Control of Sporulation Gene Expression in Bacillus subtilis by the Chromosome Partitioning Proteins Soj (ParA) and Spo0J (ParB)

Two chromosome partitioning proteins, Soj (ParA) and Spo0J (ParB), regulate the initiation of sporulation inBacillus subtilis . In aspo0J null mutant, sporulation is inhibited by the action of Soj. Soj negatively regulates expression of several sporulation genes by binding to the promoter regions and inhibiting transcription. All of the genes known to be inhibited by Soj are also activated by the phosphorylated form of the transcription factor Spo0A (Spo0A∼P). We found that, in aspo0J null mutant, Soj affected sporulation, in part, by decreasing the level of Spo0A protein. Soj negatively regulated transcription ofspo0A and associated with thespo0A promoter region in vivo. Expression ofspo0A from a heterologous promoter in aspo0J null mutant restored Spo0A levels and partly bypassed the sporulation and gene expression defects. Soj did not appear to significantly affect phosphorylation of Spo0A. Thus, in the absence of Spo0J, Soj inhibits sporulation and sporulation gene expression by inhibiting accumulation of the activator protein Spo0A and by acting downstream of Spo0A to inhibit gene expression directly.