title: Protein synthesis. Rqc2p and 60S ribosomal subunits mediate mRNA-independent elongation of nascent chains.
abstract: In Eukarya, stalled translation induces 40S dissociation and recruitment of the ribosome quality control complex (RQC) to the 60S subunit, which mediates nascent chain degradation. Here we report cryo-electron microscopy structures revealing that the RQC components Rqc2p (YPL009C/Tae2) and Ltn1p (YMR247C/Rkr1) bind to the 60S subunit at sites exposed after 40S dissociation, placing the Ltn1p RING (Really Interesting New Gene) domain near the exit channel and Rqc2p over the P-site transfer RNA (tRNA). We further demonstrate that Rqc2p recruits alanine- and threonine-charged tRNA to the A site and directs the elongation of nascent chains independently of mRNA or 40S subunits. Our work uncovers an unexpected mechanism of protein synthesis, in which a protein--not an mRNA--determines tRNA recruitment and the tagging of nascent chains with carboxy-terminal Ala and Thr extensions ("CAT tails").
authors.affiliation: Department of Biochemistry, University of Utah, UT 84112, USA.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Shen
authors.affiliation: Department of Biochemistry, Stanford University, Palo Alto, CA 94305, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Park
authors.affiliation: Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Yidan
authors.initials: Y
authors.lastname: Qin
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
authors.forename: Xueming
authors.initials: X
authors.lastname: Li
authors.affiliation: Mass Spectrometry and Proteomics Core Facility, University of Utah, UT 84112, USA.
authors.forename: Krishna
authors.initials: K
authors.lastname: Parsawar
authors.affiliation: Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA. Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA. California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, CA 94158, USA. Center for RNA Systems Biology, University of California, San Francisco, San Francisco, CA 94158, USA.
authors.forename: Matthew H
authors.initials: MH
authors.lastname: Larson
authors.affiliation: Department of Biochemistry, University of Utah, UT 84112, USA. Mass Spectrometry and Proteomics Core Facility, University of Utah, UT 84112, USA.
authors.forename: James
authors.initials: J
authors.lastname: Cox
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Alan M
authors.initials: AM
authors.lastname: Lambowitz
authors.affiliation: Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA. Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA. California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, CA 94158, USA. Center for RNA Systems Biology, University of California, San Francisco, San Francisco, CA 94158, USA. jonathan.weissman@ucsf.edu onn@stanford.edu adam.frost@ucsf.edu.
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Weissman
authors.affiliation: Department of Biochemistry, Stanford University, Palo Alto, CA 94305, USA. jonathan.weissman@ucsf.edu onn@stanford.edu adam.frost@ucsf.edu.
authors.forename: Onn
authors.initials: O
authors.lastname: Brandman
authors.affiliation: Department of Biochemistry, University of Utah, UT 84112, USA. Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA. jonathan.weissman@ucsf.edu onn@stanford.edu adam.frost@ucsf.edu.
authors.forename: Adam
authors.initials: A
authors.lastname: Frost
mesh_terms: D020285:Cryoelectron Microscopy; D009690:Nucleic Acid Conformation; D046908:Peptide Biosynthesis, Nucleic Acid-Independent; D011487:Protein Conformation; D012333:RNA, Messenger / Q000378:metabolism; D012344:RNA, Transfer, Ala / Q000737:chemistry / Q000378:metabolism; D012363:RNA, Transfer, Thr / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins; D054683:Ribosome Subunits, Large, Eukaryotic / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000648:ultrastructure; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D012333:RNA, Messenger; D012344:RNA, Transfer, Ala; D012363:RNA, Transfer, Thr; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; C577643:Tae2 protein, S cerevisiae; C552998:Ltn1 protein, S cerevisiae; C519403:Rkr1 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases