An updated evolutionary classification of CRISPR-Cas systems including rare variants.

ABSTRACT: The known diversity of CRISPR-Cas systems continues to expand. To encompass new discoveries, here we present an updated evolutionary classification of CRISPR-Cas systems. The updated CRISPR-Cas classification includes 2 classes, 7 types and 46 subtypes, compared with the 6 types and 33 subtypes in our previous survey 5 years ago. In addition, a classification of the cyclic oligoadenylate-dependent signalling pathway in type III systems is presented. We also discuss recently characterized alternative CRISPR-Cas functionalities, notably, type IV variants that cleave the target DNA and type V variants that inhibit the target replication without cleavage. Analysis of the abundance of CRISPR-Cas variants in genomes and metagenomes shows that the previously defined systems are relatively common,

SUBMITTER: Makarova KS 

PROVIDER: S-EPMC12669027 | biostudies-literature | 2025 Dec

REPOSITORIES: biostudies-literature