Identification of DNA-binding proteins involved in regulation of expression of the Streptomyces aureofaciens sigF gene, which encodes sporulation sigma factor σF

摘要

Expression of the sigF gene encoding a sporulation-specific sigma factor, σF, in Streptomyces aureofaciens is restricted only to sporulation. Gel mobility-shift assays using protein fractions from different developmental stages of S. aureofaciens revealed two different putative proteins specifically bound to the sigF promoter region: a protein (designated RsfA) present in young substrate mycelium, and a protein (designated RsfB) present in the course of sporulation. Based on the characteristic profiles of their appearance during differentiation, RsfA might be a repressor and RsfB an activator of sigF expression. The location of a specific binding site of the repressor-like protein (RsfA) was determined by gel mobility-shift assays of promoter deletion fragments and by DNase I footprinting analysis. The binding site mapped from nucleotides ?87 to ?25 relative to the transcription start point of the sigF promoter, and overlapped the ?35 promoter region. Given the dependence of sigF expression upon whiH, the putative sporulation transcription factor WhiH was overproduced in Escherichia coli and used in the mobility-shift assays with the sigF promoter. However, no specific binding was detected, indicating an indirect dependence of sigF upon whiH.