ABSTRACT
During a search by computer-aided inspection of two-dimensional (2D) protein gels for ςB-dependent general stress proteins exhibiting atypical induction profiles, a protein initially called Hst23 was identified as a product of the yvyD gene of Bacillus subtilis. In addition to the typical ςB-dependent, stress- and starvation-inducible pattern,yvyD is also induced in response to amino acid depletion. By primer extension of RNA isolated from the wild-type strain and appropriate mutants carrying mutations in the sigB and/orspo0H gene, two promoters were mapped upstream of theyvyD gene. The ςB-dependent promoter drives expression of yvyD under stress conditions and after glucose starvation, whereas a ςH-dependent promoter is responsible for yvyD transcription following amino acid limitation. Analysis of Northern blots revealed that yvyDis transcribed monocistronically and confirmed the conclusions drawn from the primer extension experiments. The analysis of the protein synthesis pattern in amino acid-starved wild-type and relAmutant cells showed that the YvyD protein is not synthesized in therelA mutant background. It was concluded that the stringent response plays a role in the activation of ςH. TheyvyD gene product is homologous to a protein which might modify the activity of ς54 in gram-negative bacteria. The expression of a ςL-dependent (ςL is the equivalent of ς54 in B. subtilis)levD-lacZ fusion is upregulated twofold in ayvyD mutant. This indicates that the yvyD gene product, being a member of both the ςB and ςH regulons, might negatively regulate the activity of the ςL regulon. We conclude that (i) systematic, computer-aided analysis of 2D protein gels is appropriate for the identification of genes regulated by multiple transcription factors and that (ii) YvyD might form a junction between the ςB and ςH regulons on one side and the ςL regulon on the other.
Initiation of Bacillus subtilis sporulation by the stringent response to partial amino acid deprivation.
