title: Transfer-messenger RNA-SmpB protein regulates ribonuclease R turnover by promoting binding of HslUV and Lon proteases.
abstract: RNase R, an important exoribonuclease involved in degradation of structured RNA, is subject to a novel mechanism of regulation. The enzyme is extremely unstable in rapidly growing cells but becomes stabilized under conditions of stress, such as stationary phase or cold shock. RNase R instability results from acetylation which promotes binding of tmRNA-SmpB, two trans-translation factors, to its C-terminal region. Here, we examine how binding of tmRNA-SmpB leads to proteolysis of RNase R. We show that RNase R degradation is due to two proteases, HslUV and Lon. In their absence, RNase R is stable. We also show, using an in vitro system that accurately replicates the in vivo process, that tmRNA-SmpB is not essential, but it stimulates binding of the protease to the N-terminal region of RNase R and that it does so by a direct interaction between the protease and SmpB which stabilizes protease binding. Thus, a sequence of events, initiated by acetylation of a single Lys residue, results in proteolysis of RNase R in exponential phase cells. RNase R in stationary phase or in cold-shocked cells is not acetylated, and thereby remains stable. Such a regulatory mechanism, dependent on protein acetylation, has not been observed previously in bacterial cells.
authors.affiliation: Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, Florida 33101, USA.
authors.forename: Wenxing
authors.initials: W
authors.lastname: Liang
authors.forename: Murray P
authors.initials: MP
authors.lastname: Deutscher
mesh_terms: D000107:Acetylation; D049071:Endopeptidase Clp / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D005095:Exoribonucleases / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008239:Lysine / Q000737:chemistry; D008954:Models, Biological; D009841:Oligonucleotides / Q000235:genetics; D010447:Peptide Hydrolases / Q000737:chemistry; D049070:Protease La / Q000378:metabolism*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D059748:Proteolysis; D012313:RNA / Q000737:chemistry; D012329:RNA, Bacterial / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012260:Ribonucleases / Q000737:chemistry; D013997:Time Factors
chemical_list: C483566:ClpYQ protease, E coli; D029968:Escherichia coli Proteins; D009841:Oligonucleotides; D012329:RNA, Bacterial; D016601:RNA-Binding Proteins; C430328:small protein B; C096222:tmRNA; D012313:RNA; D005095:Exoribonucleases; D012260:Ribonucleases; C080868:ribonuclease R; D010447:Peptide Hydrolases; D049070:Protease La; D049071:Endopeptidase Clp; D008239:Lysine