Tautomycetin (TMC) is a T cell-specific immunosuppressant with a unique ester bond linkage between a terminal cyclic anhydride and a linear polyketide chain. Since an afsR2 was proved to be a global antibiotics-stimulating regulatory gene in various Streptomyces species, an afsR2-induced TMC productivity stimulation was investigated in a TMC-producing Streptomyces sp. CK4412 strain. An afsR2 gene was cloned under the influence of a strong constitutive ermE* promoter in an integrative expression vector, followed by its conjugation into the Streptomyces sp. CK4412. Comparing TMC productivity and antifungal activity of the wild type and the afsR2-containing ex-conjugant revealed that afsR2 over-expression stimulated TMC production approximately 2.4-fold in Streptomyces sp. CK4412. Based on both RT-PCR and real-time RT-PCR analyses, an afsR2 over-expression significantly stimulated the expression of a TMC-specific positive regulatory gene, tmcN. This implies that the stimulatory effect of afsR2 functions in Streptomyces sp. CK4412 via up-regulation of a TMC pathway-specific positive regulatory gene over-expression. (C) 2009 Elsevier Ltd. All rights reserved.