id: P26497 gene_symbol: spo0J product_type: PROTEIN status: DRAFT taxon: id: NCBITaxon:224308 label: Bacillus subtilis subsp. subtilis str. 168 description: Spo0J is the Bacillus subtilis ParB chromosome-partitioning protein, a CTP-binding DNA clamp and CTP hydrolase. It recognizes origin-proximal parS sites and spreads onto neighboring DNA, organizing a nucleoprotein platform that recruits the Smc-ScpAB chromosome-condensation machinery for efficient segregation. CTP binding supports clamp engagement and loading; hydrolysis is dispensable for the loading steps tested in vitro and has been proposed to promote turnover or recycling. Spo0J also regulates the Soj/ParA control system for DnaA-dependent replication initiation. Through antagonism of Soj and the replication checkpoint, it contributes positively to the initiation of sporulation. existing_annotations: - term: id: GO:0005694 label: chromosome evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: is_active_in review: summary: Spo0J associates with the origin-proximal nucleoid/chromosome. action: ACCEPT reason: Direct microscopy and origin-proximal binding support the localization. The broad chromosome and nucleoid terms are consistent with the more specific bacterial-nucleoid observation. supported_by: - reference_id: PMID:9114058 supporting_text: Spo0J was associated with a region of the nucleoid proximal to the cell pole, both in growing cells dividing symmetrically and in sporulating cells dividing asymmetrically. - reference_id: file:BACSU/spo0J/spo0J-primary-scope.md supporting_text: leaf PTN002121226, below chromosome/segregation IBD PTN002121184 and positive-sporulation IBD PTN002121186. - term: id: GO:0007059 label: chromosome segregation evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in review: summary: Spo0J organizes chromosomes for faithful segregation. action: ACCEPT reason: The anucleate-cell phenotype is supplemented by direct parS DNA binding/clamp activity and recruitment of the Smc machinery. Spo0J does structural and recruitment work in segregation; this is not an annotation based solely on loss-of-function necessity. supported_by: - reference_id: PMID:8071208 supporting_text: spo0J null mutants produced a significant proportion of anucleate cells during vegetative growth. - reference_id: PMID:31649139 supporting_text: A helix-turn-helix (HTH) motif in the middle domain (M) recognizes parS DNA. - reference_id: PMID:19450517 supporting_text: insertion of parS sites near the replication terminus targets SMC to this position leading to defects in chromosome organization and segregation. - reference_id: file:BACSU/spo0J/spo0J-primary-scope.md supporting_text: leaf PTN002121226, below chromosome/segregation IBD PTN002121184 and positive-sporulation IBD PTN002121186. - term: id: GO:0045881 label: positive regulation of sporulation resulting in formation of a cellular spore evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in review: summary: Spo0J positively contributes to sporulation initiation through Soj-dependent regulation. action: ACCEPT reason: The source genetic suppression experiment establishes antagonism of Soj inhibition. A regulator can participate in sporulation without executing spore structural assembly. The later Soj-DnaA-Sda mechanism refines the route to Spo0A and does not make the broad sporulation annotation non-core or false. supported_by: - reference_id: PMID:8071208 supporting_text: These results indicate that Soj inhibits the initiation of sporulation and that Spo0J antagonizes that inhibition. - reference_id: PMID:19450516 supporting_text: 'Spo0J performs two independent functions: regulation of initiation of DNA replication via Soj and promotion of chromosome segregation by Smc recruitment.' - reference_id: file:BACSU/spo0J/spo0J-primary-scope.md supporting_text: leaf PTN002121226, below chromosome/segregation IBD PTN002121184 and positive-sporulation IBD PTN002121186. - term: id: GO:0003677 label: DNA binding evidence_type: IEA original_reference_id: GO_REF:0000120 qualifier: enables review: summary: Spo0J binds DNA, including sequence-specific parS and nonspecific flanking DNA. action: ACCEPT reason: The broad DNA-binding term accurately includes both recognition and spreading/clamp behavior. It should not be modified solely to make it more specific, and narrowing to centromeric recognition would lose the nonspecific component. supported_by: - reference_id: PMID:31649139 supporting_text: A helix-turn-helix (HTH) motif in the middle domain (M) recognizes parS DNA. - reference_id: PMID:31649139 supporting_text: Isothermal titration calorimetry (ITC) confirmed ParBBsu binding to CTP yielding dissociation constants (Kd) in the range of 10-50 μM. - term: id: GO:0007059 label: chromosome segregation evidence_type: IEA original_reference_id: GO_REF:0000043 qualifier: involved_in review: summary: