Cycling of the Sm-like protein Hfq on the DsrA small regulatory RNA

被引:150
作者
Lease, RA [1 ]
Woodson, SA [1 ]
机构
[1] Johns Hopkins Univ, TC Jenkins Dept Biophys, Baltimore, MD 21218 USA
关键词
anti-sense RNA; RNA chaperone; non-coding RNA; RNA-protein interactions; riboregulation;
D O I
10.1016/j.jmb.2004.10.006
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Small RNAs (sRNAs) regulate bacterial genes involved in environmental adaptation. This RNA regulation requires Hfq, a bacterial Sm-like protein that stabilizes sRNAs and enhances RNA-RNA interactions. To understand the mechanism of target recognition by sRNAs, we investigated the interactions between Hfq, the sRNA DsrA, and its regulatory target rpoS mRNA, which encodes the stress response sigma factor. Nuclease footprinting revealed that Hfq recognized multiple sites in rpoS mRNA without significantly perturbing secondary structure in the 5' leader that inhibits translation initiation. Base-pairing with DsrA, however, made the rpoS ribosome binding site fully accessible, as predicted by genetic data. Hfq bound DsrA four times more tightly than the DsrA (.) rpoS RNA complex in gel mobility-shift assays. Consequently, Hfq is displaced rapidly from its high-affinity binding site on DsrA by conformational changes in DsrA, when DsrA base-pairs with rpoS mRNA. Hfq accelerated DsrA (.) rpoS RNA association and stabilized the RNA complex up to twofold. Hybridization of DsrA and rpoS mRNA was optimal when Hfq occupied its primary binding site on free DsrA, but was inhibited when Hfq associated with the DsrA (.) rpoS RNA complex. We conclude that recognition of rpoS mRNA is stimulated by binding of Hfq to free DsrA sRNA, followed by release of Hfq from the sRNA (.) mRNA complex. (C) 2004 Elsevier Ltd. All rights reserved.
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页码:1211 / 1223
页数:13
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