identifier: traitmech:000213 label: phosphorothioate defense system definition: A genomics trait describing possession of a DNA phosphorothioation-dependent antiviral locus in which host DNA phosphorothioate modification is paired with a Dnd-, Ssp-, or Pbe-family effector module to restrict invading viral DNA. definition_source: DOI:10.1038/s41564-020-0700-6 trait_category: GENOMICS term_kind: CLASS mapping_status: PROPOSED parent_traits: - traitmech:000209 synonyms: - synonym_text: PT-associated R-M system synonym_type: EXACT_SYNONYM source: DOI:10.1128/mbio.00933-23 - synonym_text: PT-related R-M system synonym_type: EXACT_SYNONYM source: DOI:10.1128/mbio.00933-23 evidence: - reference: DOI:10.1038/s41564-020-0700-6 snippet: We previously identified the Dnd system, which uses DndABCDE to insert sulfur into the DNA backbone as a double-stranded phosphorothioate (PT) modification, and DndFGH, a restriction component notes: Xiong et al. summarize the Dnd modification and restriction modules as a DNA phosphorothioation defense system. - reference: DOI:10.1038/s41564-020-0700-6 snippet: SspABCD coupled with SspE provides protection against phages notes: Xiong et al. support SspABCD-SspE as a bacterial phosphorothioation-sensing antiphage defense system. - reference: DOI:10.1128/mbio.00933-23 snippet: Usually, this modification gene cluster is paired with a restriction module consisting of DndF, DndG, and DndH notes: Jiang et al. support the paired modification-plus-restriction architecture of Dnd-related phosphorothioate R-M systems. - reference: DOI:10.1128/mbio.00933-23 snippet: the host could benefit from the protection provided by Dnd-related R-M systems against infection by various lytic phages as well as temperate phages notes: Jiang et al. experimentally demonstrated broad antiphage protection by Dnd-related phosphorothioate R-M systems. - reference: DOI:10.1038/s41467-019-09390-9 snippet: DndCDEA-specific DNA phosphorothioate (PT) modification and the PbeABCD-mediated halt of virus propagation notes: Xiong et al. support DndCDEA-PbeABCD as an archaeal phosphorothioation-dependent antiviral branch distinct from bacterial DndFGH and Ssp systems. canonical_examples: - taxon_id: NCBITaxon:340184 taxon_label: Escherichia coli B7A note: Jiang et al. cloned the native E. coli B7A dndBCDE-FGH module into E. coli DH10B and measured strong DndB7A R-M protection against multiple lytic phages. reference: DOI:10.1128/mbio.00933-23 causal_graphs: - graph_id: phosphorothioate_dna_restriction_antiviral_defense title: Phosphorothioate restriction modules target invading viral DNA description: Evidence-backed process sketch linking host DNA phosphorothioate modification to PT-dependent self/non-self discrimination, restriction of invading viral DNA, and impaired viral DNA replication. scope_status: NONMECHANISTIC scope_notes: The graph captures system-level logic shared by phosphorothioate-based Dnd, Ssp, and Pbe antiviral systems without claiming that DndFGH, SspE, SspFGH, and PbeABCD sense PT marks, damage foreign DNA, or inhibit viral replication by one exact protein mechanism. nodes: - node_id: phosphorothioate_modification_module label: phosphorothioate modification module node_type: GENETIC_ELEMENT description: A Dnd-, Ssp-, or Pbe-paired gene module that installs sequence-specific phosphorothioate modifications on host DNA. - node_id: dna_phosphorothioation label: DNA phosphorothioation node_type: BIOLOGICAL_PROCESS description: Replacement of a nonbridging oxygen in the DNA phosphate backbone with sulfur. - node_id: pt_dependent_foreign_dna_targeting label: PT-dependent foreign DNA targeting node_type: BIOLOGICAL_PROCESS description: Phosphorothioate-dependent self/non-self discrimination that targets invading DNA for restriction. - node_id: viral_dna_restriction label: viral DNA restriction node_type: BIOLOGICAL_PROCESS description: Restriction of invading viral DNA by a PT-associated Dnd, Ssp, or Pbe effector module. - node_id: viral_dna_replication label: viral DNA replication node_type: BIOLOGICAL_PROCESS description: Replication of invading viral DNA after host cell entry. - node_id: phosphorothioate_defense_system_trait label: phosphorothioate defense system node_type: TRAIT grounding: traitmech:000213 description: Possession of a genome-encoded phosphorothioate-based antiviral defense system. - node_id: phage_defense_system label: phage defense system node_type: TRAIT grounding: traitmech:000209 description: Possession of one or more genome-encoded immune systems that inhibit viral infection. edges: - subject: phosphorothioate_modification_module predicate: contributes to predicate_id: RO:0002326 object: dna_phosphorothioation description: DndABCDE or SspABCD modification modules install sequence-specific phosphorothioate marks on host DNA. evidence: - reference: DOI:10.1038/s41564-020-0700-6 snippet: uses DndABCDE to insert sulfur into the DNA backbone as a double-stranded phosphorothioate (PT) modification notes: Xiong et al. support DndABCDE-dependent host DNA phosphorothioation. - reference: DOI:10.1038/s41564-020-0700-6 snippet: SspABCD confers single-stranded and high-frequency PTs with SspB acting as a nickase notes: Xiong et al. support SspABCD-dependent host DNA phosphorothioation. - subject: dna_phosphorothioation predicate: contributes to predicate_id: RO:0002326 object: pt_dependent_foreign_dna_targeting description: Sequence-specific PT marks couple host DNA modification to PT-dependent self/non-self restriction by