Spo0J organizes chromosomes for faithful segregation. action: ACCEPT reason: The anucleate-cell phenotype is supplemented by direct parS DNA binding/clamp activity and recruitment of the Smc machinery. Spo0J does structural and recruitment work in segregation; this is not an annotation based solely on loss-of-function necessity. supported_by: - reference_id: PMID:8071208 supporting_text: spo0J null mutants produced a significant proportion of anucleate cells during vegetative growth. - reference_id: PMID:31649139 supporting_text: A helix-turn-helix (HTH) motif in the middle domain (M) recognizes parS DNA. - reference_id: PMID:19450517 supporting_text: insertion of parS sites near the replication terminus targets SMC to this position leading to defects in chromosome organization and segregation. - term: id: GO:0009295 label: nucleoid evidence_type: IEA original_reference_id: GO_REF:0000044 qualifier: located_in review: summary: Spo0J associates with the origin-proximal nucleoid/chromosome. action: ACCEPT reason: Direct microscopy and origin-proximal binding support the localization. The broad chromosome and nucleoid terms are consistent with the more specific bacterial-nucleoid observation. supported_by: - reference_id: PMID:9114058 supporting_text: Spo0J was associated with a region of the nucleoid proximal to the cell pole, both in growing cells dividing symmetrically and in sporulating cells dividing asymmetrically. - term: id: GO:0030435 label: sporulation resulting in formation of a cellular spore evidence_type: IEA original_reference_id: GO_REF:0000043 qualifier: involved_in review: summary: Spo0J positively contributes to sporulation initiation through Soj-dependent regulation. action: ACCEPT reason: The source genetic suppression experiment establishes antagonism of Soj inhibition. A regulator can participate in sporulation without executing spore structural assembly. The later Soj-DnaA-Sda mechanism refines the route to Spo0A and does not make the broad sporulation annotation non-core or false. supported_by: - reference_id: PMID:8071208 supporting_text: These results indicate that Soj inhibits the initiation of sporulation and that Spo0J antagonizes that inhibition. - reference_id: PMID:19450516 supporting_text: 'Spo0J performs two independent functions: regulation of initiation of DNA replication via Soj and promotion of chromosome segregation by Smc recruitment.' - term: id: GO:0043590 label: bacterial nucleoid evidence_type: IDA original_reference_id: PMID:9114058 qualifier: part_of review: summary: Spo0J associates with the origin-proximal nucleoid/chromosome. action: ACCEPT reason: Direct microscopy and origin-proximal binding support the localization. The broad chromosome and nucleoid terms are consistent with the more specific bacterial-nucleoid observation. supported_by: - reference_id: PMID:9114058 supporting_text: Spo0J was associated with a region of the nucleoid proximal to the cell pole, both in growing cells dividing symmetrically and in sporulating cells dividing asymmetrically. - term: id: GO:0007059 label: chromosome segregation evidence_type: IMP original_reference_id: PMID:8071208 qualifier: involved_in review: summary: Spo0J organizes chromosomes for faithful segregation. action: ACCEPT reason: The anucleate-cell phenotype is supplemented by direct parS DNA binding/clamp activity and recruitment of the Smc machinery. Spo0J does structural and recruitment work in segregation; this is not an annotation based solely on loss-of-function necessity. supported_by: - reference_id: PMID:8071208 supporting_text: spo0J null mutants produced a significant proportion of anucleate cells during vegetative growth. - reference_id: PMID:31649139 supporting_text: A helix-turn-helix (HTH) motif in the middle domain (M) recognizes parS DNA. - reference_id: PMID:19450517 supporting_text: insertion of parS sites near the replication terminus targets SMC to this position leading to defects in chromosome organization and segregation. - term: id: GO:0045881 label: positive regulation of sporulation resulting in formation of a cellular spore evidence_type: IGI original_reference_id: PMID:8071208 qualifier: involved_in review: summary: Spo0J positively contributes to sporulation initiation through Soj-dependent regulation. action: ACCEPT reason: The source genetic suppression experiment establishes antagonism of Soj inhibition. A regulator can participate in sporulation without executing spore structural assembly. The later Soj-DnaA-Sda mechanism refines the route to Spo0A and does not make the broad sporulation annotation non-core or false. supported_by: - reference_id: PMID:8071208 supporting_text: These results indicate that Soj inhibits the initiation of sporulation and that Spo0J antagonizes that inhibition. - reference_id: PMID:19450516 supporting_text: 'Spo0J performs two independent functions: regulation of initiation of DNA replication via Soj and promotion of chromosome segregation by Smc recruitment.' - term: id: GO:0043273 label: CTPase activity evidence_type: IDA original_reference_id: PMID:31649139 review: summary: Purified B. subtilis Spo0J directly hydrolyzes CTP. action: NEW reason: Retain this old authored proposal with direct target IDA evidence instead of an unsubstantiated authored IBA designation. PMID:31649139 measures phosphate production, with parS stimulation and nucleotide-site mutants. Hydrolysis is distinct from ATPase activities of partner Soj/Smc and is dispensable for the DNA-loading steps tested with CTPgammaS. supported_by: - reference_id: PMID:31649139 supporting_text: ParBBsu dimers hydrolyzed about five CTP molecules per hour. - reference_id: PMID:31649139 supporting_text: The efficient stimulation of ParB-DNA entrapment by CTPγS implies that CTP hydrolysis is dispensable for all steps of DNA loading. - term: id: GO:0002135 label: CTP binding evidence_type: IDA original_reference_id: PMID:31649139 review: summary: Spo0J directly binds CTP. action: NEW reason: Retain this distinct substrate-binding proposal with direct target ITC/radiolabel evidence. R80A disrupts binding. ATP-like motif/structural resemblance alone is not decisive; the measured target substrate is CTP. supported_by: - reference_id: PMID:31649139 supporting_text: Isothermal titration calorimetry (ITC) confirmed ParBBsu binding to CTP yielding dissociation constants (Kd) in the range of 10-50 μM. - term: id: GO:0043221 label: SMC family protein binding evidence_type: IPI original_reference_id: PMID:36044845 review: summary: Spo0J directly binds the Smc chromosome-organizing protein. action: NEW reason: Retain with direct target interface evidence. The crosslink and functional chimera study maps the ParB CTP-domain/Smc-joint interface, while parS-dependent SMC relocation demonstrates loader function. Engineered crosslinking/Smc ATPase-trap constructs identify contact geometry, not a native equilibrium affinity. supported_by: - reference_id: PMID:36044845 supporting_text: Using chimeric proteins and chemical cross-linking, we find that ParB directly binds the Smc subunit. - reference_id: PMID:19450517 supporting_text: insertion of parS sites near the replication terminus targets SMC to this position leading to defects in chromosome organization and segregation. - term: id: GO:0030174 label: regulation of DNA-templated DNA replication initiation evidence_type: IMP original_reference_id: PMID:18854156 review: summary: Spo0J regulates replication initiation through Soj. action: NEW reason: 'Retain the existing proposal: Spo0J modulates a regulatory protein that controls DnaA, and PMID:19450516 explicitly separates this target function from Smc recruitment. This is work in regulation, not an inference that any chromosome-segregation mutant must be a replication initiator. Keep the original authored PMID:18854156 and add the explicit target corroboration.' supported_by: - reference_id: PMID:19450516 supporting_text: 'Spo0J performs two independent functions: regulation of initiation of DNA replication via Soj and promotion of chromosome segregation by Smc recruitment.' references: - id: GO_REF:0000033 title: Annotation inferences using phylogenetic trees findings: [] - id: GO_REF:0000043 title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping findings: [] - id: GO_REF:0000044 title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping findings: [] - id: GO_REF:0000120 title: Combined Automated Annotation using Multiple IEA Methods findings: [] - id: PMID:8071208 title: spo0J is required for normal chromosome segregation as well as the initiation of sporulation in Bacillus subtilis. findings: - statement: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. supporting_text: These results indicate that Soj inhibits the initiation of sporulation and that Spo0J antagonizes that inhibition. reference_review: relevance: HIGH correctness: VERIFIED review_notes: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. full_text_unavailable: true - id: PMID:9114058 title: Bipolar localization of a chromosome partition protein in Bacillus subtilis. findings: - statement: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. supporting_text: Spo0J was associated with a region of the nucleoid proximal to the cell pole, both in growing cells dividing symmetrically and in sporulating cells dividing asymmetrically. reference_review: relevance: HIGH correctness: VERIFIED review_notes: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. full_text_unavailable: true - id: PMID:18854156 title: Dynamic control of the DNA replication initiation protein DnaA by Soj/ParA. findings: - statement: Spo0J regulates DNA replication initiation via Soj/ParA supporting_text: the ParA ortholog in B. subtilis (Soj) controls