SPO0A ACTIVATES AND REPRESSES ITS OWN SYNTHESIS BY BINDING AT ITS DUAL PROMOTERS

The Spo0A protein of Bacillus subtilis controls the onset of sporulation by regulating transcription of various genes in both positive and negative manners depending on the promoters affected. The expression of the spo0A gene occurs from two promoters (P(v),P(s)), separated by 148 bp, and transcription switches from P(v) to P(s) early in the sporulation program. DNase I footprint analysis of the spo0A promoter region revealed three distinct sites of Spo0A binding: -4 to +19 relative to P(v), -17 to +1 relative to P(s), and a region between P(v) and P(s). The P(v) region and the region between the two promoters was sufficient for repression of P(v). Induction of P(s) also required these regions which are upstream of -52 relative to P(s). Mutant Spo0A proteins containing asp-->asn mutations at asp10 and asp56 were inactive in repression of the abrB promoter in vivo yet still retained DNA-binding activity. The results presented are consistent with a model in which the phosphorylated form of Spo0A acts directly at its promoters to achieve induction of P(s) and repression of P(v). These effects at the spo0A promoter were independent of the presence of the major kinase, KinA.