Translation initiation factor eIF3 promotes programmed stop codon readthrough.
Programmed stop codon readthrough is a post-transcription regulatory mechanism specifically increasing proteome diversity by creating a pool of C-terminally extended proteins. During this process, the stop codon is decoded as a sense codon by a near-cognate tRNA, which programs the ribosome to continue elongation. The efficiency of competition for the stop codon between release factors (eRFs) and near-cognate tRNAs is largely dependent on its nucleotide context; however, the molecular mechanism underlying this process is unknown. Here, we show that it is the translation initiation (not termination) factor, namely eIF3, which critically promotes programmed readthrough on all three stop codons. In order to do so, eIF3 must associate with pre-termination complexes where it interferes with the eRF1 decoding of the third/wobble position of the stop codon set in the unfavorable termination context, thus allowing incorporation of near-cognate tRNAs with a mismatch at the same position. We clearly demonstrate that efficient readthrough is enabled by near-cognate tRNAs with a mismatch only at the third/wobble position. Importantly, the eIF3 role in programmed readthrough is conserved between yeast and humans.
Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic Faculty of Science, Charles University, Vinicna 5, Prague 128 44, the Czech Republic.
Petra
P
Beznosková
Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic.
Susan
S
Wagner
Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic.
Myrte Esmeralda
ME
Jansen
School of Biosciences, University of Kent, Kent CT2 7NJ, UK.
Tobias
T
von der Haar
Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic valasekl@biomed.cas.cz.
Leoš Shivaya
LS
Valášek
D018388:Codon, Terminator; D039621:Eukaryotic Initiation Factor-3 / Q000378:metabolism*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D010303:Paromomycin / Q000494:pharmacology; D010441:Peptide Chain Elongation, Translational; D010442:Peptide Chain Initiation, Translational; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism; D015003:Yeasts / Q000235:genetics
D018388:Codon, Terminator; D039621:Eukaryotic Initiation Factor-3; D012346:RNA, Transfer, Amino Acyl; D010303:Paromomycin