Bacterial retrons encode phage-defending tripartite toxin-antitoxin systems.

ABSTRACT: Retrons are prokaryotic genetic retroelements encoding a reverse transcriptase that produces multi-copy single-stranded DNA¹ (msDNA). Despite decades of research on the biosynthesis of msDNA², the function and physiological roles of retrons have remained unknown. Here we show that Retron-Sen2 of Salmonella enterica serovar Typhimurium encodes an accessory toxin protein, STM14_4640, which we renamed as RcaT. RcaT is neutralized by the reverse transcriptase-msDNA antitoxin complex, and becomes active upon perturbation of msDNA biosynthesis. The reverse transcriptase is required for binding to RcaT, and the msDNA is required for the antitoxin activity. The highly prevalent RcaT-containing retron family constitutes a new type of tripartite DNA-containing toxin-antitoxin s

SUBMITTER: Bobonis J 

PROVIDER: S-EPMC11938430 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature