title: Release factor eRF3 mediates premature translation termination on polylysine-stalled ribosomes in Saccharomyces cerevisiae.
abstract: Ribosome stalling is an important incident enabling the cellular quality control machinery to detect aberrant mRNA. Saccharomyces cerevisiae Hbs1-Dom34 and Ski7 are homologs of the canonical release factor eRF3-eRF1, which recognize stalled ribosomes, promote ribosome release, and induce the decay of aberrant mRNA. Polyadenylated nonstop mRNA encodes aberrant proteins containing C-terminal polylysine segments which cause ribosome stalling due to electrostatic interaction with the ribosomal exit tunnel. Here we describe a novel mechanism, termed premature translation termination, which releases C-terminally truncated translation products from ribosomes stalled on polylysine segments. Premature termination during polylysine synthesis was abolished when ribosome stalling was prevented due to the absence of the ribosomal protein Asc1. In contrast, premature termination was enhanced, when the general rate of translation elongation was lowered. The unconventional termination event was independent of Hbs1-Dom34 and Ski7, but it was dependent on eRF3. Moreover, premature termination during polylysine synthesis was strongly increased in the absence of the ribosome-bound chaperones ribosome-associated complex (RAC) and Ssb (Ssb1 and Ssb2). On the basis of the data, we suggest a model in which eRF3-eRF1 can catalyze the release of nascent polypeptides even though the ribosomal A-site contains a sense codon when the rate of translation is abnormally low.
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, Freiburg, Germany Center for Biological Signaling Studies (BIOSS), University of Freiburg, Freiburg, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Chiabudini
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, Freiburg, Germany.
authors.forename: Arlette
authors.initials: A
authors.lastname: Tais
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, Freiburg, Germany.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, Freiburg, Germany.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Hayashi
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, Freiburg, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Wölfle
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, Freiburg, Germany.
authors.forename: Edith
authors.initials: E
authors.lastname: Fitzke
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, Freiburg, Germany Center for Biological Signaling Studies (BIOSS), University of Freiburg, Freiburg, Germany sabine.rospert@biochemie.uni-freiburg.de.
authors.forename: Sabine
authors.initials: S
authors.lastname: Rospert
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D018388:Codon, Terminator; D019204:GTP-Binding Proteins / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D010454:Peptide Termination Factors / Q000235:genetics / Q000378:metabolism; D011107:Polylysine / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C111825:ASC1 protein, S cerevisiae; D048868:Adaptor Proteins, Signal Transducing; D018388:Codon, Terminator; D018840:HSP70 Heat-Shock Proteins; D010454:Peptide Termination Factors; C095192:SSB1 protein, S cerevisiae; C068068:SUP35 protein, S cerevisiae; C080775:SUP45 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C087971:peptide-chain-release factor 3; D011107:Polylysine; D000251:Adenosine Triphosphatases; D019204:GTP-Binding Proteins; C494470:SSB2 protein, S cerevisiae