identifier: traitmech:000334 label: ApeA system definition: A phage defense system in which an organism possesses a single-component ApeA locus represented by the DefenseFinder Gao_Ape__ApeA profile, encoding an oligomeric HEPN-domain antiviral ribonuclease whose activation can cleave RNA substrates to restrict bacteriophage infection. definition_source: DOI:10.64898/2026.01.26.701840 trait_category: GENOMICS term_kind: CLASS mapping_status: PROPOSED parent_traits: - traitmech:000209 synonyms: - synonym_text: ApeA synonym_type: RELATED_SYNONYM source: DOI:10.64898/2026.01.26.701840 - synonym_text: Gao_Ape synonym_type: RELATED_SYNONYM source: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md evidence: - reference: DOI:10.64898/2026.01.26.701840 snippet: Here, we focus on ApeA, a HEPN-domain antiviral protein that confers immunity through cleavage of host tRNAs within their anticodon loops. notes: Juozapaitis et al. describe ApeA as a HEPN-domain antiviral protein that cleaves host tRNAs within their anticodon loops. - reference: DOI:10.64898/2026.01.26.701840 snippet: Both ApeA homologs confer protection at low MOI but not at high MOI, when most cells are infected notes: Juozapaitis et al. show that Ec1ApeA and Ec2ApeA protect at low multiplicity of infection but not high multiplicity, supporting abortive-infection behavior. - reference: DOI:10.64898/2026.01.26.701840 snippet: activity of Ec1ApeA and Ec2ApeA proteins was abrogated by HEPN active site R521A and R502A mutations respectively notes: HEPN active-site mutations abrogated antiviral activity in the tested Ec1ApeA and Ec2ApeA proteins. - reference: DOI:10.64898/2026.01.26.701840 snippet: Together, these results demonstrate that Ec1ApeA exhibits endoribonuclease activity targeting the tRNA anticodon loop, which is specifically activated during bacteriophage infection. notes: Ec1ApeA exhibits infection-activated endoribonuclease activity targeting the tRNA anticodon loop. - reference: DOI:10.64898/2026.01.26.701840 snippet: In vitro ribonuclease assays showed that under our experimental conditions tRNA cleavage by wild-type Ec2ApeA was activated by dpCG notes: Ec2ApeA tRNA cleavage can be activated by deoxydinucleotides in vitro, supporting ligand-stimulated ApeA RNase activity for one ApeA variant. - reference: DOI:10.64898/2026.03.20.713152 snippet: We show that two ApeA homologs, Ec1ApeA and Ps2ApeA, protect against a variety of single-stranded RNA phages. notes: Drobysheva et al. show that Ec1ApeA and Ps2ApeA protect against single-stranded RNA phages. - reference: DOI:10.64898/2026.03.20.713152 snippet: results show that ApeA stops RNA phage replication by directly cleaving the phage genome. notes: Drobysheva et al. support direct phage-genome cleavage as an ApeA RNA-phage defense output. - reference: DOI:10.64898/2026.03.20.713152 snippet: In the case of infection with RNA phages, we did not see evidence for induced cell death by Ec1ApeA notes: Drobysheva et al. distinguish Ec1ApeA RNA-phage defense from cell-death abortive infection. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: Gao_Ape | 10\.1126/science\.aba0372 | Diverse enzymatic activities mediate antiviral immunity in prokaryotes notes: The DefenseFinder article registry maps the named Gao_Ape system to the Gao et al. prokaryotic antiviral-immunity paper. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv snippet: "Gao_Ape\tGao_Ape\t1\t1\tGao_Ape__ApeA\t\t\t" notes: The DefenseFinder rules table models Gao_Ape as a single-mandatory-profile system with the Gao_Ape__ApeA profile. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md snippet: '| Gao_Ape__ApeA | Gao_Ape__ApeA | Gao_Ape | Custom | 18 |' notes: The DefenseFinder HMM inventory records ApeA under the Gao_Ape model namespace. causal_graphs: - graph_id: gao_ape_hepn_rnase_restricts_phage title: ApeA loci activate HEPN RNase antiphage outputs description: Conservative system-level sketch linking a Gao_Ape/ApeA locus to HEPN RNase activation, host tRNA anticodon-loop cleavage during DNA-phage abortive infection, phage genomic RNA cleavage during non-abortive RNA-phage defense, and the ApeA system trait. scope_status: NONMECHANISTIC scope_notes: The graph captures ApeA as a named DefenseFinder single-component system with alternate HEPN RNase outputs while leaving natural-host accession breadth, homolog- and phage-class-specific trigger differences, direct RNA-loop sensing by Ec1ApeA, the exact DNA-phage nuclease inputs to Ec2ApeA deoxydinucleotide signaling, and activity of additional homologs unresolved. nodes: - node_id: gao_ape_locus label: Gao_Ape locus node_type: GENETIC_ELEMENT description: A single-component ApeA antiphage locus represented by the DefenseFinder Gao_Ape__ApeA profile. - node_id: apea_hepn_rnase_activity label: ApeA HEPN RNase activity node_type: MOLECULAR_FUNCTION description: Triggered ApeA ribonuclease activity dependent on HEPN active-site residues. - node_id: trna_anticodon_loop_cleavage label: tRNA anticodon-loop cleavage node_type: BIOLOGICAL_PROCESS description: Cleavage of host tRNAs within their anticodon loops by activated ApeA HEPN RNase. - node_id: abortive_phage_restriction label: abortive phage restriction node_type: BIOLOGICAL_PROCESS description: Abortive-infection defense in which ApeA-mediated translation arrest restricts bacteriophage propagation. - node_id: phage_genomic_rna_cleavage label: phage genomic RNA cleavage node_type: BIOLOGICAL_PROCESS description: Direct ApeA-dependent cleavage of an RNA-phage genome by activated HEPN RNase. - node_id: non_abortive_rna_phage_restriction label: non-abortive RNA-phage restriction node_type: BIOLOGICAL_PROCESS description: Restriction of single-stranded RNA-phage replication without inducing ApeA-dependent host-cell death. - node_id: apea_system_trait label: ApeA system node_type: TRAIT grounding: traitmech:000334 description: Possession of a genome-encoded ApeA phage-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 bacteriophage infection. edges: - subject: gao_ape_locus predicate: contributes to predicate_id: RO:0002326 object: apea_hepn_rnase_activity description: ApeA loci encode a HEPN-domain antiviral RNase, and DefenseFinder models Gao_Ape as a single-profile ApeA system. evidence: - reference: DOI:10.64898/2026.01.26.701840 snippet: Here, we focus on ApeA, a HEPN-domain antiviral protein that confers immunity through cleavage of host tRNAs within their anticodon loops. notes: Juozapaitis et al. connect ApeA to HEPN-domain antiviral RNase activity. - reference: DOI:10.64898/2026.01.26.701840 snippet: activity of Ec1ApeA and Ec2ApeA proteins was abrogated by HEPN active site R521A and R502A mutations respectively notes: HEPN active-site mutations eliminated activity in Ec1ApeA and Ec2ApeA. - reference: DOI:10.64898/2026.03.20.713152 snippet: We show that two ApeA homologs, Ec1ApeA and Ps2ApeA, protect against a variety of single-stranded RNA phages. notes: Drobysheva et al. support HEPN-dependent Ec1ApeA and Ps2ApeA RNA-phage defense. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv snippet: "Gao_Ape\tGao_Ape\t1\t1\tGao_Ape__ApeA\t\t\t" notes: The DefenseFinder rules table models Gao_Ape as a single-mandatory-profile system with the Gao_Ape__ApeA profile. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md snippet: '| Gao_Ape__ApeA | Gao_Ape__ApeA | Gao_Ape | Custom | 18 |' notes: The DefenseFinder HMM inventory records ApeA under the Gao_Ape model namespace. - subject: apea_hepn_rnase_activity predicate: contributes to predicate_id: RO:0002326 object: trna_anticodon_loop_cleavage description: Activated ApeA HEPN RNase cleaves host tRNAs within their anticodon loops. evidence: - reference: DOI:10.64898/2026.01.26.701840 snippet: Together, these results demonstrate that Ec1ApeA exhibits endoribonuclease activity targeting the tRNA anticodon loop, which is specifically activated during bacteriophage infection. notes: Ec1ApeA endoribonuclease activity targets the tRNA anticodon loop during phage infection. - reference: DOI:10.64898/2026.01.26.701840 snippet: In vitro ribonuclease assays showed that under our experimental conditions tRNA cleavage by wild-type Ec2ApeA was activated by dpCG notes: Ec2ApeA tRNA-cleavage activity can be reconstituted in vitro with deoxydinucleotide ligands. - subject: trna_anticodon_loop_cleavage predicate: contributes to predicate_id: RO:0002326 object: abortive_phage_restriction description: ApeA-mediated host tRNA cleavage arrests translation during abortive phage defense. evidence: - reference: DOI:10.64898/2026.01.26.701840 snippet: We further demonstrate that ApeA functions as an abortive infection system by cleaving host tRNAs within their anticodon loops to arrest translation notes: Juozapaitis et al. link ApeA tRNA anticodon-loop cleavage to translation arrest during abortive infection. - subject: abortive_phage_restriction predicate: confers predicate_id: METPO:2007700 object: apea_system_trait description: ApeA low-MOI protection and abortive infection realize the ApeA system possession trait. evidence: - reference: DOI:10.64898/2026.01.26.701840 snippet: Both ApeA homologs confer protection at low MOI but not at high MOI, when most cells are infected notes: Ec1ApeA and Ec2ApeA low-MOI protection supports ApeA as an abortive infection system. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: Gao_Ape | 10\.1126/science\.aba0372 | Diverse enzymatic activities mediate antiviral immunity in prokaryotes notes: The DefenseFinder article registry maps the named Gao_Ape system to the Gao et al. prokaryotic antiviral-immunity paper. - subject: apea_hepn_rnase_activity predicate: contributes to predicate_id: RO:0002326 object: phage_genomic_rna_cleavage description: Ec1ApeA HEPN RNase activity cleaves infecting RNA-phage genomes. evidence: - reference: DOI:10.64898/2026.03.20.713152 snippet: results show that ApeA stops RNA phage replication by directly cleaving the phage genome. notes: Drobysheva et al. show that ApeA can stop RNA-phage replication by direct phage-genome cleavage. - subject: phage_genomic_rna_cleavage predicate: contributes to predicate_id: RO:0002326 object: non_abortive_rna_phage_restriction description: ApeA-dependent cleavage of the phage genome restricts RNA-phage replication without host-cell death. evidence: - reference: DOI:10.64898/2026.03.20.713152 snippet: results show that ApeA stops RNA phage replication by directly cleaving the phage genome. notes: Direct phage-genome cleavage is the main ApeA output in the assayed RNA-phage infection model. - reference: DOI:10.64898/2026.03.20.713152 snippet: In the case of infection with RNA phages, we did not see evidence for induced cell death by Ec1ApeA notes: Drobysheva et al. found no evidence for Ec1ApeA-induced cell death during RNA-phage infection. - subject: non_abortive_rna_phage_restriction predicate: confers predicate_id: METPO:2007700 object: apea_system_trait description: Non-abortive RNA-phage restriction realizes one ApeA system defense output. evidence: - reference: DOI:10.64898/2026.03.20.713152 snippet: We show that two ApeA homologs, Ec1ApeA and Ps2ApeA, protect against a variety of single-stranded RNA phages. notes: Drobysheva et al. show that ApeA homologs can protect against single-stranded RNA phages. - subject: apea_system_trait predicate: is a predicate_id: rdfs:subClassOf object: phage_defense_system description: ApeA system possession is a phage-defense-system trait. evidence: - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: Gao_Ape | 10\.1126/science\.aba0372 | Diverse enzymatic activities mediate antiviral immunity in prokaryotes notes: The DefenseFinder article registry maps the named Gao_Ape system to the Gao et al. prokaryotic antiviral-immunity paper. discussions: - discussion_id: apea-trigger-and-homolog-scope-gap prompt: Resolve ApeA natural-host loci, homolog-specific DNA-phage versus RNA-phage triggers, phage nuclease inputs, phage genomic RNA targets, abortive versus non-abortive outputs, and subtype activity before minting narrower ApeA mechanism children. kind: KNOWLEDGE_GAP status: OPEN rationale: Juozapaitis et al. support DNA-phage ApeA abortive infection through host tRNA anticodon-loop cleavage, Drobysheva et al. support non-abortive RNA-phage defense through phage-genomic-RNA cleavage, and DefenseFinder models Gao_Ape with the Gao_Ape__ApeA profile. This first record stays at system level because the curated evidence leaves homolog- and phage-class-specific trigger logic, the full DNA-versus-RNA substrate split, activity of additional homologs, and accession-level natural-host breadth unresolved. attaches_to: - causal_graphs#gao_ape_hepn_rnase_restricts_phage posed_by: codex posed_date: '2026-09-21' curation_history: - timestamp: '2026-09-21T11:03:58Z' curator: codex action: MINTED_TRAITMECH_ID changes: Minted ApeA system as a DOI-backed GENOMICS TraitRecord under phage defense system after an ignored-and-hidden duplicate review found no exact live TraitMech, METPO, history, or prior proposal record; the replacement placeholder is reserved in proposals/metpo_traitmech_v211. llm_assisted: true - timestamp: '2026-09-21T11:04:58Z' curator: codex action: REVIEW_CANONICAL_EXAMPLE_EVIDENCE_GAP changes: 'Reviewed the ApeA canonical_examples gap and left canonical_examples empty: the current evidence supports a named single-component phage-defense system, DefenseFinder Gao_Ape/ApeA profiles, and heterologously assayed ApeA homologs, but does not yet cite a directly observed natural microbial taxon with a source-backed Gao_Ape/ApeA locus. No paid research was used.' llm_assisted: true - timestamp: '2026-09-21T11:20:58Z' curator: codex action: ADDRESS_PR_REVIEW changes: Broadened the ApeA root definition, graph, evidence, and discussion after the PR 1190 adversarial review filed issue 1191, adding the March 2026 RNA-phage ApeA preprint and separating Juozapaitis host-tRNA abortive infection from Drobysheva phage-genomic-RNA non-abortive restriction. llm_assisted: true