The MiaA tRNA modification enzyme is necessary for robust RpoS expression in Escherichia coli

J Bacteriol. 2014 Feb;196(4):754-61. doi: 10.1128/JB.01013-13. Epub 2013 Dec 2.

Abstract

The stationary phase/general stress response sigma factor RpoS (σ(S)) is necessary for adaptation and restoration of homeostasis in stationary phase. As a physiological consequence, its levels are tightly regulated at least at two levels. Multiple small regulatory RNA molecules modulate its translation, in a manner that is dependent on the RNA chaperone Hfq and the rpoS 5' untranslated region. ClpXP and the RssB adaptor protein degrade RpoS, unless it is protected by an anti-adaptor. We here find that, in addition to these posttranscriptional levels of regulation, tRNA modification also affects the steady-state levels of RpoS. We screened mutants of several RNA modification enzymes for an effect on RpoS expression and identified the miaA gene, encoding a tRNA isopentenyltransferase, as necessary for full expression of both an rpoS750-lacZ translational fusion and the RpoS protein. This effect is independent of rpoS, the regulatory RNAs, and RpoS degradation. RpoD steady-state levels were not significantly different in the absence of MiaA, suggesting that this is an RpoS-specific effect. The rpoS coding sequence is significantly enriched for leu codons that use MiaA-modified tRNAs, compared to rpoD and many other genes. Dependence on MiaA may therefore provide yet another way for RpoS levels to respond to growth conditions.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkyl and Aryl Transferases / genetics
  • Alkyl and Aryl Transferases / metabolism*
  • Bacterial Proteins / biosynthesis*
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli / growth & development
  • Gene Expression Regulation, Bacterial*
  • RNA, Transfer / metabolism*
  • Sigma Factor / biosynthesis*

Substances

  • Bacterial Proteins
  • Sigma Factor
  • sigma factor KatF protein, Bacteria
  • RNA, Transfer
  • Alkyl and Aryl Transferases
  • adenylate isopentenyltransferase