitotic cohesin complex | IBA GO_REF:0000033 | ACCEPT | Summary: Rad21 is the alpha-kleisin subunit of the mitotic cohesin complex, a core and well-established part of its identity. The phylogenetic inference is fully consistent with direct experimental evidence in fission yeast. Reason: Core cellular component. Rad21 forms a stable complex with the SMC subunits Psm1 and Psm3 by immunoprecipitation, confirming membership in the mitotic cohesin complex. Supporting Evidence: PMID:11069892 Immunoprecipitation demonstrates stable complex formation of Rad21 with Psm1 and Psm3 but not with Psc3. |
| GO:0007064 mitotic sister chromatid cohesion | IBA GO_REF:0000033 | ACCEPT | Summary: Mitotic sister chromatid cohesion is the central biological process of Rad21. The phylogenetic inference matches direct experimental evidence: cohesin-subunit mutants show precocious sister chromatid separation. Reason: Core biological process, corroborated by multiple direct/mutant studies in S. pombe. Supporting Evidence: PMID:19948483 Based on previous data suggesting that centromeric cohesion is required to prevent merotelic attachment (Gregan et al., 2007), we characterized the segregation defects seen in cells mutated for the Rad21 cohesin subunit at the permissive temperature of 25Β°C. |
| GO:1990414 replication-born double-strand break repair via sister chromatid exchange | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Cohesin promotes recombinational repair of replication-associated double-strand breaks by holding the sister chromatid available as a repair template. This IBA term is a specific, mechanistically plausible elaboration of cohesin's repair role, consistent with Rad21's documented role in DSB repair, but the specific sister-chromatid-exchange sub-process has not been directly demonstrated for S. pombe rad21 in our cached evidence. Reason: Plausible phylogenetically inferred repair role; supported in general terms by Rad21's experimental DSB-repair phenotype, but the precise SCE sub-process is not directly assayed here. Retained as a non-core repair function. Supporting Evidence: PMID:1480481 The plasmid-borne gene completely reestablished the DNA dsb repair pathway. |
| GO:0003682 chromatin binding | IBA GO_REF:0000033 | ACCEPT | Summary: Rad21/cohesin associates with chromatin and is loaded onto chromosomes by Mis4. Chromatin binding is supported directly by ChIP and localization data, so the phylogenetic inference is well founded. Reason: Supported by direct chromatin association and loading evidence; an appropriate molecular function for a chromatin-bound structural subunit. Supporting Evidence: PMID:11069892 Mis4, another sister chromatid cohesion protein, plays an essential role for loading Rad21 on chromatin. |
| GO:0000775 chromosome, centromeric region | IEA GO_REF:0000044 | ACCEPT | Summary: Cohesin (and Rad21) is enriched at broad centromeric regions in fission yeast. This UniProt subcellular-location-derived IEA is consistent with direct evidence and with the more specific IDA term for the condensed chromosome centromeric region. Reason: Centromeric/pericentromeric localization is directly demonstrated by ChIP and immunolocalization. Supporting Evidence: PMID:11069892 Chromatin immunoprecipitation shows that cohesin subunits are enriched in broad centromere regions and that the level of centromere-associated Rad21 did not change from metaphase to anaphase, very different from budding yeast. |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: Rad21 is a nuclear protein throughout the cell cycle, with an NLS in its C-terminal third. The IEA from UniProt subcellular location is well supported by direct experimental evidence. Reason: Nuclear localization is directly and repeatedly demonstrated. Supporting Evidence: PMID:7706319 The Rad21 protein is nuclear during the cell cycle. |
| GO:0007062 sister chromatid cohesion | IEA GO_REF:0000002 | MODIFY | Summary: This InterPro2GO IEA assigns the general parent term sister chromatid cohesion. It is correct but less specific than the mitotic sister chromatid cohesion term that is directly supported for Rad21. Reason: The general term is subsumed by the more specific, directly supported mitotic sister chromatid cohesion term. Proposed replacements: mitotic sister chromatid cohesion Supporting Evidence: PMID:11069892 Precocious sister chromatid separation was observed in cohesin subunit mutants, strongly suggesting that fission yeast cohesin was also required to establish sister chromatid cohesion. |
