Brig1 system

traitmech:000307 · CLASS · PROPOSED

A phage defense system in which an organism possesses a brig1-family locus whose encoded DNA glycosylase can excise alpha-glucosyl-hydroxymethylcytosine nucleobases from T-even bacteriophage DNA, generate abasic sites, and inhibit viral DNA replication.

Trait evidence (9)

DOI:10.1038/s41586-024-07329-9
Following this approach, we identified Brig1, a DNA glycosylase that excises α-glucosyl-hydroxymethylcytosine nucleobases from the bacteriophage T4 genome to generate abasic sites and inhibit viral replication

Hallinan et al. identify Brig1 as a phage DNA-targeting DNA glycosylase.
DOI:10.1038/s41586-024-07329-9
Brig1 homologues that provide immunity against T-even phages are present in multiple phage defence loci across distinct clades of bacteria

Hallinan et al. support modelling Brig1 as a bacterial phage-defence locus family rather than as one cloned environmental DNA insert.
DOI:10.1038/s41586-024-07329-9
This result demonstrates that gene c not only inhibits T4 DNA replication but also causes a slight and gradual depletion of the phage DNA within the infected population

Hallinan et al. connect the gene later named brig1 to inhibited T4 DNA replication in infected cells.
DOI:10.1038/s41586-024-07329-9
We named this gene bacteriophage replication inhibition DNA glycosylase 1 (brig1)

Hallinan et al. explicitly expand brig1 as bacteriophage replication inhibition DNA glycosylase 1.
DOI:10.1038/s41586-024-07329-9
Together, these data demonstrate that Brig1 targets α-glucosylated hmC nucleobases in the viral DNA to provide defence against T4

Hallinan et al. show that Brig1 defense is specific to alpha-glucosylated hydroxymethylcytosine in phage DNA.
DOI:10.1038/s41586-024-07329-9
Together, these results demonstrate that Brig1 is a DNA glycosylase that excises α-glucosyl-hmC nucleobases from ssDNA to generate abasic sites

Hallinan et al. directly verify that Brig1 DNA glycosylase activity creates abasic sites on alpha-glucosyl-hmC-containing substrates.
https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md
Brig1 | 10\.1038/s41586-024-07329-9 | DNA glycosylases provide antiviral defence in prokaryotes

The DefenseFinder article registry maps the named Brig1 model namespace to the Hallinan et al. Brig1 DNA-glycosylase paper.
https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md
| Brig1__Brig1 | | Brig1 | Custom | 20 |

The DefenseFinder HMM inventory records Brig1__Brig1 under the Brig1 model namespace.
https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md
| Brig1__ADP_ribosyl | | Brig1 | Custom | 20 |

The DefenseFinder HMM inventory records Brig1__ADP_ribosyl under the Brig1 model namespace.

Brig1 loci restrict T-even phage propagation

Conservative locus-level sketch linking a brig1-family DefenseFinder locus to halted T4-like phage replication, restricted T-even phage propagation, and the Brig1 phage-defense-system trait.

NONMECHANISTIC · The graph captures Brig1 as a named DefenseFinder DNA-glycosylase phage-defense system at locus level and deliberately defers a protein-resolved glycosylase mechanism. Hallinan et al. characterized the prototype Brig1 DNA glycosylase, alpha-glucosyl-hmC base excision, and abasic-site generation, but the natural host, accession-level Brig1-family proteins, broader substrate specificity, and the relationship of the DefenseFinder Brig1__ADP_ribosyl profile to characterized Brig1 activity remain unresolved.

