Analysis of the Role of RsbV, RsbW, and RsbY in Regulating σ ^B Activity in Bacillus cereus

Abstract

The alternative sigma factor B is an important regulator of the stress response of Bacillus cereus. Here, the role of the regulatory proteins RsbV, RsbW, and RsbY in regulating B activity in B. cereus is analyzed. Functional characterization of RsbV and RsbW showed that they act as an anti-sigma factor antagonist and an anti-sigma factor, respectively. RsbW can also act as a kinase on RsbV. These data are in line with earlier functional characterizations of RsbV and RsbW homologs in B. subtilis. The rsbY gene is unique to B. cereus and its closest relatives and is predicted to encode a protein with an N-terminal CheY domain and a C-terminal PP2C domain. In an rsbY deletion mutant, the B response upon stress exposure was almost completely abolished, but the response could be restored by complementation with full-length rsbY. Expression analysis showed that rsbY is transcribed from both a A -dependent promoter and a B -dependent promoter. The central role of RsbY in regulating the activity of B indicates that in B. cereus, the B activation pathway is markedly different from that in other gram-positive bacteria.

Identification of the σBRegulon ofBacillus cereusand Conservation of σB-Regulated Genes in Low-GC-Content Gram-Positive Bacteria

“…However, under stress conditions, the phosphorylated form of RsbV can be dephosphorylated by the action of a PP2C-type phosphatase, which then leads to the formation of the RsbVRsbW complex and the activation of B (reviewed in references 17, 26, and 36). In the B. cereus group, the PP2C phosphatase RsbY appears to be the only phosphatase responsible for the activation of B under stress, as the deletion of the rsbY gene in B. cereus leads to an abolished B response under several stress conditions, including a heat shock (34).…”

orf4 of the Bacillus cereus sigB Gene Cluster Encodes a General Stress-Inducible Dps-Like Bacterioferritin

“…This mechanism is most likely employed in B. cereus, in which proteins encoded by the sigB cluster are known to be involved in the regulation of B activity, with the exception that the role of orf4 is currently unclear (46). Our data showed indistinguishable B activations upon 42°C heat stress for the wild-type strain and the orf4-null mutant, suggesting that orf4 is not involved in the regulation of B activity (Fig.…”

“…With a similar genetic organization, proteins encoded by the sigB cluster in B. cereus (Fig. 1A) have also been found to be involved in B activation, with the exception that the function of orf4 remains unclear (46). Therefore, we were interested in investigating whether orf4 participates in B regulation.…”

“…In B. cereus, B activity is controlled by the gene products encoded by the sigB cluster, which includes rsbV, rsbW, sigB, orf4, and rsbY. The roles of these genes have all been described, with the exception of the function of the fourth putative open reading frame, orf4 (GenBank accession number GI:29894703) (17,46). As orf4 is situated in the sigB cluster, it would be interesting to know whether orf4 is involved in B regulation.…”

The International Bacillus anthracis , B. cereus , and B. thuringiensis Conference, “ Bacillus -ACT05”

“…Transcriptome and proteome analyses indicate roles for these genes in biofilm formation, sporulation, and other stress responses (14,40). Van Schaik focused on the stress response sigma factor SigB.…”