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J. Bacteriol., Jul 1996, 3846-3853, Vol 178, No. 13
CM Kang, MS Brody, S Akbar, X Yang and CW Price
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.
Copyright © 1996, American Society for Microbiology
Homologous pairs of regulatory proteins control activity of Bacillus subtilis transcription factor sigma(b) in response to environmental stress
Department of Food Science and Technology, University of California, Davis 95616, USA.
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