Back to Search
Start Over
A Negative Feedback Loop That Limits the Ectopic Activation of a Cell Type-Specific Sporulation Sigma Factor of Bacillus subtilis.
- Source :
- PLoS Genetics; Sep2011, Vol. 7 Issue 9, Special section p1-16, 16p
- Publication Year :
- 2011
-
Abstract
- Two highly similar RNA polymerase sigma subunits, σ<superscript>F</superscript> and σ<superscript>G</superscript>, govern the early and late phases of forespore-specific gene expression during spore differentiation in Bacillus subtilis. σ<superscript>F</superscript> drives synthesis of σ<superscript>G</superscript> but the latter only becomes active once engulfment of the forespore by the mother cell is completed, its levels rising quickly due to a positive feedback loop. The mechanisms that prevent premature or ectopic activation of σ<superscript>G</superscript> while discriminating between σ<superscript>F</superscript> and σ<superscript>G</superscript> in the forespore are not fully comprehended. Here, we report that the substitution of an asparagine by a glutamic acid at position 45 of σ<superscript>G</superscript> (N45E) strongly reduced binding by a previously characterized anti-sigma factor, CsfB (also known as Gin), in vitro, and increased the activity of σ<superscript>G</superscript> in vivo. The N45E mutation caused the appearance of a sub-population of pre-divisional cells with strong activity of σ<superscript>G</superscript>. CsfB is normally produced in the forespore, under σ<superscript>F</superscript> control, but sigGN45E mutant cells also expressed csfB and did so in a σ<superscript>G</superscript>-dependent manner, autonomously from σ<superscript>F</superscript>. Thus, a negative feedback loop involving CsfB counteracts the positive feedback loop resulting from ectopic σ<superscript>G</superscript> activity. N45 is invariant in the homologous position of σ<superscript>G</superscript> orthologues, whereas its functional equivalent in σ<superscript>F</superscript> proteins, E39, is highly conserved. While CsfB does not bind to wildtype σ<superscript>F</superscript>, a E39N substitution in σ<superscript>F</superscript> resulted in efficient binding of CsfB to σ<superscript>F</superscript>. Moreover, under certain conditions, the E39N alteration strongly restrains the activity of sF in vivo, in a csfB-dependent manner, and the efficiency of sporulation. Therefore, a single amino residue, N45/E39, is sufficient for the ability of CsfB to discriminate between the two foresporespecific sigma factors in B. subtilis. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 15537390
- Volume :
- 7
- Issue :
- 9
- Database :
- Complementary Index
- Journal :
- PLoS Genetics
- Publication Type :
- Academic Journal
- Accession number :
- 66347624
- Full Text :
- https://doi.org/10.1371/journal.pgen.1002220