| GO:0008278 cohesin complex | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO assigns the general cohesin complex term. It is correct but less specific than the directly supported mitotic cohesin complex term that applies to fission yeast Rad21. Reason: Subsumed by the more specific mitotic cohesin complex term, which is directly supported. Proposed replacements: mitotic cohesin complex Supporting Evidence: PMID:11069892 Immunoprecipitation demonstrates stable complex formation of Rad21 with Psm1 and Psm3 but not with Psc3. |
| GO:0005634 nucleus | NAS PMID:11069892 Characterization of fission yeast cohesin: essential anaphas... | ACCEPT | Summary: Nuclear localization is correct and well supported. This is a ComplexPortal NAS entry duplicating the better-supported IDA nucleus annotations. Reason: Nuclear localization is directly demonstrated. Supporting Evidence: PMID:11069892 the same nuclear localization of Rad21 was observed during the cell cycle by regular and detergent-treated fluorescence microscopy |
| GO:0030892 mitotic cohesin complex | IPI PMID:11069892 Characterization of fission yeast cohesin: essential anaphas... | ACCEPT | Summary: ComplexPortal IPI annotation for membership of the mitotic cohesin complex, based on the demonstrated physical complex with Psm1/Psm3. Correct core component. Reason: Direct physical-interaction evidence for cohesin complex membership. Supporting Evidence: PMID:11069892 Immunoprecipitation demonstrates stable complex formation of Rad21 with Psm1 and Psm3 but not with Psc3. |
| GO:0034087 establishment of mitotic sister chromatid cohesion | NAS PMID:11069892 Characterization of fission yeast cohesin: essential anaphas... | ACCEPT | Summary: Rad21/cohesin establishes sister chromatid cohesion during S phase; loss of viability in rad21-K1 occurs in S phase, consistent with an establishment role. This is a specific, accurate sub-process of cohesion. Reason: Supported by S-phase loss-of-viability/precocious-separation phenotypes indicating a role in establishing cohesion. Supporting Evidence: PMID:11069892 As ts rad21-K1 mutant cells lost viability during the S phase, sister cohesion was likely to be established by the complex during the S phase. |
| GO:0005730 nucleolus | IDA PMID:12748297 Cohesins determine the attachment manner of kinetochores to ... | UNDECIDED | Summary: PomBase reports nucleolar localization of Rad21, but the accessible text of the cited paper does not expose the evidence for this precise site. If verified, the nucleolus would be a peripheral, non-core localization relative to centromeric cohesion. Reason: The cached text for the original experimental reference is focused on meiotic kinetochore attachment and does not verify the nucleolar localization claim. Because this is an experimental curator annotation, it is retained but marked undecided rather than removed. |
| GO:0045143 homologous chromosome segregation | IMP PMID:12748297 Cohesins determine the attachment manner of kinetochores to ... | KEEP AS NON CORE | Summary: This reflects the meiosis-I behavior in which substitutive Rad21 relocates to centromeres in the absence of Rec8 and directs bipolar (equational) attachment. It is a genuine but non-canonical, meiotic role for Rad21 rather than its core mitotic function. Reason: Experimentally supported meiotic role of substitutive Rad21; non-core relative to its mitotic cohesion function. Supporting Evidence: PMID:12748297 the equational segregation at meiosis I depends on substitutive Rad21, which relocates to the centromeres if Rec8 is absent. |
| GO:0005634 nucleus | IDA PMID:11069892 Characterization of fission yeast cohesin: essential anaphas... | ACCEPT | Summary: Direct microscopy shows Rad21 is nuclear throughout the cell cycle. Correct core localization. Reason: Direct immunofluorescence evidence of nuclear localization. Supporting Evidence: PMID:11069892 the same nuclear localization of Rad21 was observed during the cell cycle by regular and detergent-treated fluorescence microscopy |
