Transcription of Bacillus subtilis degR is sigma D dependent and suppressed by multicopy proB through sigma D.

Production of Bacillus subtilis exoproteases is positively regulated by the DegS-DegU two-component regulatory system and other regulatory factors including DegR and ProB. It was shown that the expression of degR was virtually abolished in a sigD mutant and that the transcriptional initiation site in vivo is preceded by a sequence very similar to the consensus sequence of sigma D-recognized promoters. Alteration of the -10 sequence of the putative promoter greatly reduced the expression of degR. These results show that degR expression is driven by the alternative sigma factor, sigma D. It was found that degR expression was suppressed by multiple copies of proB on plasmid pLC1 and that this suppression was exerted at the transcriptional level through a target in the vicinity of the degR promoter. Furthermore, it was shown that the expression of another sigma D-directed gene, hag, was suppressed by pLC1. Suppression by pLC1 diminished when the sequence of the -10 element of the degR promoter was changed to a sigma A-like promoter sequence. pLC1, however, did not suppress sigD expression. On the basis of these results, we conclude that multicopy proB on pLC1 inhibits transcription from sigma D-driven promoters by affecting some posttranscriptional process of sigma D.