Utilization of one promoter by two forms of RNA polymerase from Bacillus subtilis

Bacillus subtilis possesses several forms of RNA polymerase, each differing in its sigma subunit and its specificity of promoter recognition. The sequential appearance of sigma subunits, which change the promoter recognition specificity of RNA polymerase, may have a key role in controlling the temporal pattern of gene expression required for endospore development in B. subtilis. Several genes that are expressed over relatively long periods of time during the developmental cycle are transcribed by more than one form of RNA polymerase, which initiate transcription from either tandem or overlapping promoter. The promoter region for the ctc gene is interesting because transcription is initiated at or near the same position by both sigma 37 RNA polymerase (E sigma 37), a minor form in growing cells, and sigma 29 RNA polymerase (E sigma 29), a form which appears approximately 2 h after the initiation of sproulation. Here we report that several base substitutions in the ctc promoter differentially affect the utilization of the promoter by E sigma 37 or E sigma 29.