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Ribosome rescue by Escherichia coli ArfA (YhdL) in the absence of trans ‐translation system
Author(s) -
Chadani Yuhei,
Ono Katsuhiko,
Ozawa Shinichiro,
Takahashi Yuichiro,
Takai Kazuyuki,
Nanamiya Hideaki,
Tozawa Yuzuru,
Kutsukake Kazuhiro,
Abo Tatsuhiko
Publication year - 2010
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07375.x
Subject(s) - ribosome , biology , translation (biology) , puromycin , microbiology and biotechnology , transfer rna , messenger rna , protein biosynthesis , release factor , stop codon , rna , start codon , genetics , gene
Summary Although SsrA(tmRNA)‐mediated trans ‐translation is thought to maintain the translation capacity of bacterial cells by rescuing ribosomes stalled on messenger RNA lacking an in‐frame stop codon, single disruption of ssrA does not crucially hamper growth of Escherichia coli . Here, we identified YhdL (renamed ArfA for a lternative r ibosome‐rescue f actor) as a factor essential for the viability of E. coli in the absence of SsrA. The ssrA–arfA synthetic lethality was alleviated by SsrA DD , an SsrA variant that adds a proteolysis‐refractory tag through trans ‐translation, indicating that ArfA‐deficient cells require continued translation, rather than subsequent proteolysis of the truncated polypeptide. In accordance with this notion, depletion of SsrA in the Δ arfA background led to reduced translation of a model protein without affecting transcription, and puromycin, a codon‐independent mimic of aminoacyl‐tRNA, rescued the bacterial growth under such conditions. That ArfA takes over the role of SsrA was suggested by the observation that its overexpression enabled detection of the polypeptide encoded by a model non‐stop mRNA, which was otherwise SsrA‐tagged and degraded. In vitro , purified ArfA acted on a ribosome‐nascent chain complex to resolve the peptidyl‐tRNA. These results indicate that ArfA rescues the ribosome stalled at the 3′ end of a non‐stop mRNA without involving trans ‐translation.