TraitMech

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Hna system

traitmech:000241 · CLASS · PROPOSED

A phage defense system in which an organism possesses an Hna locus encoding a single SF2 helicase/nuclease effector that protects cells from bacteriophage infection by responding to phage single-stranded DNA-binding protein challenge, shifting toward dysregulated nuclease activation, and triggering abortive infection.

Trait evidence (6)

  • DOI:10.1016/j.chom.2023.01.010
    single phage defense protein, Hna, that provides protection against diverse phages in Sinorhizobium meliloti

    Sather et al. support Hna as a single-protein phage-defense determinant in S. meliloti.

  • DOI:10.1016/j.chom.2023.01.010
    Homologs of Hna are distributed widely across bacterial lineages

    Sather et al. support placing Hna at a bacterial family level rather than curating only the S. meliloti instance.

  • DOI:10.1016/j.chom.2023.01.010
    Hna contains superfamily II helicase motifs at its N terminus and a nuclease motif at its C terminus, with mutagenesis of these motifs inactivating viral defense

    Sather et al. connect the predicted helicase/nuclease domain architecture to Hna antiphage activity.

  • DOI:10.1038/s41467-026-73157-2
    Hna is a broadly distributed anti-phage immune system that confers resistance against diverse phage by eliciting an abortive infection response

    Hooper et al. independently support Hna as a named anti-phage immune system with abortive-infection output.

  • DOI:10.1038/s41467-026-73157-2
    shifts catalytic partitioning toward dysregulated nuclease activation

    Hooper et al. support phage single-stranded DNA-binding protein as a direct stimulus for Hna nuclease activation.

  • DOI:10.1016/j.chom.2023.01.010
    Hna limits phage spread by initiating abortive infection in response to a phage protein

    Sather et al. support abortive infection in response to a phage-encoded protein as the Hna phage-defense output.

Hna nuclease activation couples phage SSB challenge to abortive infection

Evidence-backed process sketch linking an Hna locus to phage single-stranded DNA-binding protein challenge, dysregulated helicase/nuclease activity, abortive infection, and inhibition of phage spread.

NONMECHANISTIC · The graph captures Sather et al. and Hooper et al. Hna phage-SSB-triggered abortive infection evidence without asserting one universal phage trigger, escape route, DNA substrate, ATP-concentration gate, or host-cell-death timing across all Hna homologs.

Hna nuclease activation couples phage SSB challenge to abortive infection Interactive directed graph showing evidence-backed causal relationships for Hna system.

Edge evidence

  • Hna locus contributes to Hna nuclease activation RO:0002326

    Hna loci encode SF2 helicase/nuclease proteins whose conserved helicase and nuclease motifs are required for viral defense.

    • DOI:10.1016/j.chom.2023.01.010 mutagenesis of these motifs inactivating viral defense Sather et al. connect Hna helicase and nuclease motifs to antiphage activity.
  • phage SSB stimulation activates Hna nuclease activation RO:0002213

    A phage-encoded single-stranded DNA-binding protein stimulates Hna and shifts it toward dysregulated nuclease activation.

    • DOI:10.1016/j.chom.2023.01.010 A similar host cell response is triggered in cells containing Hna upon expression of a phage-encoded single-stranded DNA binding protein (SSB) Sather et al. support Hna response to a phage SSB independently of whole-phage infection.
    • DOI:10.1038/s41467-026-73157-2 shifts catalytic partitioning toward dysregulated nuclease activation Hooper et al. directly connect phage SSB stimulation to Hna nuclease activation.
  • Hna nuclease activation contributes to abortive infection response RO:0002326

    Dysregulated Hna nuclease activation damages DNA, causes cellular toxicity, and contributes to the abortive infection response.

    • DOI:10.1038/s41467-026-73157-2 Disruption of this balance enhances DNA cleavage and causes cellular toxicity Hooper et al. support Hna nuclease dysregulation as a toxic DNA-cleavage output.
    • DOI:10.1016/j.chom.2023.01.010 infected cells carrying the system die but do not release phage progeny Sather et al. support the abortive infection host-cell fate of Hna-containing cells.
  • abortive infection response confers Hna system METPO:2007700

    Hna-mediated abortive infection is the phage-defense output that realizes the Hna system trait.

    • DOI:10.1016/j.chom.2023.01.010 Hna limits phage spread by initiating abortive infection in response to a phage protein Sather et al. support abortive infection as the Hna antiviral output.
  • Hna system is a phage defense system rdfs:subClassOf

    Hna system possession is a phage-defense-system trait.

    • DOI:10.1038/s41467-026-73157-2 Hna is a broadly distributed anti-phage immune system Hooper et al. place Hna in the anti-phage immune-system family.

Provenance

Identifier source
TraitMech local identifier
Definition source
DOI:10.1016/j.chom.2023.01.010

Parent traits (1)

Synonyms (1)

  • Hna anti-phage defense system EXACT_SYNONYM · DOI:10.1038/s41467-026-73157-2

kg-microbe context

No kg-microbe node embedding matched this record in the 2026-04-25 deepwalk.

Canonical examples (1)

Organisms cited as exemplars of this trait. Taxon ids are NCBITaxon and link out to the NCBI record.

  • Sinorhizobium meliloti NCBITaxon:382 DOI:10.1016/j.chom.2023.01.010 Sather et al. showed that Sinorhizobium meliloti Hna provides protection against diverse bacteriophages and triggers abortive infection in phage-infected cells.

Discussions and Knowledge Gaps (1)

Open questions attached to this trait. Seeded by just knowledge-gap-scan and curated; see the corpus-wide index.

Resolve Hna trigger breadth, phage escape routes, and family architecture before minting narrower Hna mechanism children.

KNOWLEDGE GAP OPEN hna-trigger-and-family-breadth-gap · raised by codex · 2026-09-18

Not yet attached to a section of this record — a curator sets attaches_to (e.g. causal_graphs#some_edge) so the gap shows beside the mechanism it concerns.

Sather et al. support Sinorhizobium Hna abortive infection after phage infection or phage SSB expression, and Hooper et al. support 5A SSB stimulation of nuclease activation, but Hna homologs need separate review before TraitMech asserts one universal phage trigger, ATP-dependent activation gate, DNA substrate, escape route, or host death timing across the full Hna family.

Curation history

  1. · MINTED_TRAITMECH_ID · codex

    Minted Hna 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_v118.