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

2015; American Association for the Advancement of Science; Volume: 347; Issue: 6217 Linguagem: Inglês

10.1126/science.1259724

1095-9203

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

RNA modifications and cancer

Tagging truncated proteins with CAT tails During the translation of a messenger RNA (mRNA) into protein, ribosomes can sometimes stall. Truncated proteins thus formed can be toxic to the cell and must be destroyed. Shen et al. show that the proteins Ltn1p and Rqc2p, subunits of the ribosome quality control complex, bind to the stalled and partially disassembled ribosome. Ltn1p, a ubiquitin ligase, binds near the nascent polypeptide exit tunnel on the ribosome, well placed to tag the truncated protein for destruction. The Rqc2p protein interacts with the transfer RNA binding sites on the partial ribosome and recruits alanine- and threonine-bearing tRNAs. Rqc2p then catalyzes the addition of these amino acids onto the unfinished protein, in the absence of both the fully assembled ribosome and mRNA. These so-called CAT tails may promote the heat shock response, which helps buffer against malformed proteins. Science , this issue p. 75