title: SsrA-mediated tagging and proteolysis of LacI and its role in the regulation of lac operon.
abstract: SsrA RNA of Escherichia coli, also known as 10Sa RNA or tmRNA, acts both as tRNA and mRNA when ribosomes are paused at the 3' end of an mRNA lacking a stop codon. This process, referred to as trans-translation, leads to the addition of a short peptide tag to the C-terminus of the incomplete nascent polypeptide. The tagged polypeptide is then degraded by C-terminal-specific proteases. Here, we focused on endogenous targets for the SsrA system and on a potential regulatory role of SsrA RNA. First, we show that trans-translation events occur frequently in normally growing E. COLI: cells. More specifically, we report that the lacI mRNA encoding Lac repressor (LacI) is a specific natural target for trans-translation. The binding of LacI to the lac operators results in truncated lacI mRNAs that are, in turn, recognized by the SsrA system. The SsrA-mediated tagging and proteolysis of LacI appears to play a role in cellular adaptation to lactose availability by supporting a rapid induction of lac operon expression.
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Abo
authors.forename: T
authors.initials: T
authors.lastname: Inada
authors.forename: K
authors.initials: K
authors.lastname: Ogawa
authors.forename: H
authors.initials: H
authors.lastname: Aiba
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D007544:Isopropyl Thiogalactoside / Q000494:pharmacology; D007763:Lac Operon / Q000235:genetics*; D056968:Lac Repressors; D008969:Molecular Sequence Data; D009154:Mutation; D009875:Operator Regions, Genetic / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D014176:Protein Biosynthesis / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein; D029968:Escherichia coli Proteins; D056968:Lac Repressors; C539064:LacI protein, E coli; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012097:Repressor Proteins; C096222:tmRNA; D007544:Isopropyl Thiogalactoside; D012343:RNA, Transfer