Genetic evidence that multiple proteases are involved in modulation of heat-induced activation of the sigma factor SigI in Bacillus subtilis.
The Bacillus subtilis sigI-rsgI operon encodes the heat-inducible sigma factor SigI and its cognate anti-sigma factor RsgI. The heat-activated SigI positively regulates expression of sigI itself and genes involved in cell wall homeostasis and heat resistance. It remains unknown which protease(s) may contribute to degradation of RsgI and heat-induced activation of SigI. In this study, we found that transcription of sigI from its σI-dependent promoter under heat stress was downregulated in a strain lacking the heat-inducible sigma factor SigB. Deletion of protease-relevant clpP, clpC or rasP severely impaired sigI expression during heat stress, whereas deletion of clpE partially impaired sigI expression. Complementation of mutations with corresponding intact genes restored sigI expression. In a null mutant of rsgI, SigI was activated and sigI expression was strongly upregulated during normal growth and under heat stress. In this rsgI mutant, further inactivation of rasP or clpE did not affect sigI expression, whereas further inactivation of clpP or clpC severely or partially impaired sigI expression. Spx negatively influenced sigI expression during heat stress. Possible implications are discussed. Given that clpC, clpP and spx are directly regulated by SigB, SigB appears to control sigI expression under heat stress via ClpC, ClpP and Spx.
Tai-Yen
TY
Liu
Shu-Hung
SH
Chu
Yi-Nei
YN
Hu
Jyun-Jhih
JJ
Wang
Gwo-Chyuan
GC
Shaw
D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D015536:Down-Regulation; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D018869:Heat-Shock Response; D006358:Hot Temperature; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; C079011:SigB protein, Bacteria; C422477:SigI protein, Bacillus subtilis; D012808:Sigma Factor; D010447:Peptide Hydrolases
heat stress response; regulated proteolysis; regulatory network