SsrA-mediated tagging and proteolysis of LacI and its role in the regulation of lac operon.
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.
Abo
T
T
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.
Inada
T
T
Ogawa
K
K
Aiba
H
H
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
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