The Bacillus subtilis response regulator gene degU is positively 1 regulated by CcpA and by catabolite - repressed synthesis of 2 ClpC 3

19 20 In Bacillus subtilis, the response regulator DegU and its cognate kinase DegS constitute a 21 two-component system that regulates many cellular processes, including exoprotease 22 production and genetic competence. Phosphorylated DegU (DegU-P) activates its own 23 promoter and is degraded by the ClpCP protease. We observed induction of degU by 24 glucose in sporulation medium. This was abolished in two mutants: the ccpA (catabolite 25 control protein A) and clpC disruptants. Transcription of the promoter of the operon 26 containing clpC (PclpC) decreased in the presence of glucose, and the disruption of ccpA 27 resulted in derepression of PclpC. However, this would not be directly mediated by CcpA, 28 because we failed to detect binding of CcpA to PclpC. Glucose decreased the expression 29 of clpC, leading to low cellular concentrations of the ClpCP protease. Thus, degU is 30 induced through activation of autoregulation by decrease in ClpCP-dependent proteolysis 31 of DegU-P. An electro-mobility shift assay showed that CcpA directly bound to the degU 32 upstream region, indicating that CcpA activates degU through binding. The bound region 33 was narrowed down to 27 bases, which contained a cre (catabolite responsive element) 34 sequence with a low match to the cre consensus sequence. In a footprint analysis, CcpA 35 specifically protected a region containing the cre sequence from DNase I digestion. The 36 induction of degU by glucose showed complex regulation of the degU gene. 37 38 on O cber 8, 2017 by gest http/jb.asm .rg/ D ow nladed fom