Publication Date:
2013-07-11
Description:
Background: Transcriptional regulation by alternative sigma (sigma) factors represents an important mechanism that allows bacteria to rapidly regulate transcript and protein levels in response to changing environmental conditions. While the role of the alternative sigma factor sigmaB has been comparatively well characterized in L. monocytogenes, our understanding of the roles of the three other L. monocytogenes alternative sigma factors is still limited. In this study, we employed a quantitative proteomics approach using Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) to characterize the L. monocytogenes sigmaL, sigmaH, and sigmaC protein regulons. Proteomic comparisons used a quadruple alternative sigma factor mutant strain (DeltaBCHL) and strains expressing a single alternative sigma factor (i.e., sigmaL, sigmaH, and sigmaC; strains DeltaBCH, DeltaBCL, and DeltaBHL) to eliminate potential redundancies between sigma factors. Results: Among the three alternative sigma factors studied here, sigmaH provides positive regulation for the largest number of proteins, consistent with previous transcriptomic studies, while sigmaL appears to contribute to negative regulation of a number of proteins. sigmaC was found to regulate a small number of proteins in L. monocytogenes grown to stationary phase at 37[degree sign]C. Proteins identified as being regulated by multiple alternative sigma factors include MptA, which is a component of a PTS system with a potential role in regulation of PrfA activity. Conclusions: This study provides initial insights into global regulation of protein production by the L. monocytogenes alternative sigma factors sigmaL, sigmaH, and sigmaC. While, among these sigma factors, sigmaH appears to positively regulate the largest number of proteins, we also identified PTS systems that appear to be co-regulated by multiple alternative sigma factors. Future studies should not only explore potential roles of alternative sigma factors in activating a "cascade" of PTS systems that potentially regulate PrfA, but also may want to explore the sigmaL and sigmaC regulons under different environmental conditions to identify conditions where these sigma factors may regulate larger numbers of proteins or genes.
Electronic ISSN:
1471-2180
Topics:
Biology
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