| GO:0007064 mitotic sister chromatid cohesion | IMP PMID:29358048 Establishment of DNA-DNA Interactions by the Cohesin Ring. | ACCEPT | Summary: Reconstituted fission yeast cohesin (including Rad21) establishes DNA-DNA interactions, the biochemical basis of sister chromatid cohesion. Mitotic sister chromatid cohesion is the core process of Rad21. Reason: Core process supported by reconstitution of cohesin-mediated DNA-DNA tethering. Supporting Evidence: PMID:29358048 Here, we demonstrate DNA-DNA tethering by the purified fission yeast cohesin complex. |
| GO:0007064 mitotic sister chromatid cohesion | IMP PMID:19948483 Ase1/Prc1-dependent spindle elongation corrects merotely dur... | ACCEPT | Summary: Rad21 is used here as a cohesion/separation marker in a study of anaphase spindle elongation and merotely correction; the cohesion role is genuine and consistent with the core function. Reason: Core process. Annotation is consistent with rad21's established cohesion function; the abstract foregrounds Ase1/Prc1 but the full text assays rad21 cohesion, so the curator annotation is retained. Supporting Evidence: PMID:19948483 Based on previous data suggesting that centromeric cohesion is required to prevent merotelic attachment (Gregan et al., 2007), we characterized the segregation defects seen in cells mutated for the Rad21 cohesin subunit at the permissive temperature of 25Β°C. |
| GO:0140588 chromatin looping | IDA PMID:34309513 A Brownian ratchet model for DNA loop extrusion by the cohes... | ACCEPT | Summary: Fission yeast cohesin extrudes DNA loops, forming chromatin domains. Chromatin looping is a directly demonstrated activity of the purified Rad21-containing cohesin complex, distinct from sister chromatid cohesion. Reason: Supported by single-molecule/biophysical demonstration of cohesin-mediated DNA loop extrusion. Supporting Evidence: PMID:34309513 cohesin extrudes DNA loops, thought to reflect chromatin domain formation. |
| GO:0061776 ATP-dependent topological DNA co-entrapment activity | EXP PMID:33176147 DNA Binding by the Mis4(Scc2) Loader Promotes Topological DN... | ACCEPT | Summary: The cohesin ring, with Rad21 closing it, topologically entraps DNA in an ATP-hydrolysis-dependent reaction promoted by the Mis4 loader. This is a well-defined molecular activity of the complex to which Rad21 contributes, and the contributes_to qualifier is appropriate for a ring-level activity. Reason: Directly supported biochemical activity of the cohesin ring containing Rad21; contributes_to correctly attributes a complex-level function. Supporting Evidence: PMID:33176147 cohesion, is a ring-shaped multi-subunit ATPase that topologically embraces DNA. PMID:33176147 topological DNA entrapment by cohesin through its DNA binding activity |
| GO:1990342 heterochromatin island | IDA PMID:22144463 RNA elimination machinery targeting meiotic mRNAs promotes f... | KEEP AS NON CORE | Summary: Direct ChIP evidence shows Rad21 enrichment at facultative heterochromatin islands over meiotic genes in vegetatively growing cells. This is a genuine but specialized, non-core localization. Reason: Direct ChIP evidence in PMID:22144463 supports the base cellular-component annotation. It is retained as non-core relative to Rad21's central chromatin/cohesin localization. The OpenScientist report separately flags the PomBase exists_during meiotic-cell-cycle extension for curator review, because the reported ChIP used log-growing vegetative cells. Supporting Evidence: PMID:22144463 the cohesin sub unit Rad21 enriched at meiotic heterochromatin islands (fig. S2). |
| GO:0007064 mitotic sister chromatid cohesion | EXP PMID:29735656 Suppressor mutation analysis combined with 3D modeling expla... | ACCEPT | Summary: Suppressor and 3D-modeling analysis of the Psm1-Rad21 and Psm3-Rad21 interfaces explains cohesin's capacity to hold and release DNA, directly bearing on sister chromatid cohesion. Core process. Reason: Supported by functional analysis of Rad21-SMC interfaces governing DNA-holding (cohesion). Supporting Evidence: PMID:29735656 physical and functional impairment at the interfaces of Psm1/3 hinge, Psm1 head-Rad21, or Psm3 coiled coil-Rad21. |
