The Bacillus subtilisResponse Regulator Spo0A Stimulates Transcription of the spoIIGOperon through Modification of RNA Polymerase Promoter Complexes

Abstract

Sporulation in Bacillus subtilisis dependent on the response regulator Spo0A, which both represses and activates transcription in vitro. The activity of Spo0A is increased by phosphorylation. We previously demonstrated that the phosphorylation increased the ability of Spo0A to stimulate in vivotranscription from the promoter for the spoIIGoperon, one of the operons known to be regulated by Spo0A in vivo. In the work reported here we have examined the kinetics of transcription initiation at the spoIIGoperon promoter using a single round transcription assay and the kinetics of formation of spoIIGpromoter – RNA polymerase complexes using DNase I footprinting. Both the kinetic assays and the footprint assays indicated that the initial binding of the polymerase to the template was not dependent on the presence of Spo0A. The phosphorylated form of Spo0A stimulated the rate of initiation by affecting a step that occurred after the initial interaction of the polymerase with the template. Phosphorylation of Spo0A may stimulate transcription by modifying preinitiation complexes containing the polymerase and the promoter.