Identification and Characterization of wblA-dependent tmcT Regulation during Tautomycetin Biosynthesis in Streptomyces sp. CK4412

초록

Tautomycetin (TMC) is an unusual linear polyketide compound esterified with a cyclic anhydride. It exhibits novel activated T cell-specific immunosuppressant as well as anti-cancer activities. Previously, we isolated and characterized the entire TMC biosynthetic gene cluster from Streptomyces sp. CK4412, including a TMC pathway-specific gene, tmcN, the over-expression of which led to a significant increase in TMC productivity. In addition, we also reported that wblA acts as a global down-regulator of antibiotic biosynthesis through pathway-specific regulation in Streptomyces species. Here, we confirm that tmcT acts as another TMC pathway-specific regulatory gene within the TMC biosynthetic cluster. Specifically, tmcT deletion resulted in the complete loss of TMC production, whereas complementation with a tmcT-carrying integrative plasmid significantly restored TMC biosynthesis. We also identified a 0.39 kb wblA ortholog (named wblAtmc) from Streptomyces sp. CK4412 via genomic DNA library screening that showed 96% amino acid identity compared to a previously-known S. coelicolor wblA. Targeted gene disruption of wblAtmc in Streptomyces sp. CK4412 exhibited approximately 3-fold higher TMC productivity than that in the wild-type strain. Moreover, transcript analyses of the TMC biosynthetic and regulatory genes revealed that the expression of tmcT was strongly down-regulated by wblAtmc. These results imply that the TMC biosynthetic regulation network is controlled by two pathway-specific positive regulatory genes, wblAtmc-dependent tmcT as well as wblAtmc-independent tmcN in Streptomyces sp. CK4412.