Dnd-, Ssp-, and Pbe-family effector modules. evidence: - reference: DOI:10.1038/s41564-020-0700-6 snippet: SspE senses sequence-specific PTs by virtue of its PT-stimulated NTPase activity to exert its anti-phage activity notes: Xiong et al. support direct coupling between sequence-specific PT marks and SspE restriction activity. - subject: pt_dependent_foreign_dna_targeting predicate: activates predicate_id: RO:0002213 object: viral_dna_restriction description: Dnd, Ssp, and Pbe phosphorothioation-dependent systems converge on restriction of viral DNA lacking host PT marks. evidence: - reference: DOI:10.1038/s41564-020-0700-6 snippet: SspE inhibits phage propagation by introducing nicking damage to impair phage DNA replication notes: Xiong et al. support SspE-linked nicking damage as a second PT-dependent route to restricted phage replication. - reference: DOI:10.1128/mbio.00933-23 snippet: DndF, DndG, and DndH undergoes conformational changes to perform DNA binding, translocation, and DNA nicking activities and scavenge the foreign DNA notes: Jiang et al. summarize DndFGH-mediated DNA binding, translocation, and nicking of foreign DNA that lacks PT modification. - reference: DOI:10.1038/s41467-019-09390-9 snippet: PbeABCD exerted antiviral activity depending on the presence of PT modifications notes: Xiong et al. support PT-dependent PbeABCD antiviral activity. - subject: viral_dna_restriction predicate: mitigates predicate_id: METPO:2007407 object: viral_dna_replication description: PT-dependent effector activity inhibits replication of invading viral DNA. evidence: - reference: DOI:10.1038/s41564-020-0700-6 snippet: SspE inhibits phage propagation by introducing nicking damage to impair phage DNA replication notes: Xiong et al. directly connect SspE DNA nicking to impaired phage replication. - reference: DOI:10.1038/s41467-019-09390-9 snippet: PbeABCD-mediated halt of virus propagation via inhibition of DNA replication notes: Xiong et al. connect PbeABCD-dependent PT restriction to inhibited archaeal viral DNA replication. - subject: viral_dna_restriction predicate: confers predicate_id: METPO:2007700 object: phosphorothioate_defense_system_trait description: Restriction of invading viral DNA realizes phosphorothioate-based antiviral defense. evidence: - reference: DOI:10.1128/mbio.00933-23 snippet: the host could benefit from Dnd-related R-M systems for a broad range of antiphage activities notes: Jiang et al. support Dnd-mediated phosphorothioate restriction as an antiphage defense output. - reference: DOI:10.1038/s41467-019-09390-9 snippet: a new type of PT-based virus resistance system notes: Xiong et al. place DndCDEA-PbeABCD in the PT antiviral defense family. - subject: phosphorothioate_defense_system_trait predicate: is a predicate_id: rdfs:subClassOf object: phage_defense_system description: Phosphorothioate restriction-system possession is an antiviral defense-system trait. evidence: - reference: DOI:10.1038/s41564-020-0700-6 snippet: provides protection against phages notes: Xiong et al. place PT-dependent SspABCD-SspE in the antiphage defense family. - reference: DOI:10.1038/s41467-019-09390-9 snippet: a new type of PT-based virus resistance system notes: Xiong et al. place DndCDEA-PbeABCD in the PT antiviral defense family. discussions: - discussion_id: phosphorothioate-subfamily-split-gap prompt: Resolve archaeal phosphorothioate-based antiviral systems before minting additional narrower children under the phosphorothioate defense parent. kind: KNOWLEDGE_GAP status: RESOLVED rationale: Dnd, SspABCD-SspE, SspABCD-SspFGH, and archaeal DndCDEA-PbeABCD PT antiviral architectures have all been split out as narrower phosphorothioate defense system children. posed_by: codex posed_date: '2026-09-15' curation_history: - timestamp: '2026-09-15T10:54:22Z' curator: codex action: MINTED_TRAITMECH_ID changes: Minted phosphorothioate defense system as a DOI-backed GENOMICS TraitRecord under the phage defense system parent after an ignored-and-hidden duplicate review found no exact live TraitMech, METPO, or prior proposal record; the replacement placeholder is reserved in proposals/metpo_traitmech_v90. llm_assisted: true - timestamp: '2026-09-15T16:03:59Z' curator: codex action: RESOLVE_DISCUSSION_SCOPE changes: Removed Dnd from the open phosphorothioate subfamily split-gap discussion after minting traitmech:000221 for the Dnd system; SspE, SspFGH, and archaeal phosphorothioate-based antiviral systems remain open. llm_assisted: true - timestamp: '2026-09-15T16:38:07Z' curator: codex action: RESOLVE_DISCUSSION_SCOPE changes: Removed SspBCD-E from the open phosphorothioate subfamily split-gap discussion after minting traitmech:000222 for the SspABCD-SspE system; SspFGH and archaeal phosphorothioate-based antiviral systems remain open. llm_assisted: true - timestamp: '2026-09-15T17:06:07Z' curator: codex action: RESOLVE_DISCUSSION_SCOPE changes: Removed SspFGH from the open phosphorothioate subfamily split-gap discussion after minting traitmech:000223 for the SspABCD-SspFGH system; archaeal phosphorothioate-based antiviral systems remain open. llm_assisted: true - timestamp: '2026-09-15T17:36:17Z' curator: codex action: RESOLVE_DISCUSSION_SCOPE changes: Minted traitmech:000224 for the archaeal DndCDEA-PbeABCD system, broadened the phosphorothioate defense system parent from bacteriophage-only Dnd/Ssp wording to Dnd/Ssp/Pbe viral-DNA restriction wording, and marked the phosphorothioate subfamily split-gap discussion resolved. llm_assisted: true