title: Loss-of-function mutations in yjbD result in ClpX- and ClpP-independent competence development of Bacillus subtilis.
abstract: Mutations in clpP and clpX have pleiotropic effects on growth and developmentally regulated gene expression in Bacillus subtilis. ClpP and ClpX are needed for expression of comK, encoding the competence transcription factor required for the expression of genes within the competence regulon. ClpP, in combination with the ATPase ClpC, degrades the inhibitor of ComK, MecA. Proteolysis of MecA is stimulated by a small protein, ComS, which interacts with MecA. Suppressor mutations (cxs) were isolated that bypass the requirement for clpX for comK expression. These were found also to overcome the defect in comK expression conferred by a clpP mutation. These mutations were identified as missense mutations (cxs-5, -7 and -12) and a nonsense (UAG) codon substitution (cxs-10) in the yjbD coding sequence in a locus linked to mecA. That a yjbD disruption confers the cxs phenotype, together with its complementation by an ectopically expressed copy of yjbD, indicated that the suppressor alleles bear recessive, loss-of-function mutations of yjbD. ClpP- and ClpX-independent comK expression rendered by inactivation of yjbD was still medium-dependent and required ComS. MecA levels in a clpP-yjbD mutant were lower that those of clpP mutant cells and ComK protein concentration in the clpP mutant was restored to wild-type levels by the yjbD mutation. Consequently, the yjbD mutation bypasses the defect in competence development conferred by clpP and clpX. YjbD protein is barely detectable in wild-type cells, but is present in large amounts in the clpP mutant cells. The results suggest that the role of ClpP in competence development is to degrade YjbD protein so that ComS can productively interact with the MecA-ClpC-ComK complex. Alternatively, the result could suggest that YjbD has a negative effect on regulated proteolysis and that MecA is degraded independently of ClpP when YjbD is absent.
authors.affiliation: Department of Biochemistry and Molecular Biology, OGI School of Science and Engineering, Oregon Health and Science University, Beaverton, OR 97006-8921, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Nakano
authors.forename: F
authors.initials: F
authors.lastname: Hajarizadeh
authors.forename: Y
authors.initials: Y
authors.lastname: Zhu
authors.forename: P
authors.initials: P
authors.lastname: Zuber
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D049071:Endopeptidase Clp; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D006358:Hot Temperature; D018832:Molecular Chaperones; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D020161:Physical Chromosome Mapping; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D013171:Spores, Bacterial; D013489:Suppression, Genetic / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D014157:Transcription Factors; C083616:mecA protein, Bacillus subtilis; C087449:comK protein, Bacillus subtilis; D012697:Serine Endopeptidases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities