Nature Structural & Molecular Biology11, 1206 - 1214 (2004)
Published online: 7 November 2004; | doi:10.1038/nsmb858
Escherichia coli Hfq has distinct interaction surfaces for DsrA, rpoS and poly(A) RNAs
Peter J Mikulecky1, Meenakshi K Kaw2, Cristin C Brescia2, Jennifer C Takach1, Darren D Sledjeski2
& Andrew L Feig1
1
Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, Indiana
47405, USA.
2
Department of Microbiology and Immunology, Medical College of Ohio, Toledo, 3055 Arlington Avenue, Ohio
43614-5806, USA.
Correspondence should be addressed to Andrew L Feig afeig@indiana.edu
The bacterial Sm-like protein Hfq facilitates RNA-RNA interactions involved in post-transcriptional regulation of the stress response. Specifically, Hfq helps pair noncoding RNAs (ncRNAs) with complementary regions of target mRNAs. To probe the mechanism of this pairing, we generated a series of Hfq mutants and measured their affinity for RNAs like those with which Hfq must associate in vivo. We tested the mutants' DsrA-dependent activation of rpoS, and their ability to stabilize DsrA ncRNA against degradation in vivo. Our results suggest that Hfq has two independent RNA-binding surfaces. In addition to a well-known site around the core of the Hfq hexamer, we observe interactions with the distal face of Hfq, a new locus with which mRNAs and poly(A) sequences associate. Our model explains how Hfq can simultaneously bind a ncRNA and its mRNA target to facilitate the strand displacement reaction required for Hfq-dependent translational regulation.
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