the activity of the DNA replication initiator protein DnaA. Subcellular localization of several Soj mutants indicates that Soj acts as a spatially regulated molecular switch, capable of either inhibiting or activating DnaA. - statement: spo0J disruption leads to increased chromosome origins supporting_text: These results suggest that the pleiotropy manifested by chromosomal parABS mutations could be the indirect effects of a primary activity regulating DNA replication initiation. - statement: Spo0J localizes to the nucleoid supporting_text: Subcellular localization of several Soj mutants indicates that Soj acts as a spatially regulated molecular switch reference_review: relevance: HIGH correctness: VERIFIED review_notes: Abstract-only primary study establishes Soj-DnaA regulation and the Sda-checkpoint explanation for sporulation effects; complemented by explicit Spo0J functional separation in PMID:19450516. full_text_unavailable: true - id: DOI:10.1093/nar/gkx271 title: A network of cis and trans interactions is required for ParB spreading. full_text_unavailable: true findings: - statement: ParB forms nucleoprotein complexes at parS and spreads to adjacent DNA - statement: Spreading requires cis/trans ParB-ParB interactions - statement: ParB can bridge DNA segments - id: DOI:10.1099/mic.0.001259 title: Regulation of DNA replication initiation by ParA is independent of parS location in Bacillus subtilis. full_text_unavailable: true findings: - statement: parS consensus sequence is 5'-TGTTCCACGTGAAACA-3' - statement: B. subtilis has multiple parS sites clustered near oriC - statement: ParA regulation of DnaA is maintained even when parS is relocated - id: DOI:10.1038/s41467-023-44509-z title: The virulence regulator VirB from Shigella flexneri uses a CTP-dependent switch mechanism to activate gene expression full_text_unavailable: true findings: - statement: ParB-family proteins are CTP-dependent DNA-sliding clamps - statement: CTP binding triggers clamp closure and DNA loading - statement: CTP-binding mutations abolish complex formation - id: DOI:10.3390/microorganisms8010105 title: Rules and Exceptions - The Role of Chromosomal ParB in DNA Segregation and Other Cellular Processes. full_text_unavailable: true findings: - statement: ParB recruits SMC-ScpAB to origin regions - statement: ParB functions in chromosome organization and segregation - id: file:BACSU/spo0J/spo0J-deep-research-falcon.md title: Deep research on spo0J (ParB) in Bacillus subtilis findings: - statement: The report supports Spo0J recruitment of chromosome-organizing machinery, corroborated by direct primary experiments. supporting_text: ParB:parS recruits SMC–ScpAB to ori region, promoting arm juxtaposition and compaction. reference_review: relevance: HIGH correctness: DISPUTED review_notes: Read full body. Correct clamp, Smc recruitment and Soj regulation synthesis. Direct target PMID:31649139 supersedes homolog-only CTP examples; its CTPgammaS loading result requires separation of binding-driven loading from the proposed hydrolysis-dependent recycling mechanism. - id: file:BACSU/spo0J/spo0J-primary-scope.md title: Spo0J reaction and phylogenetic scope check (2026-09-20) reference_review: relevance: HIGH correctness: VERIFIED review_notes: Actual PAINT ancestry and direct B. subtilis CTP/SMC evidence checked; exact source and experimentally engineered construct scope retained. - id: PMID:31649139 title: Self-organization of parS centromeres by the ParB CTP hydrolase. reference_review: relevance: HIGH correctness: VERIFIED review_notes: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. findings: - statement: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. supporting_text: ParBBsu dimers hydrolyzed about five CTP molecules per hour. - id: PMID:36044845 title: A joint-ParB interface promotes Smc DNA recruitment. reference_review: relevance: HIGH correctness: VERIFIED review_notes: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. findings: - statement: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. supporting_text: Using chimeric proteins and chemical cross-linking, we find that ParB directly binds the Smc subunit. - id: PMID:19450517 title: Recruitment of SMC by ParB-parS organizes the origin region and promotes efficient chromosome segregation. reference_review: relevance: HIGH correctness: VERIFIED review_notes: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. findings: - statement: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. supporting_text: insertion of parS sites near the replication terminus targets SMC to this position leading to defects in chromosome organization and segregation. - id: PMID:19450516 title: Recruitment of condensin to replication origin regions by ParB/SpoOJ promotes chromosome segregation in B. subtilis. reference_review: relevance: HIGH correctness: VERIFIED