Present address: Skaggs School of Pharmacy and Pharmaceutical Science, 9500 Gilman Drive, University of California-San Diego, La Jolla, CA 92093, USA.
Complex regulation of the global regulatory gene csrA: CsrA-mediated translational repression, transcription from five promoters by Eσ70 and EσS, and indirect transcriptional activation by CsrA
Article first published online: 23 JUN 2011
© 2011 Blackwell Publishing Ltd
Volume 81, Issue 3, pages 689–704, August 2011
How to Cite
Yakhnin, H., Yakhnin, A. V., Baker, C. S., Sineva, E., Berezin, I., Romeo, T. and Babitzke, P. (2011), Complex regulation of the global regulatory gene csrA: CsrA-mediated translational repression, transcription from five promoters by Eσ70 and EσS, and indirect transcriptional activation by CsrA. Molecular Microbiology, 81: 689–704. doi: 10.1111/j.1365-2958.2011.07723.x
- Issue published online: 24 JUL 2011
- Article first published online: 23 JUN 2011
- Accepted 27 May, 2011.
CsrA of Escherichia coli is an RNA-binding protein that globally regulates gene expression by repressing translation and/or altering the stability of target transcripts. Here we explored mechanisms that control csrA expression. Four CsrA binding sites were predicted upstream of the csrA initiation codon, one of which overlapped its Shine–Dalgarno sequence. Results from gel shift, footprint, toeprint and in vitro translation experiments indicate that CsrA binds to these four sites and represses its own translation by directly competing with 30S ribosomal subunit binding. Experiments were also performed to examine transcription of csrA. Primer extension, in vitro transcription and in vivo expression studies identified two σ70-dependent (P2 and P5) and two σS-dependent (P1 and P3) promoters that drive transcription of csrA. Additional primer extension studies identified a fifth csrA promoter (P4). Transcription from P3, which is indirectly activated by CsrA, is primarily responsible for increased csrA expression as cells transition from exponential to stationary-phase growth. Taken together, our results indicate that regulation of csrA expression occurs by a variety of mechanisms, including transcription from multiple promoters by two sigma factors, indirect activation of its own transcription, as well as direct repression of its own translation.