Homologous pairs of regulatory proteins control activity of Bacillus subtilis transcription factor sigma(b) in response to environmental stress.
In Bacillus subtilis, activity of the general stress transcription factor sigma B is controlled posttranslationally by a regulatory network that transmits signals of environmental and metabolic stress. These signals include heat, ethanol, or osmotic challenge, or a sharp decrease in cellular energy levels, and all ultimately control sigma B activity by influencing the binding decision of the RsbW anti-sigma factor. In the absence of stress, RsbW binds to sigma B and prevents its association with RNA polymerase core enzyme. However, following stress, RsbW binds instead to the RsbV anti-anti-sigma factor, thereby releasing sigma B to direct transcription of its target genes. These two principal regulators of sigmaB activity are encoded in the eight-gene sigB operon, which has the gene order rsbR-rsbS-rsbT-rsbU-rsbV-rsbW-sig B-rsbX (where rsb stands for regulator of sigma B). Notably, the predicted rsbS product has significant amino acid identity to the RsbV anti-anti-sigma factor and the predicted rsbT product resembles the RsbW anti-sigma factor. To determine the roles of rsbS and rsbT, null or missense mutations were constructed in the chromosomal copies or each and tested for their effects on expression of a sigma B-dependent reporter fusion. On the basis of this genetic analysis, our principal conclusions are that (i) the rsbS product is a negative regulator of or" activity, (ii) the rsbT product is a positive regulator, (iii) RsbS requires RsbT for function, and (iv) the RsbS-RsbT and RsbV-RsbW pairs act hierarchically by a common mechanism in which key protein-protein interactions are controlled by phosphorylation events.
Kang
C M
CM
Department of Food Science and Technology, University of California, Davis 95616, USA.
Brody
M S
MS
Akbar
S
S
Yang
X
X
Price
C W
CW
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D004269:DNA, Bacterial; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D010641:Phenotype; D010766:Phosphorylation; D012808:Sigma Factor / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C079011:SigB protein, Bacteria; D012808:Sigma Factor; D014157:Transcription Factors