title: Analysis of nonstop mRNA translation in the absence of tmRNA in Escherichia coli.
abstract: tmRNA, a product of ssrA gene, plays a crucial role in the quality control system that eliminates aberrant products of nonstop mRNAs in prokaryotes. Although tmRNA recycles ribosomes stalled at the 3' end of nonstop mRNAs, the fate of ribosomes that stall at the 3' end in the absence of tmRNA has not been extensively examined. Here we report our analysis of the translation status of nonstop mRNAs. Polysome analysis showed that nonstop mRNAs were translated efficiently, and peptidyl-tRNA was not found in any fraction in a DeltassrA strain. In vitro translation experiments using PURESYSTEM revealed that ribosomes translating nonstop mRNAs were dissociated from the 3' end of mRNA, and the peptidyl-tRNA was only weakly hydrolyzed in the monosome. These results suggest that the peptidyl-tRNA of a nonstop mRNA is hydrolyzed by an unknown factor(s) in vivo, thereby allowing a nonstop mRNA to be translated as efficiently as a normal mRNA. Possible factors involved in the hydrolysis of the peptidyl-tRNAs of nonstop mRNAs are discussed.
authors.affiliation: Department of Molecular Biology, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Kazushige
authors.initials: K
authors.lastname: Kuroha
authors.forename: Nobuo
authors.initials: N
authors.lastname: Horiguchi
authors.forename: Hiroji
authors.initials: H
authors.lastname: Aiba
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Inada
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; C019037:tRNA, peptidyl-; C096222:tmRNA