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Stress sigma factor RpoS degradation and translation are sensitive to the state of central metabolism.

ABSTRACT: RpoS, the stationary phase/stress sigma factor of Escherichia coli, regulates a large cohort of genes important for the cell to deal with suboptimal conditions. Its level increases quickly in the cell in response to many stresses and returns to low levels when growth resumes. Increased RpoS results from increased translation and decreased RpoS degradation. Translation is positively regulated by small RNAs (sRNAs). Protein stability is positively regulated by anti-adaptors, which prevent the RssB adaptor-mediated degradation of RpoS by the ClpXP protease. Inactivation of aceE, a subunit of pyruvate dehydrogenase (PDH), was found to increase levels of RpoS by affecting both translation and protein degradation. The stabilization of RpoS in aceE mutants is dependent on increased transcription and translation of IraP and IraD, two known anti-adaptors. The aceE mutation also leads to a significant increase in rpoS translation. The sRNAs known to positively regulate RpoS are not responsible for the increased translation; sequences around the start codon are sufficient for the induction of translation. PDH synthesizes acetyl-CoA; acetate supplementation allows the cell to synthesize acetyl-CoA by an alternative, less favored pathway, in part dependent upon RpoS. Acetate addition suppressed the effects of the aceE mutant on induction of the anti-adaptors, RpoS stabilization, and rpoS translation. Thus, the bacterial cell responds to lowered levels of acetyl-CoA by inducing RpoS, allowing reprogramming of E. coli metabolism.

SUBMITTER: Battesti A

PROVIDER: S-EPMC4413282 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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Stress sigma factor RpoS degradation and translation are sensitive to the state of central metabolism.

Battesti Aurelia A Majdalani Nadim N Gottesman Susan S

Proceedings of the National Academy of Sciences of the United States of America 20150406 16

RpoS, the stationary phase/stress sigma factor of Escherichia coli, regulates a large cohort of genes important for the cell to deal with suboptimal conditions. Its level increases quickly in the cell in response to many stresses and returns to low levels when growth resumes. Increased RpoS results from increased translation and decreased RpoS degradation. Translation is positively regulated by small RNAs (sRNAs). Protein stability is positively regulated by anti-adaptors, which prevent the RssB ...[more]

PMID: 25847996

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Project description:RpoS is a key stress-inducible sigma factor that regulates stress resistance genes in Escherichia coli, such as the katE gene encoding catalase HPII and the glg genes encoding glycogen synthesis proteins. Monitoring RpoS activity can provide information on the stress sensitivity of E. coli isolates in clinical settings because the RpoS in these isolates is often mutated. In the present study, we found a novel, missense point mutation at RpoS residue 128 in a clinical Shiga toxin-producing E. coli (STEC) isolate. This mutation caused RpoS dysfunction and increased stress sensitivity. A mutant rpoS was cloned from a clinical STEC that is vulnerable to cold temperature and oxidative stresses. Mutant RpoS protein expression was detected in the clinical isolate, and this RpoS was non-functional according to HPII activity and glycogen levels, which are positively regulated by RpoS and thus are used as indicators for RpoS function. A reporter assay with β-galactosidase indicated that the dysfunction occurred at the transcriptional level of genes regulated by RpoS. Furthermore, substitution analysis indicated that the hydrophobicity of the amino acid at residue 128 was critical for RpoS activity; the simulation analysis indicated that the amino acids of RNA polymerase (RNAP) that interact with RpoS residue 128 are hydrophobic, suggesting that this hydrophobic interaction is critical for RpoS activity. In addition, substitution of Ile128 to Pro128 abolished RpoS activity, possibly as a result of disruption of the secondsary structure around residue 128, indicating that the structure is also a crucial factor for RpoS activity. These results indicate that only one point mutation at a hydrophobic residue of the complex formed during transcription leads to a critical change in RpoS regulation. Moreover, we found that Ile128 is widely conserved among various bacteria: several bacterial strains have Met128 or Leu128, which are hydrophobic residues, and these strains had similar or higher RpoS activity than that observed with Ile128 in this study. These data indicate that the hydrophobicity of the amino acid at residue 128 is critical for RpoS activity and is consequently important for bacterial survival. Taken together, these findings may contribute to a deeper understanding of protein functional mechanisms and bacterial stress responses.

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Stress sigma factor RpoS degradation and translation are sensitive to the state of central metabolism.

Publications

Stress sigma factor RpoS degradation and translation are sensitive to the state of central metabolism.

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