Gould, Phillip S., Dyer, Nigel P., Croft, Wayne D., Ott, Sascha and Easton, A. J. (Andrew J.) (2014) Cellular mRNAs access second ORFs using a novel amino acid sequence-dependent coupled translation termination-reinitiation mechanism. RNA, 20 . pp. 373-381. doi:10.1261/rna.041574.113

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Abstract

Polycistronic transcripts are considered rare in the human genome. Initiation of translation of internal ORFs of eukaryotic genes has been shown to use either leaky scanning or highly structured IRES regions to access initiation codons. Studies on mammalian viruses identified a mechanism of coupled translation termination-reinitiation that allows translation of an additional ORF. Here, the ribosome terminating translation of ORF-1 translocates upstream to reinitiate translation of ORF-2. We have devised an algorithm to identify mRNAs in the human transcriptome in which the major ORF-1 overlaps a second ORF capable of encoding a product of at least 50 aa in length. This identified 4368 transcripts representing 2214 genes. We investigated 24 transcripts, 22 of which were shown to express a protein from ORF-2 highlighting that 3' UTRs contain protein-coding potential more frequently than previously suspected. Five transcripts accessed ORF-2 using a process of coupled translation termination-reinitiation. Analysis of one transcript, encoding the CASQ2 protein, showed that the mechanism by which the coupling process of the cellular mRNAs was achieved was novel. This process was not directed by the mRNA sequence but required an aspartate-rich repeat region at the carboxyl terminus of the terminating ORF-1 protein. Introduction of wobble mutations for the aspartate codon had no effect, whereas replacing aspartate for glutamate repeats eliminated translational coupling. This is the first description of a coordinated expression of two proteins from cellular mRNAs using a coupled translation termination-reinitiation process and is the first example of such a process being determined at the amino acid level.

Item Type:	Journal Article
Subjects:	Q Science > QH Natural history > QH301 Biology Q Science > QH Natural history > QH426 Genetics
Divisions:	Faculty of Science > Life Sciences (2010- ) Faculty of Science > Centre for Systems Biology
Library of Congress Subject Headings (LCSH):	Messenger RNA, Cytology -- Research, Amino acids
Journal or Publication Title:	RNA
Publisher:	Cold Spring Harbor Laboratory Press
ISSN:	1355-8382
Official Date:	10 January 2014
Dates:	Date Event 10 January 2014 Published
Date of first compliant deposit:	26 December 2015
Volume:	20
Page Range:	pp. 373-381
DOI:	10.1261/rna.041574.113
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access
Funder:	Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC), Research Councils UK (RCUK), University of Warwick, Engineering and Physical Sciences Research Council (EPSRC)
Grant number:	BB/I022880/1 (BBSRC)

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