| GO:0000070 mitotic sister chromatid segregation | IMP PMID:11882285 Requirement of chromatid cohesion proteins rad21/scc1 and mi... | ACCEPT | Summary: Loss of cohesion in rad21-K1 perturbs microtubule-kinetochore interaction and activates the spindle checkpoint, demonstrating a requirement for Rad21 in proper mitotic sister chromatid segregation. Core process. Reason: Mutant phenotype directly links Rad21 to faithful mitotic chromosome segregation. Supporting Evidence: PMID:11882285 The loss of chromatid cohesion in fission yeast mutants (mis4-242 and rad21-K1) leads to the activation of Mad2- and Bub1-dependent checkpoint, possibly due to a diminished microtubule-kinetochore interaction. |
| GO:0005721 pericentric heterochromatin | IDA PMID:11598020 Establishment and maintenance of sister chromatid cohesion i... | ACCEPT | Summary: Cohesin is enriched at pericentromeric heterochromatin (recruited via Swi6/HP1), a hallmark localization of fission yeast cohesin and the basis for robust centromeric cohesion. Core localization. Reason: Directly observed pericentromeric localization consistent with the broad centromere-region enrichment of cohesin. Supporting Evidence: PMID:11069892 cohesin subunits are enriched in broad centromere regions |
| GO:0007064 mitotic sister chromatid cohesion | IMP PMID:10779336 Fission yeast Eso1p is required for establishing sister chro... | ACCEPT | Summary: The paper shows that establishment of cohesion during S phase requires Eso1 and uses the rad21-K1 mutant in its experiments. Consistent with Rad21's core cohesion role. Reason: Core process. The abstract's "failure to establish sister chromatid cohesion during S phase" describes the eso1 mutant, not rad21; the cached Methods show that the rad21-K1 mutant was among the strains studied, and Rad21's requirement for cohesion is well established. Supporting Evidence: PMID:10779336 The S. pombe mutant strains Ξmad2 , mis4-242 , and rad21-K1 and the strain used for visualization of Cen1-green fluorescent protein (GFP) were described previously PMID:11069892 Precocious sister chromatid separation was observed in cohesin subunit mutants, strongly suggesting that fission yeast cohesin was also required to establish sister chromatid cohesion. |
| GO:0005515 protein binding | IPI PMID:26687354 DNA Entry into and Exit out of the Cohesin Ring by an Interl... | MODIFY | Summary: This IPI captures the physical interaction of Rad21 (kleisin) with the Wapl subunit (Wpl1, SPAC10F6.09c) that governs DNA exit from the cohesin ring. Bare protein binding is uninformative; the meaningful function is Rad21's role as the kleisin bridge/adaptor that links the SMC ATPase heads and is contacted by accessory subunits. A protein-macromolecule adaptor function better describes this. Reason: Avoid uninformative protein binding. The interaction reflects Rad21's adaptor/bridging role connecting the SMC heads and accessory subunits (Wapl, Pds5, Psc3). Proposed replacements: protein-macromolecule adaptor activity Supporting Evidence: PMID:26687354 A kleisin subunit (Rad21 in fission yeast) bridges the ATPase heads and stabilizes their interaction. |
| GO:0044820 mitotic telomere tethering at nuclear periphery | IMP PMID:25778919 Aurora B prevents chromosome arm separation defects by promo... | KEEP AS NON CORE | Summary: Cohesin Rad21 (with Swi6/HP1) is involved in telomere tethering at the nuclear periphery; Aurora B promotes its dissociation to allow telomere dispersion. A genuine but specialized, non-core role. Reason: Experimentally supported but peripheral role relative to core sister chromatid cohesion. Supporting Evidence: PMID:25778919 Dispersion is promoted by the dissociation of Swi6/HP1 and cohesin Rad21 from telomeres |
| GO:0000779 condensed chromosome, centromeric region | IDA PMID:11069892 Characterization of fission yeast cohesin: essential anaphas... | ACCEPT | Summary: ChIP and immunolocalization show Rad21 enriched at the centromeric region of (mitotic) chromosomes. Core centromeric localization. Reason: Directly demonstrated centromeric-region localization. Supporting Evidence: PMID:11069892 cohesin subunits are enriched in broad centromere regions |
| GO:0000785 chromatin | IDA PMID:11069892 Characterization of fission yeast cohesin: essential anaphas... | ACCEPT | Summary: Rad21 associates with chromatin (loaded by Mis4) and is detected on chromatin by ChIP. Core localization for a cohesin subunit. Reason: Directly demonstrated chromatin association. Supporting Evidence: PMID:11069892 Mis4, another sister chromatid cohesion protein, plays an essential role for loading Rad21 on chromatin. |
