L-tryptophan and copper interactions linked to reduced colibactin genotoxicity in .

Unlabelled: Colibactin, a nonribosomal peptide/polyketide produced by , is a virulence factor and putative carcinogen that damages DNA by interstrand crosslinking (ICL). While the genes for colibactin biosynthesis have been identified, studies are needed to elucidate the mechanisms regulating colibactin production and activity. Here we perform untargeted metabolomics of coli cultures to identify L-tryptophan as a candidate repressor of colibactin activity. When is grown in a minimal medium supplemented with L-tryptophan ICL of plasmid DNA is reduced by >80%. L-tryptophan does not affect the transcription of genes but protects from copper toxicity and triggers the expression of genes to export copper to the periplasm where copper can directly inhibit the ClbP peptidase domain. Thus, L-tryptophan and copper interact and repress colibactin activity, potentially reducing its carcinogenic effects in the intestine.

Importance: Colibactin is a small molecule produced by + that damages DNA, leading to oncogenic mutations in human genomes. Colibactin-producing (+) cells promote tumorigenesis in mouse models of colorectal cancer (CRC) and are elevated in abundance in CRC patient biopsies, making it important to identify the regulatory systems governing colibactin production. Here, we apply a systems biology approach to explore metabolite repression of colibactin production in + . We identify L-tryptophan as a repressor of colibactin genotoxicity that stimulates the expression of genes to export copper to the periplasm where it can inhibit ClbP, the colibactin-activating peptidase. These results work toward an antibiotic-sparing, prophylactic strategy to inhibit colibactin genotoxicity and its tumorigenic effects in the intestine.