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Co‐ordinated regulation of the extracytoplasmic stress factor, sigmaE, with other E scherichia coli sigma factors by (p)ppGpp and DksA may be achieved by specific regulation of individual holoenzymes
Author(s) -
Gopalkrishnan Saumya,
Nicoloff Herve,
Ades Sarah E.
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12674
Subject(s) - stringent response , sigma factor , biology , cell envelope , starvation , gene , microbiology and biotechnology , biochemistry , rna , escherichia coli , rna polymerase , endocrinology
Summary The E . coli alternative sigma factor, σ E , transcribes genes required to maintain the cell envelope and is activated by conditions that destabilize the envelope. σ E is also activated during entry into stationary phase in the absence of envelope stress by the alarmone (p)ppGpp . (p)ppGpp controls a large regulatory network, reducing expression of σ 70 ‐dependent genes required for rapid growth and activating σ 70 ‐dependent and alternative sigma factor‐dependent genes required for stress survival. The DksA protein often potentiates the effects of (p)ppGpp . Here we examine regulation of σ E by (p)ppGpp and DksA following starvation for nutrients. We find that (p)ppGpp is required for increased σ E activity under all conditions tested, but the requirement for DksA varies. DksA is required during amino acid starvation, but is dispensable during phosphate starvation. In contrast, regulation of σ S is (p)ppGpp ‐ and DksA ‐dependent under all conditions tested, while negative regulation of σ 70 is DksA ‐ but not (p)ppGpp ‐dependent during phosphate starvation, yet requires both factors during amino acid starvation. These findings suggest that the mechanism of transcriptional regulation by (p)ppGpp and/or DksA cannot yet be explained by a unifying model and is specific to individual promoters, individual holoenzymes, and specific starvation conditions.