review_notes: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. full_text_unavailable: true findings: - statement: Direct primary target evidence with methods/access caveats detailed in spo0J-primary-scope.md. supporting_text: 'Spo0J performs two independent functions: regulation of initiation of DNA replication via Soj and promotion of chromosome segregation by Smc recruitment.' core_functions: - description: Sequence-specific recognition of parS and CTP-dependent clamp engagement/spreading build an origin-associated partition platform. The protein also associates with nonspecific flanking DNA. molecular_function: id: GO:0043565 label: sequence-specific DNA binding directly_involved_in: - id: GO:0007059 label: chromosome segregation locations: - id: GO:0043590 label: bacterial nucleoid supported_by: - reference_id: PMID:31649139 supporting_text: A helix-turn-helix (HTH) motif in the middle domain (M) recognizes parS DNA. - reference_id: PMID:31649139 supporting_text: Isothermal titration calorimetry (ITC) confirmed ParBBsu binding to CTP yielding dissociation constants (Kd) in the range of 10-50 μM. - reference_id: PMID:9114058 supporting_text: Spo0J was associated with a region of the nucleoid proximal to the cell pole, both in growing cells dividing symmetrically and in sporulating cells dividing asymmetrically. - description: CTP hydrolysis is directly measured and stimulated by parS. Loading with CTPgammaS shows that hydrolysis is not required for initial clamp loading; unloading/recycling is a proposed consequence in the 2019 study. molecular_function: id: GO:0043273 label: CTPase activity directly_involved_in: - id: GO:0007059 label: chromosome segregation supported_by: - reference_id: PMID:31649139 supporting_text: ParBBsu dimers hydrolyzed about five CTP molecules per hour. - reference_id: PMID:31649139 supporting_text: The efficient stimulation of ParB-DNA entrapment by CTPγS implies that CTP hydrolysis is dispensable for all steps of DNA loading. - description: Spo0J binds Smc and recruits the Smc-ScpAB chromosome-organizing machinery to parS-associated DNA, contributing directly to chromosome segregation. molecular_function: id: GO:0043221 label: SMC family protein binding directly_involved_in: - id: GO:0007059 label: chromosome segregation locations: - id: GO:0043590 label: bacterial nucleoid supported_by: - reference_id: PMID:36044845 supporting_text: Using chimeric proteins and chemical cross-linking, we find that ParB directly binds the Smc subunit. - reference_id: PMID:19450517 supporting_text: insertion of parS sites near the replication terminus targets SMC to this position leading to defects in chromosome organization and segregation. - reference_id: file:BACSU/spo0J/spo0J-deep-research-falcon.md supporting_text: ParB:parS recruits SMC–ScpAB to ori region, promoting arm juxtaposition and compaction. - description: The DNA-associated Spo0J regulator controls Soj-dependent replication-initiation regulation and antagonizes Soj inhibition of sporulation. Its CTPase chemistry should not be confused with the ATPase activity of Soj or Smc. molecular_function: id: GO:0003677 label: DNA binding directly_involved_in: - id: GO:0030174 label: regulation of DNA-templated DNA replication initiation - id: GO:0045881 label: positive regulation of sporulation resulting in formation of a cellular spore supported_by: - reference_id: PMID:19450516 supporting_text: 'Spo0J performs two independent functions: regulation of initiation of DNA replication via Soj and promotion of chromosome segregation by Smc recruitment.' - reference_id: PMID:8071208 supporting_text: These results indicate that Soj inhibits the initiation of sporulation and that Spo0J antagonizes that inhibition. proposed_new_terms: [] suggested_questions: - question: Which turnover/unloading steps in native Spo0J partition complexes require CTP hydrolysis, as distinct from CTP-binding-driven loading? - question: Which GO term best captures Spo0J-mediated SMC recruitment to bacterial parS regions, given the mitotic-spindle wording in the centromeric-region terminology? - question: What is the detailed coupling between Spo0J clamp state, Soj regulation and the DnaA/Sda sporulation checkpoint? suggested_experiments: - description: Biochemical characterization of B. subtilis Spo0J CTPase activity and kinetic parameters hypothesis: Spo0J hydrolyzes CTP with kinetics similar to other characterized ParB homologs experiment_type: enzyme kinetics assay - description: ChIP-seq to map Spo0J spreading patterns from parS sites at different cell cycle stages hypothesis: Spo0J spreading extent varies with cell cycle stage and CTP availability experiment_type: ChIP-seq - description: Structural analysis of Spo0J-SMC interaction interface hypothesis: Specific residues in the Spo0J C-terminal domain mediate SMC recruitment experiment_type: structural biology