Protein synthesis. Rqc2p and 60S ribosomal subunits mediate mRNA-independent elongation of nascent chains

Peter S Shen; Joseph Park; Yidan Qin; Xueming Li; Krishna Parsawar; Matthew H Larson; James Cox; Yifan Cheng; Alan M Lambowitz; Jonathan S Weissman; Onn Brandman; Adam Frost

doi:10.1126/science.1259724

Protein synthesis. Rqc2p and 60S ribosomal subunits mediate mRNA-independent elongation of nascent chains

Science. 2015 Jan 2;347(6217):75-8. doi: 10.1126/science.1259724.

Authors

Peter S Shen¹, Joseph Park², Yidan Qin³, Xueming Li⁴, Krishna Parsawar⁵, Matthew H Larson⁶, James Cox⁷, Yifan Cheng⁴, Alan M Lambowitz³, Jonathan S Weissman⁸, Onn Brandman⁹, Adam Frost¹⁰

Affiliations

¹ Department of Biochemistry, University of Utah, UT 84112, USA.
² Department of Biochemistry, Stanford University, Palo Alto, CA 94305, USA.
³ 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.
⁴ Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
⁵ Mass Spectrometry and Proteomics Core Facility, University of Utah, UT 84112, USA.
⁶ 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.
⁷ Department of Biochemistry, University of Utah, UT 84112, USA. Mass Spectrometry and Proteomics Core Facility, University of Utah, UT 84112, USA.
⁸ 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.
⁹ Department of Biochemistry, Stanford University, Palo Alto, CA 94305, USA. jonathan.weissman@ucsf.edu onn@stanford.edu adam.frost@ucsf.edu.
¹⁰ 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.

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").

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Cryoelectron Microscopy
Nucleic Acid Conformation
Peptide Biosynthesis, Nucleic Acid-Independent*
Protein Conformation
RNA, Messenger / metabolism
RNA, Transfer, Ala / chemistry
RNA, Transfer, Ala / metabolism
RNA, Transfer, Thr / chemistry
RNA, Transfer, Thr / metabolism
RNA-Binding Proteins
Ribosome Subunits, Large, Eukaryotic / chemistry
Ribosome Subunits, Large, Eukaryotic / metabolism*
Ribosome Subunits, Large, Eukaryotic / ultrastructure
Saccharomyces cerevisiae / genetics
Saccharomyces cerevisiae / metabolism*
Saccharomyces cerevisiae Proteins / metabolism*
Saccharomyces cerevisiae Proteins / ultrastructure
Ubiquitin-Protein Ligases / metabolism*
Ubiquitin-Protein Ligases / ultrastructure

Substances

RNA, Messenger
RNA, Transfer, Ala
RNA, Transfer, Thr
RNA-Binding Proteins
Saccharomyces cerevisiae Proteins
Tae2 protein, S cerevisiae
Ltn1 protein, S cerevisiae
Rkr1 protein, S cerevisiae
Ubiquitin-Protein Ligases

Abstract

Publication types

MeSH terms

Substances

Grants and funding