Evidence that the transcriptional activator Spo0A interacts with two sigma factors in Bacillus subtilis

1 July 1995

journal article
Published by Wiley in Molecular Microbiology

Vol. 17 (2) , 281-290
https://doi.org/10.1111/j.1365-2958.1995.mmi_17020281.x

Abstract

The transcriptional regulator Spo0A activates transcription from two types of promoters. One type of promoter is used by RNA polymerase containing τ^A, whereas the other type is used by RNA polymerase containing τ^H. There are Spo0A‐binding sites near the −35 region of both types of promoters. It has been reported that some transcriptional regulators that bind near the −35 regions of promoters directly interact with the sigma subunit of RNA polymerase. Therefore, we looked for evidence that Spo0A interacts with both sigma factors by searching for single amino acid substitutions in these factors that specifically prevent expression from Spo0A‐dependent promoters, but that do not decrease activity of Spo0A‐independent promoters. Two such amino acid substitutions were isolated in τ^A and one was isolated in τ^H. The amino acid substitutions in τ^A prevented expression from the Spo0A‐activated promoters, spoIIG and spoIIE, but expression was not impaired from the Spo0A‐independent, τ^A‐dependent promoter tms or from the Spo0A‐activated, τ^H‐dependent promoter, spoIIA. The amino acid substitution in τ^H prevented expression from the spoIIA promoter but not from the Spo0A‐independent promoter, citGp2, which is used by τ^H‐RNA polymerase. All of these amino acid substitutions occur in the carboxyl terminus of the sigma factors. These amino acid substitutions may define the sites of contact between the sigma factors and Spo0A. The ability of response regulators such as Spo0A to interact with multiple sigma factors may increase the variety of responses made by bacteria using a limited number of transcription factors.

Keywords

SIGMA FACTOR

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