| GO:0030892 mitotic cohesin complex | IDA PMID:11069892 Characterization of fission yeast cohesin: essential anaphas... | ACCEPT | Summary: Direct IDA for membership of the mitotic cohesin complex via demonstrated complex formation with Psm1/Psm3. Core component (duplicate of the IPI/IBA entries). Reason: Direct co-immunoprecipitation evidence for cohesin complex membership. Supporting Evidence: PMID:11069892 Immunoprecipitation demonstrates stable complex formation of Rad21 with Psm1 and Psm3 but not with Psc3. |
| GO:0003690 double-stranded DNA binding | IDA PMID:24291789 Biochemical reconstitution of topological DNA binding by the... | ACCEPT | Summary: Reconstituted cohesin containing Rad21 binds double-stranded DNA (ATP-independent) prior to topological loading. The contributes_to qualifier correctly attributes this complex-level DNA-binding activity to Rad21 as one subunit. Reason: Directly demonstrated dsDNA binding by the reconstituted cohesin ring containing Rad21. Supporting Evidence: PMID:24291789 The complex showed ATP-independent dsDNA binding |
| GO:0007064 mitotic sister chromatid cohesion | IDA PMID:24291789 Biochemical reconstitution of topological DNA binding by the... | ACCEPT | Summary: Biochemical reconstitution of topological DNA binding by the cohesin ring containing Rad21 provides direct evidence for the mechanism of sister chromatid cohesion. Core process. Reason: Reconstituted topological DNA entrapment is the molecular basis of sister chromatid cohesion. Supporting Evidence: PMID:24291789 Biochemical reconstitution of topological DNA binding by the cohesin ring. |
| GO:0030892 mitotic cohesin complex | IDA PMID:24291789 Biochemical reconstitution of topological DNA binding by the... | ACCEPT | Summary: Purification of the four-subunit cohesin complex including Rad21 directly confirms membership of the mitotic cohesin complex. Core component. Reason: Direct biochemical reconstitution of the complex containing Rad21. Supporting Evidence: PMID:24291789 four essential subunits Psm1, Psm3, Rad21 and Psc3 |
| GO:0006974 DNA damage response | IMP PMID:15329725 Separase-mediated cleavage of cohesin at interphase is requi... | ACCEPT | Summary: Separase-mediated cleavage of cohesin (Rad21) in interphase is required for DNA repair; rad21 mutants are defective in the UV/damage response and cohesin is hyper-modified after damage in a Rad3-dependent way. Genuine role in the DNA damage response. Reason: Mutant phenotype links Rad21/cohesin to the DNA damage response and repair. Supporting Evidence: PMID:15329725 We propose that the securin-separase complex might aid DNA repair by removing local cohesin in interphase cells. |
| GO:0007064 mitotic sister chromatid cohesion | IMP PMID:26583750 The ATPases of cohesin interface with regulators to modulate... | ACCEPT | Summary: The cohesin ATPases interface with regulators (Eco1, Wpl1) to modulate cohesin-mediated DNA tethering, the basis of sister chromatid cohesion. Core process; Rad21 is the kleisin closing this ring. Reason: Supported by functional analysis of cohesin ATPase/regulator interplay controlling DNA tethering/cohesion. Supporting Evidence: PMID:26583750 Cohesin tethers together regions of DNA, thereby mediating higher order chromatin organization that is critical for sister chromatid cohesion, DNA repair and transcriptional regulation. |
| GO:0005721 pericentric heterochromatin | IDA PMID:25847133 RNA pol II transcript abundance controls condensin accumulat... | ACCEPT | Summary: Direct localization shows Rad21/cohesin at pericentric heterochromatin (distinct from condensin sites). Core localization. Reason: Directly observed pericentromeric localization. Supporting Evidence: PMID:25847133 Mitotic enrichment of Rad21- and Top2-FLAG was commonly found at centromeres and some RNA genes, but was considerably different from that of condensin Cut14-FLAG. |
| GO:0033553 rDNA heterochromatin | IDA PMID:25847133 RNA pol II transcript abundance controls condensin accumulat... | UNDECIDED | Summary: PomBase assigns Rad21 to rDNA heterochromatin from PMID:25847133. The paper reports Rad21 enrichment at centromeres, subtelomeres, and some RNA genes, but does not explicitly identify rDNA among the Rad21 sites. Reason: Retain this experimental curator annotation without overruling it, but defer judgment because the available full text does not provide a Rad21-specific rDNA statement and the broader RNA-gene sentence is not sufficient evidence for this precise localization. |
