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

Abstract

Bacillus subtilis possesses several forms of RNA polymerase, each differing in its σ subunit and its specificity of promoter recognition^1,2. The sequential appearance of σ 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. subtilis³. 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 promoters^2,4. The promoter region for the ctc gene is interesting because transcription is initiated at or near the same position by both σ³⁷ RNA polymerase (Eσ³⁷), a minor form in growing cells, and σ²⁹ RNA polymerase (Eσ²⁹), a form which appears ∼2 h after the initiation of sproulation⁵. Here we report that several base substitutions in the ctc promoter differentially affect the utilization of the promoter by Eσ³⁷ or Eσ²⁹.