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Dual-specificity anti-sigma factor reinforces control of cell-type specific gene expression in Bacillus subtilis.

ABSTRACT: Gene expression during spore development in Bacillus subtilis is controlled by cell type-specific RNA polymerase sigma factors. ?Fand ?E control early stages of development in the forespore and the mother cell, respectively. When, at an intermediate stage in development, the mother cell engulfs the forespore, ?F is replaced by ?G and ?E is replaced by ?K. The anti-sigma factor CsfB is produced under the control of ?F and binds to and inhibits the auto-regulatory ?G, but not ?F. A position in region 2.1, occupied by an asparagine in ?G and by a glutamate in ?F, is sufficient for CsfB discrimination of the two sigmas, and allows it to delay the early to late switch in forespore gene expression. We now show that following engulfment completion, csfB is switched on in the mother cell under the control of ?K and that CsfB binds to and inhibits ?E but not ?K, possibly to facilitate the switch from early to late gene expression. We show that a position in region 2.3 occupied by a conserved asparagine in ?E and by a conserved glutamate in ?K suffices for discrimination by CsfB. We also show that CsfB prevents activation of ?G in the mother cell and the premature ?G-dependent activation of ?K. Thus, CsfB establishes negative feedback loops that curtail the activity of ?E and prevent the ectopic activation of ?G in the mother cell. The capacity of CsfB to directly block ?E activity may also explain how CsfB plays a role as one of the several mechanisms that prevent ?E activation in the forespore. Thus the capacity of CsfB to differentiate between the highly similar ?F/?G and ?E/?K pairs allows it to rinforce the cell-type specificity of these sigma factors and the transition from early to late development in B. subtilis, and possibly in all sporeformers that encode a CsfB orthologue.

SUBMITTER: Serrano M

PROVIDER: S-EPMC4383634 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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Dual-specificity anti-sigma factor reinforces control of cell-type specific gene expression in Bacillus subtilis.

Serrano Mónica M Gao JinXin J Bota João J Bate Ashley R AR Meisner Jeffrey J Eichenberger Patrick P Moran Charles P CP Henriques Adriano O AO

PLoS genetics 20150402 4

Gene expression during spore development in Bacillus subtilis is controlled by cell type-specific RNA polymerase sigma factors. σFand σE control early stages of development in the forespore and the mother cell, respectively. When, at an intermediate stage in development, the mother cell engulfs the forespore, σF is replaced by σG and σE is replaced by σK. The anti-sigma factor CsfB is produced under the control of σF and binds to and inhibits the auto-regulatory σG, but not σF. A position in reg ...[more]

PMID: 25835496

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Project description:RNA polymerase sigma factor sigma(F) initiates the prespore-specific program of gene expression during Bacillus subtilis sporulation. sigma(F) governs transcription of spoIIIG, encoding the late prespore-specific regulator sigma(G). However, transcription of spoIIIG is delayed relative to other genes under the control of sigma(F), and after synthesis, sigma(G) is initially kept in an inactive form. Activation of sigma(G) requires the complete engulfment of the prespore by the mother cell and expression of the spoIIIA and spoIIIJ loci. We screened for random mutations in spoIIIG that bypassed the requirement for spoIIIA for the activation of sigma(G). We found a mutation (spoIIIGE156K) that resulted in an amino acid substitution at position 156, which is adjacent to the position of a mutation (E155K) previously shown to prevent interaction of SpoIIAB with sigma(G). Comparative modelling techniques and in vivo studies suggested that the spoIIIGE156K mutation interferes with the interaction of SpoIIAB with sigma(G). The sigma(GE156K) isoform restored sigma(G)-directed gene expression to spoIIIA mutant cells. However, expression of sspE-lacZ in the spoIIIA spoIIIGE156K double mutant was delayed relative to completion of the engulfment process and was not confined to the prespore. Rather, beta-galactosidase accumulated throughout the entire cell at late times in development. This suggests that the activity of sigma(GE156K) is still regulated in the prespore of a spoIIIA mutant, but not by SpoIIAB. In agreement with this suggestion, we also found that expression of spoIIIGE156K from the promoter for the early prespore-specific gene spoIIQ still resulted in sspE-lacZ induction at the normal time during sporulation, coincidently with completion of the engulfment process. In contrast, transcription of spoIIIGE156K, but not of the wild-type spoIIIG gene, from the mother cell-specific spoIID promoter permitted the rapid induction of sspE-lacZ expression. Together, the results suggest that SpoIIAB is either redundant or has no role in the regulation of sigma(G) in the prespore.

Dataset Information

Dual-specificity anti-sigma factor reinforces control of cell-type specific gene expression in Bacillus subtilis.

Publications

Dual-specificity anti-sigma factor reinforces control of cell-type specific gene expression in Bacillus subtilis.

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