Rapid and robust signaling in the CsrA cascade via RNA-protein interactions and feedback regulation

Proc Natl Acad Sci U S A. 2013 Aug 6;110(32):13120-5. doi: 10.1073/pnas.1308476110. Epub 2013 Jul 22.

Abstract

Bacterial survival requires the rapid propagation of signals through gene networks during stress, but how this is achieved is not well understood. This study systematically characterizes the signaling dynamics of a cascade of RNA-protein interactions in the CsrA system, which regulates stress responses and biofilm formation in Escherichia coli. Noncoding RNAs are at the center of the CsrA system; target mRNAs are bound by CsrA proteins that inhibit their translation, CsrA proteins are sequestered by CsrB noncoding RNAs, and the degradation of CsrB RNAs is increased by CsrD proteins. Here, we show using in vivo experiments and quantitative modeling that the CsrA system integrates three strategies to achieve rapid and robust signaling. These strategies include: (i) the sequestration of stable proteins by noncoding RNAs, which rapidly inactivates protein activity; (ii) the degradation of stable noncoding RNAs, which enables their rapid removal; and (iii) a negative-feedback loop created by CsrA repression of CsrD production, which reduces the time for the system to achieve steady state. We also demonstrate that sequestration in the CsrA system results in signaling that is robust to growth rates because it does not rely on the slow dilution of molecules via cell division; therefore, signaling can occur even during growth arrest induced by starvation or antibiotic treatment.

Keywords: gene circuit; reverse engineering; synthetic biology; systems biology.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Algorithms
  • Biofilms / growth & development
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli / physiology
  • Escherichia coli Proteins / genetics*
  • Escherichia coli Proteins / metabolism
  • Feedback, Physiological
  • Gene Expression Regulation, Bacterial
  • Glucose-1-Phosphate Adenylyltransferase / genetics
  • Glucose-1-Phosphate Adenylyltransferase / metabolism
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Models, Genetic
  • Protein Binding
  • RNA, Bacterial / genetics*
  • RNA, Bacterial / metabolism
  • RNA, Long Noncoding / genetics
  • RNA, Long Noncoding / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA-Binding Proteins / genetics*
  • RNA-Binding Proteins / metabolism
  • Repressor Proteins / genetics*
  • Repressor Proteins / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / genetics*

Substances

  • CsrA protein, E coli
  • CsrB RNA, E coli
  • CsrD protein, E coli
  • Escherichia coli Proteins
  • Membrane Proteins
  • RNA, Bacterial
  • RNA, Long Noncoding
  • RNA, Messenger
  • RNA-Binding Proteins
  • Repressor Proteins
  • Green Fluorescent Proteins
  • Glucose-1-Phosphate Adenylyltransferase