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

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Bibliographic Details
Title:	Rqc2p and 60S ribosomal subunits mediate mRNA-independent elongation of nascent chains.
Authors:	Shen, Peter S., Park, Joseph, Yidan Qin, Xueming Li, Parsawar, Krishna, Larson, Matthew H., Cox, James, Yifan Cheng, Lambowitz, Alan M., Weissman, Jonathan S., Brandman, Onn, Frost, Adam
Source:	Science (pre-March 2025). 1/2/2015, Vol. 347 Issue 6217, p75-78. 4p.
Subjects:	Ribosomal RNA, Messenger RNA, Elongation factors (Biochemistry), Dissociation (Chemistry), Transfer RNA, Alanine, Threonine, Protein synthesis
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"). [ABSTRACT FROM AUTHOR]
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Database:	Psychology and Behavioral Sciences Collection

Description
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"). [ABSTRACT FROM AUTHOR]
ISSN:	00368075
DOI:	10.1126/science.1259724