| GO:0099115 chromosome, subtelomeric region | IDA PMID:25847133 RNA pol II transcript abundance controls condensin accumulat... | KEEP AS NON CORE | Summary: Direct localization places Rad21/cohesin at subtelomeric regions. Genuine but specialized localization; non-core relative to centromeric cohesion. Reason: Directly observed but specialized localization. Supporting Evidence: PMID:25847133 Rad21 was significantly enriched at subtelomeric regions at both ends of chromosomes 1 and 2. |
| GO:0005634 nucleus | IDA PMID:7706319 The rad21 gene product of Schizosaccharomyces pombe is a nuc... | ACCEPT | Summary: Direct evidence that Rad21 is nuclear throughout the cell cycle, with an NLS in the C-terminal third. Core localization. Reason: Direct evidence of nuclear localization. Supporting Evidence: PMID:7706319 The Rad21 protein is nuclear during the cell cycle. |
| GO:0005634 nucleus | IDA PMID:10440376 Cohesin Rec8 is required for reductional chromosome segregat... | ACCEPT | Summary: Nuclear localization of Rad21 is supported. This annotation derives from a Rec8 cohesin study; nuclear localization of Rad21 is well established. Reason: Nuclear localization is directly demonstrated by multiple studies. Whether the cited Rec8 paper also localised Rad21 cannot be verified from its abstract, which concerns Rec8 only (see source_defects); the claim is true, so the curator annotation is retained. Supporting Evidence: PMID:7706319 The Rad21 protein is nuclear during the cell cycle. |
| GO:0005634 nucleus | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: Genome-wide GFP localization study assigns Rad21 to the nucleus, consistent with all other evidence. Core localization. Reason: High-throughput localization consistent with direct evidence. Supporting Evidence: PMID:7706319 The Rad21 protein is nuclear during the cell cycle. |
| GO:0006302 double-strand break repair | IMP PMID:1480481 Cloning and characterization of rad21 an essential gene of S... | ACCEPT | Summary: Rad21 was originally identified through the radiation-sensitive, DSB-repair-deficient rad21-45 mutant; plasmid-borne rad21 fully restores the DSB repair pathway. A genuine, directly demonstrated repair function. Reason: Mutant phenotype and complementation directly demonstrate a role in double-strand break repair. Supporting Evidence: PMID:1480481 The radiation-sensitive mutant rad21-45 is deficient in this repair pathway but is capable of cell-cycle arrest in G2 following DNA damage. PMID:1480481 The plasmid-borne gene completely reestablished the DNA dsb repair pathway. |
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Download this section (compressed HTML)Q: What kinase(s) are responsible for the cell-cycle-regulated hyperphosphorylation of Rad21 during S/G2, and is this phosphorylation required for cohesion establishment versus only for anaphase proteolysis?
Q: Is the functionally essential anaphase-cleaved pool of Rad21 spatially restricted (e.g., to centromeres), explaining why only a small fraction of cleaved product is sufficient for sister separation?
Q: How are cohesin's loop-extrusion (chromatin looping) and cohesive (sister chromatid cohesion) activities partitioned at the level of the same Rad21-containing ring?
Q: Should the PomBase exists_during meiotic cell cycle extension on the GO:1990342 heterochromatin-island annotation be removed, given that PMID:22144463 assayed Rad21 enrichment in log-growing vegetative cells and Rad21 is largely replaced by Rec8 during meiosis?
Experiment: Phospho-site mutagenesis (S219, S547, S553 and N-terminal Cdc2 sites) combined with ChIP and cohesion assays to dissect the role of Rad21 phosphorylation in loading, cohesion establishment, and anaphase cleavage.
Experiment: Auxin-inducible or fast-degron depletion of Rad21 at defined cell-cycle stages followed by Hi-C/Micro-C to separate its contributions to sister chromatid cohesion versus intra-chromatid loop formation.
Experiment: Single-molecule reconstitution comparing wild-type and Psm1-Rad21 / Psm3-Rad21 interface mutants to quantify how each interface governs DNA hold versus release without separase cleavage.
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