摘要
Upon initiation at a start codon,the ribosome must maintain the correct reading frame for hundreds of codons in order to produce functional proteins.While some sequence elements are able to trigger programmed ribosomal frameshifing(PRF),very little is known about how the ribosome normally prevents spontaneous frameshif errors that can have dire consequences if uncorrected.Using high resolution ribosome profling data sets,we discovered that the translating ribosome uses the 3�end of 18S rRNA to scan the AUG-like codons afer the decoding process.Te postdecoding mRNA:rRNA interaction not only contributes to predominant translational pausing,but also provides a retrospective mechanism to safeguard the ribosome in the correct reading frame.Partially eliminating the AUG-like“sticky”codons in the reporter message leads to increased+1 frameshif errors.Remarkably,mutating the highly conserved CAU triplet of 18S rRNA globally changes the codon“stickiness”.Further supporting the role of“sticky”sequences in reading frame maintenance,the codon composition of open reading frames is highly optimized across eukaryotic genomes.Tese results suggest an important layer of information embedded within the protein-coding sequences that instructs the ribosome to ensure reading frame fdelity during translation.
基金
We would like to thank Qian lab members for helpful discussion.We also thank Drs.Sunnie Tompson(University of Alabama)for providing us with the CrPV reporter construct and Vincent Mauro(Te Scripps Research Institute)for sending us constructs expressing 18S rRNA.We thank Cornell University Life Sciences Core Laboratory Center for performing deep sequencing.Tis work was supported by grants to Shu-Bing Qian from National Institutes of Health(R01AG042400)
DOD Idea Award(W81XWH-14-1-0068),and HHMI Faculty Scholar(55108556).
