Affiliation:
1. Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
Abstract
ABSTRACT
Bacterial dual-function small RNAs regulate gene expression by RNA-RNA base pairing and also code for small proteins. SgrS is a dual-function small RNA in
Escherichia coli
and
Salmonella
that is expressed under stress conditions associated with accumulation of sugar-phosphates, and its activity is crucial for growth during stress. The base-pairing function of SgrS regulates a number of mRNA targets, resulting in reduced uptake and enhanced efflux of sugars. SgrS also encodes the SgrT protein, which reduces sugar uptake by a mechanism that is independent of base pairing. While SgrS base-pairing activity has been characterized in detail, little is known about how base pairing and translation of
sgrT
are coordinated. In the current study, we utilized a series of mutants to determine how translation of
sgrT
affected the efficiency of base pairing-dependent regulation and vice versa. Mutations that abrogated
sgrT
translation had minimal effects on base-pairing activity. Conversely, mutations that impaired base-pairing interactions resulted in increased SgrT production. Furthermore, while ectopic overexpression of
sgrS
mutant alleles lacking only one of the two functions rescued cell growth under stress conditions, the SgrS base-pairing function alone was indispensable for growth rescue when alleles were expressed from the native locus. Collectively, the results suggest that during stress, repression of sugar transporter synthesis via base pairing with sugar transporter mRNAs is the first priority of SgrS. Subsequently, SgrT is made and acts on preexisting transporters. The combined action of these two functions produces an effective stress response.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
39 articles.
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