a negative feedback loop that limits the ectopic activation of a cell type–specific sporulation sigma factor of bacillus subtilis负面的反馈回路,限制了细胞的异位激活特定类型的枯草芽孢杆菌孢子形成σ因子.pdfVIP

A Negative Feedback Loop That Limits the Ectopic Activation of a Cell Type–Specific Sporulation Sigma Factor of Bacillus subtilis ´ 1 1. 1.¤ 2 3 Monica Serrano , Gonc¸alo Real , Joana Santos , Jorge Carneiro , Charles P. Moran Jr. , Adriano O. Henriques1* ´ ´ ˆ 1 Instituto de Tecnologia Quımica e Biologica, Universidade Nova de Lisboa, Oeiras, Portugal, 2 Instituto Gulbenkian de Ciencia, Oeiras, Portugal, 3 Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, United States of America Abstract F G Two highly similar RNA polymerase sigma subunits, s and s , govern the early and late phases of forespore-specific gene expression during spore differentiation in Bacillus subtilis. sF drives synthesis of sG but the latter only becomes active once engulfment of the forespore by the mother cell is completed, its levels rising quickly due to a positive feedback loop. The mechanisms that prevent premature or ectopic activation of sG while discriminating between sF and sG in the forespore are not fully comprehended. Here, we report that the substitution of an asparagine by a glutamic acid at position 45 of sG (N45E) strongly reduced binding by a previously characterized anti-sigma factor, CsfB (also known as Gin), in vitro, and increased the activity of sG in vivo. The N45E mutation caused the appearance of a sub-population of pre-divisional cells with strong