Edge evidence

brig1 locus contributes to halted phage replication RO:0002326
Expression of the gene later named brig1 inhibits T4 phage DNA replication, and DefenseFinder catalogs Brig1 profiles for Brig1-family loci.
- DOI:10.1038/s41586-024-07329-9 gene c not only inhibits T4 DNA replication but also causes a slight and gradual depletion of the phage DNA within the infected population Hallinan et al. connect brig1 expression to inhibited T4 DNA replication in infected cells.
- https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md | Brig1__Brig1 | | Brig1 | Custom | 20 | The DefenseFinder HMM inventory records Brig1__Brig1 under the Brig1 model namespace.
halted phage replication contributes to restricted phage propagation RO:0002326
Brig1-associated inhibition of T4-like phage replication restricts T-even phage propagation after infection.
- DOI:10.1038/s41586-024-07329-9 Following this approach, we identified Brig1, a DNA glycosylase that excises α-glucosyl-hydroxymethylcytosine nucleobases from the bacteriophage T4 genome to generate abasic sites and inhibit viral replication. Brig1 homologues that provide immunity against T-even phages are present in multiple phage defence loci across distinct clades of bacteria Hallinan et al. connect Brig1-associated T4 replication inhibition to the broader Brig1-family T-even immunity phenotype.
restricted phage propagation confers Brig1 system METPO:2007700
Restriction of T-even phage propagation realizes the Brig1 system trait.
- DOI:10.1038/s41586-024-07329-9 Brig1 homologues that provide immunity against T-even phages are present in multiple phage defence loci across distinct clades of bacteria Hallinan et al. frame Brig1 homologues as a bacterial phage-defense locus family.
- https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md Brig1 | 10\.1038/s41586-024-07329-9 | DNA glycosylases provide antiviral defence in prokaryotes The DefenseFinder article registry maps the named Brig1 model namespace to the Hallinan et al. Brig1 DNA-glycosylase paper.
Brig1 system is a phage defense system rdfs:subClassOf
Brig1 system possession is a phage-defense-system trait.
- DOI:10.1038/s41586-024-07329-9 Brig1, a previously unknown anti-phage defence system with homologues across distinct clades of bacteria The Hallinan et al. editor summary places Brig1 in the anti-phage defense system class.

Provenance

Identifier source: TraitMech local identifier
Definition source: DOI:10.1038/s41586-024-07329-9

Parent traits (1)

phage defense system traitmech:000209

Synonyms (2)

Brig1 RELATED_SYNONYM · DOI:10.1038/s41586-024-07329-9
bacteriophage replication inhibition DNA glycosylase 1 RELATED_SYNONYM · DOI:10.1038/s41586-024-07329-9

kg-microbe context

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

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 natural Brig1 host taxa, broader Brig1-family specificity, and the Brig1__ADP_ribosyl DefenseFinder profile before minting narrower Brig1 children, adding canonical examples, or curating the protein-resolved glycosylase mechanism.

KNOWLEDGE GAP OPEN brig1-natural-host-and-profile-gap · raised by codex · 2026-09-20

Attached to causal_graphs#brig1_locus_restricts_t_even_phages

Hallinan et al. functionally isolated the first brig1 gene from a soil metagenomic fragment rather than a sequenced natural isolate, and they showed that experimentally tested Brig1 homologues can protect against T-even phages. The first TraitRecord therefore covers Brig1-family antiphage DNA-glycosylase-system possession at locus level while leaving natural host exemplars, accession-level Brig1-family proteins, the protein-grounded glycosylase mechanism, the full sequence-level system architecture, and the relationship between the DefenseFinder Brig1__Brig1 and Brig1__ADP_ribosyl profiles to separate subtype review.

Evidence

DOI:10.1038/s41586-024-07329-9
To uncover novel anti-phage defence systems present in unsequenced bacterial genomes, we screened an eDNA library generated in an earlier study
https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md
| Brig1__ADP_ribosyl | | Brig1 | Custom | 20 |

Curation history

2026-09-20T10:37:00Z · MINTED_TRAITMECH_ID · codex
Minted Brig1 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_v184.
2026-09-20T11:12:00Z · ADDRESSED_PR_REVIEW · codex
Resolved PR #1130 review issues #1131, #1132, #1133, and #1134 by narrowing the Brig1 graph to a locus-level DefenseFinder sketch, quoting the brig1 naming sentence, removing weak edge evidence, and reusing halted phage replication instead of adding a singleton replication node.