IDENTIFICATION OF TARGET PROMOTERS FOR THE BACILLUS-SUBTILIS SIGMA(X)FACTOR USING A CONSENSUS-DIRECTED SEARCH

The promoter selectivity of RNA polymerase (RNAP) can be altered by th e association with alternative sigma subunits. Bacillus subtilis hosts a multitude of sigma factors,several of which coordinate the complex developmental program culminating in endo,spore formation. Genome sequ encing has revealed an unanticipated seven new sigma factors of the hi ghly divergent extracytoplasmic function (ECF) sub-family. Virtually n oticing is known regarding either the promoter selectivity or the targ et genes for these newly identified sigma factors. We have used satura tion mutagenesis to define a promoter consensus for recognition by one such ECF sigma factor, sigma(X). The resulting consensus sequence was used to identify candidate sigma(X) target sites. Three newly identif ied sigma(X)-dependent promoters precede genes encoding regulatory pro teins: an AbrB homolog (Abh), a putative response regulator aspartate phosphatase (RapD), and a regulator of autolysin expression (LytR). si gma(X) also contributes to the expression of CsbB, a putative membrane -bound glucosyl transferase that is partially controlled by the sigma( B) stress response sigma factor. Since LytR modulates the expression o f the major autolytic amidase and CsbB may function in peptidoglycan s ynthesis or modification, we suggest that sigma(X) participates in the regulation of peptidoglycan synthesis and turnover. (C) 1998 Academic Press Limited.