title: Reduced action of polypeptide release factors induces mRNA cleavage and tmRNA tagging at stop codons in Escherichia coli.
abstract: Certain C-terminal sequences of nascent peptide cause an efficient protein tagging by tmRNA system at stop codons in Escherichia coli. Here, we demonstrate that both mRNA cleavage and tmRNA tagging occur at UAG stop codon recognized specifically by polypeptide release factor 1 (RF-1) when the activity of RF-1 is reduced by a mutation in the prfA gene without requirement of particular C-terminal sequences of nascent peptide. The tmRNA tagging and mRNA cleavage in the prfA mutant were eliminated when the wild-type RF-1 but not RF-2 was supplied from plasmid. In addition, depletion of either RF-1 or RF-2 induces endonucleolytic cleavage and tmRNA tagging at UAG or UGA stop codons respectively. We conclude that ribosome stalling at the cognate stop codon caused by reduced activity or expression of RF-1 or RF-2 is responsible for mRNA cleavage. The present data along with our previous studies strongly suggest that ribosome stalling leads to endonucleolytic cleavage of mRNA in general resulting in non-stop mRNA and that the 3' end of non-stop mRNA is probably only target for the tmRNA system.
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.forename: Teruaki
authors.initials: T
authors.lastname: Yokota
authors.forename: Koichi
authors.initials: K
authors.lastname: Ito
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Hiroji
authors.initials: H
authors.lastname: Aiba
mesh_terms: D018388:Codon, Terminator; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D010454:Peptide Termination Factors / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D014157:Transcription Factors
chemical_list: D018388:Codon, Terminator; D029968:Escherichia coli Proteins; D010454:Peptide Termination Factors; D010455:Peptides; D012329:RNA, Bacterial; D012333:RNA, Messenger; D014157:Transcription Factors; C096222:tmRNA