title: A novel mechanism for ribonuclease regulation: transfer-messenger RNA (tmRNA) and its associated protein SmpB regulate the stability of RNase R.
abstract: The amount of RNase R, an important degradative exoribonuclease, increases 3-10-fold under a variety of stress conditions. This elevation is due to posttranslational regulation in which the highly unstable RNase R protein becomes stabilized during stress. Here we identify two components of the trans-translation machinery, transfer-messenger RNA (tmRNA) and SmpB, that are responsible for the short half-life of RNase R in exponential phase cells. The absence of either lengthens the half-life of RNase R in vivo >6-fold. SmpB directly interacts with RNase R in vitro and is stimulated by tmRNA. The C-terminal region of RNase R, encompassing its basic region and adjacent S1 domain are required for the interaction; their removal eliminates binding and stabilizes RNase R in vivo. However, the binding of SmpB and tmRNA does not alter RNase R activity. These data define a previously unknown regulatory process in which the stability of an RNase is determined by its interaction with an RNA and an RNA-associated protein.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, 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: D015152:Blotting, Northern; D015153:Blotting, Western; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism*; D047468:Immunoprecipitation; D011485:Protein Binding; D055550:Protein Stability; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D016601:RNA-Binding Proteins; C430328:small protein B; C096222:tmRNA; D005095:Exoribonucleases; C080868:ribonuclease R