title: YmdB: a stress-responsive ribonuclease-binding regulator of E. coli RNase III activity.
abstract: The broad cellular actions of RNase III family enzymes include ribosomal RNA (rRNA) processing, mRNA decay, and the generation of noncoding microRNAs in both prokaryotes and eukaryotes. Here we report that YmdB, an evolutionarily conserved 18.8-kDa protein of Escherichia coli of previously unknown function, is a regulator of RNase III cleavages. We show that YmdB functions by interacting with a site in the RNase III catalytic region, that expression of YmdB is transcriptionally activated by both cold-shock stress and the entry of cells into stationary phase, and that this activation requires the sigma-factor-encoding gene, rpoS. We discovered that down-regulation of RNase III activity occurs during both stresses and is dependent on YmdB production during cold shock; in contrast, stationary-phase regulation was unperturbed in YmdB-null mutant bacteria, indicating the existence of additional, YmdB-independent, factors that dynamically regulate RNase III actions during normal cell growth. Our results reveal the previously unsuspected role of ribonuclease-binding proteins in the regulation of RNase III activity.
authors.affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, California 94305, USA.
authors.forename: Kwang-sun
authors.initials: KS
authors.lastname: Kim
authors.forename: Robert
authors.initials: R
authors.lastname: Manasherob
authors.forename: Stanley N
authors.initials: SN
authors.lastname: Cohen
mesh_terms: D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D003080:Cold Temperature; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D011485:Protein Binding; D043244:Ribonuclease III / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism*; D013312:Stress, Physiological / Q000502:physiology*; D013997:Time Factors
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C534806:YmdB protein, E coli; D012260:Ribonucleases; D043244:Ribonuclease III