Cross-interaction of anti-σH factor RshA with BldG, an anti-sigma factor antagonist in Streptomyces griseus


  • Editor: Skorn Mongkolsuk

Correspondence: Kenji Ueda, Life Science Research Center, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa 252-0880, Japan. Tel.: +81 466 84 3937; fax: +81 466 84 3935; e-mail:


Stress-response sigma factor σH is negatively regulated by its cognate anti-sigma factor RshA in Streptomyces griseus. As the overexpression of RshA in the wild-type strain confers a distinctive bald phenotype (deficiency in aerial mycelium formation and streptomycin production), RshA is supposed to associate with not only σH but also another regulatory element that plays a crucial role in the developmental control of S. griseus. Here, we show that an anti-sigma factor antagonist BldG associates with RshA and negatively regulates its activity. The bald phenotype conferred by the overexpression of rshA was restored to the wild-type phenotype by the coexpression with bldG. The in vivo and in vitro protein interaction analyses demonstrated the specific association between RshA and BldG. A bldG mutant exhibited a distinctive bald phenotype and was defective in the σH-dependent transcription activities. The positive regulatory role of BldG regarding the σH activity was verified by an in vitro transcriptional analysis, in which the inhibition of σH-dependent transcription by RshA was abolished by the addition of BldG in a dose-responsive manner. Overall, evidence suggests that BldG serves as a master switch for both stress-response and developmental gene expression based on its association with multiple anti-sigma factors in S. griseus.