bioRxiv2019
Colibactin is an as-yet-uncharacterized human gut bacterial genotoxin, whose biosynthesis is linked to clb genomic island that distributes widespread in pathogenic and commensal human enterobacteria. Colibactin-producing gut microbes promote colon tumor formation and enhance progression of colorectal cancer (CRC) via DNA double-strand breaks (DSBs)-induced cellular senescence and death; however, the chemical basis contributing to the pathogenesis at the molecular level remains elusive. Here we report the discovery and the mechanism of action of colibactin-645 as the highly sought final colibactin metabolite with a novel molecular scaffold. Colibactin-645 recapitulates its previously assumed genotoxicity and cytotoxicity, exhibiting a strong DNA DSBs activity in vitro and in human cell cultures via a unique copper-mediated oxidative mechanism. We also present a complete model for colibactin biosynthesis, revealing an unprecedented dual function of the aminomalonate-utilizing polyketide synthases. This work thus provides the first molecular basis for colibactins genotoxic activity and facilitates further mechanistic study of colibactin-related CRC incidence and prevention.