title: Hfq-bridged ternary complex is important for translation activation of rpoS by DsrA.
abstract: The rpoS mRNA, which encodes the master regulator σ(S) of general stress response, requires Hfq-facilitated base pairing with DsrA small RNA for efficient translation at low temperatures. It has recently been proposed that one mechanism underlying Hfq action is to bridge a transient ternary complex by simultaneously binding to rpoS and DsrA. However, no structural evidence of Hfq simultaneously bound to different RNAs has been reported. We detected simultaneous binding of Hfq to rpoS and DsrA fragments. Crystal structures of AU6A•Hfq•A7 and Hfq•A7 complexes were resolved using 1.8- and 1.9-Å resolution, respectively. Ternary complex has been further verified in solution by NMR. In vivo, activation of rpoS translation requires intact Hfq, which is capable of bridging rpoS and DsrA simultaneously into ternary complex. This ternary complex possibly corresponds to a meta-stable transition state in Hfq-facilitated small RNA-mRNA annealing process.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, P R China.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Wang
authors.forename: Lijun
authors.initials: L
authors.lastname: Wang
authors.forename: Jihui
authors.initials: J
authors.lastname: Wu
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Gong
authors.forename: Yunyu
authors.initials: Y
authors.lastname: Shi
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D035001:Host Factor 1 Protein / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D014176:Protein Biosynthesis; D012313:RNA / Q000737:chemistry*; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism; D058727:RNA, Small Untranslated / Q000737:chemistry / Q000378:metabolism*; D012808:Sigma Factor / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C405431:DsrA RNA, E coli; D029968:Escherichia coli Proteins; C087373:Hfq protein, E coli; D035001:Host Factor 1 Protein; D012333:RNA, Messenger; D058727:RNA, Small Untranslated; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D012313:RNA