title: Growth Phase-dependent Variation of RNase BN/Z Affects Small RNAs: REGULATION OF 6S RNA.
abstract: RNase BN, the RNase Z family member in E. coli, can participate in the processing of tRNA precursors. However, this function only becomes apparent when other processing enzymes are absent, raising the question of its primary physiological role. Here, we show that RNase BN itself is subject to growth phase-dependent regulation, because both rbn mRNA and RNase BN protein are at their highest levels in early exponential phase, but then decrease dramatically and are essentially absent in stationary phase. As a consequence of this variation, certain small RNAs, such as 6S RNA, remain low in exponential phase cells, and increase greatly in stationary phase. RNase BN affects 6S RNA abundance by decreasing its stability in exponential phase. RNase BN levels increase rapidly as cells exit stationary phase and are primarily responsible for the decrease in 6S RNA that accompanies this process. Purified RNase BN directly cleaves 6S RNA as shown by in vitro assays, and the 6S RNA:pRNA duplex is an even more favorable substrate of RNase BN. The exoribonuclease activity of RNase BN is unnecessary because all its action on 6S RNA is due to endonucleolytic cleavages. These data indicate that RNase BN plays an important role in determining levels of the global transcription regulator, 6S RNA, throughout the growth cycle.
authors.affiliation: From the Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, Florida 33101.
authors.forename: Hua
authors.initials: H
authors.lastname: Chen
authors.affiliation: From the Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, Florida 33101.
authors.forename: Tanmay
authors.initials: T
authors.lastname: Dutta
authors.affiliation: From the Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, Florida 33101 m.deutscher@med.miami.edu.
authors.forename: Murray P
authors.initials: MP
authors.lastname: Deutscher
mesh_terms: D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism*; D048168:Escherichia coli K12 / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism*; D020871:RNA Stability / Q000502:physiology*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism*
chemical_list: C411065:6S RNA; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D022661:RNA, Untranslated; D004722:Endoribonucleases; D005095:Exoribonucleases; C110250:RNase Z; C038206:ribonuclease BN
keywords: Escherichia coli (E. coli); RNA metabolism; RNA turnover; bacteria; ribonuclease; small RNA