P140: Heterologous Functional Expression of an Entire Biosynthetic Gene Cluster Encoding a Linear Polyketide, Tautomycetin in Streptomyces species

Tautomycetin (TMC) is a protein phosphatase PP1/PP2A inhibitor, which is also a pharmacokinetically-superior T-cell-specific immunosuppressant produced by Streptomyces sp. CK4412. TMC has a structurally-unique ester bond linkage between a terminal cyclic C8 dialkylmaleic anhydride moiety and linear polyketide chain bearing an unusual terminal alkene. TMC was also reported to possess anti-cancer activities against colorectal and tyroid cancer cells, implying that TMC could be a potentially-valuable immunosuppressive and anticancer drug lead compound. Recently, we isolated and characterized the entire TMC biosynthetic gene cluster from Streptomyces sp. CK4412 and demonstrated its identity by gene disruption analysis. As expected in other Streptomyces species, TMC production was observed to be extremely low due to multiple regulatory pathways operating with several layers of complicated control systems. As a promising alternative approach to improve the TMC titer, an entire TMC biosynthetic gene cluster (approximately 100 kb) from Streptomyces sp. CK4412 was cloned into a single pSBAC vector, followed by heterologous expression of this giant recombinant DNA in a couple of well-characterized Streptomyces strains such as S. lividans TK21 and S. coelicolor M145. Noticeable amounts of TMC were successfully detected from both recombinant Streptomyces liquid cultures, followed by quantitative analysis of the TMC titers among various Streptomyces strains. The more detailed results will be further discussed.