Genetic evidence for interaction of sigma A with two promoters in Bacillus subtilis.

The specificity of promoter binding by RNA polymerase is governed by the sigma subunit. Recent studies, in which single-amino-acid substitutions in sigma factors have been found to suppress the effects of specific base pair substitutions in promoters, support the model that these sigma factors make sequence-specific contacts with nucleotides at the -10 and -35 regions of promoters. We found that single-amino-acid substitutions in the putative -35 region and -10 region recognition domains of sigma A specifically suppressed the effects of mutations in the -35 and -10 regions, respectively, of two promoters that are expressed in exponentially growing Bacillus subtilis. These mutations change the specificity of sigma A, the primary sigma factor in growing B. subtilis, and demonstrate that this sigma factor interacts with promoters in a manner similar to that of its homolog in Escherichia coli, sigma 70. These mutant derivatives of sigma A also provide a tool that may be useful for determining whether sigma A uses specific promoters in vivo.     

The genome of Bacillus subtilis phage SPP1: structure of an early promoter

The strongest of five 'early' promoters of Bacillus subtilis phage SPP1 was localized in a DNA restriction fragment by analysis of RNA polymerase binding and R-loop formation. The nucleotide sequence of the promoter region was established. The signal structures identified were similar to those recognized by the sigma 55 RNA polymerase of B. subtilis. The promoter precedes an open reading frame with 51 codons. A protein with the Mr predicted from the nucleotide sequence was identified in minicells.     

σ~(38)识别的启动子-35区核酸序列特征研究

依据部分资料假定大肠杆菌ＲＮＡ聚合酶的σ３８亚单位在特异启动子的－３５区识别的保守序列是－ＴＣＴＣＣＣ－,合成用其它碱基分别取代这一区域每一个碱基的引物,以ｏｓｍＹ基因片段为模板,通过ＰＣＲ扩增成－３５区含不同碱基序列的转录模板,用体外重组的由σ３８和核心酶（Ｅ）组成的全酶（Ｅσ３８）对这些启动子进行体外转录．结果显示含－ＴＣＴＣＣＣ－序列的启动子的转录水平既低于原始的ｏｓｍＹ启动子,又低于经ＰＣＲ扩增的其它序列．综合研究结果推测,这一区域的保守序列是－ＴＣＴＣＴＣ－．