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Journal of Bacteriology, November 2009, p. 6812-6821, Vol. 191, No. 22
0021-9193/09/$08.00+0     doi:10.1128/JB.00870-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

The Response Regulator SprE (RssB) Modulates Polyadenylation and mRNA Stability in Escherichia coli{triangledown}

Valerie J. Carabetta,1 Bijoy K. Mohanty,2 Sidney R. Kushner,2 and Thomas J. Silhavy1*

Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544,1 Department of Genetics, University of Georgia, Athens, Georgia 306052

Received 2 July 2009/ Accepted 8 September 2009

In Escherichia coli, the adaptor protein SprE (RssB) controls the stability of the alternate sigma factor RpoS ({sigma}38 and {sigma}S). When nutrients are abundant, SprE binds RpoS and delivers it to ClpXP for degradation, but when carbon sources are depleted, this process is inhibited. It also has been noted that overproduction of SprE is toxic. Here we show that null mutations in pcnB, encoding poly(A) polymerase I (PAP I), and in hfq, encoding the RNA chaperone Hfq, suppress this toxicity. Since PAP I, in conjunction with Hfq, is responsible for targeting RNAs, including mRNAs, for degradation by adding poly(A) tails onto their 3' ends, these data indicate that SprE helps modulate the polyadenylation pathway in E. coli. Indeed, in exponentially growing cells, sprE deletion mutants exhibit significantly reduced levels of polyadenylation and increased stability of specific mRNAs, similar to what is observed in a PAP I-deficient strain. In stationary phase, we show that SprE changes the intracellular localization of PAP I. Taken together, we propose that SprE plays a multifunctional role in controlling the transcriptome, regulating what is made via its effects on RpoS, and modulating what is degraded via its effects on polyadenylation and turnover of specific mRNAs.

* Corresponding author. Mailing address: Department of Molecular Biology, Princeton University, Princeton, NJ 08544. Phone: (609) 258-5899. Fax: (609) 258-2957. E-mail: tsilhavy{at}princeton.edu

{triangledown} Published ahead of print on 18 September 2009.

Journal of Bacteriology, November 2009, p. 6812-6821, Vol. 191, No. 22
0021-9193/09/$08.00+0     doi:10.1128/JB.00870-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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