Translational efficiency of a non-AUG initiation codon is significantly affected by its sequence context in yeast.
Previous studies have shown that translation of mrna for yeast glycyl-tRNA synthetase is alternatively initiated from UUG and a downstream AUG initiation codon. Evidence presented here shows that unlike an AUG initiation codon, efficiency of this non-AUG initiation codon is significantly affected by its sequence context, in particular the nucleotides at positions -3 to -1 relative to the initiation codon. A/A/R (R represents A Or G) and C/G/C appear to be the most and least favorable sequences at these positions, respectively. Mutation of the native context sequence -3 to -1 from AAA to CGC reduced translation initiation from the UUG codon up to 32-fold and resulted in loss of mitochondrial respiration. although an AUG initiation codon is, in general, unresponsive to context changes in yeast, an AAA (-3 to -1) to CGC mutation still reduced its initiating activity up to 8-fold under similar conditions. these results suggest that sequence context is more important for translation initiation in yeast than previously appreciated.
Department of Life Science, National Central University, Jung-li, Taiwan 32001.
Shun-Jia
SJ
Chen
Department of Life Science, National Central University, Jung-li, Taiwan 32001.
Grace
G
Lin
Department of Life Science, National Central University, Jung-li, Taiwan 32001.
Kuang-Jung
KJ
Chang
Department of Life Science, Tzu-Chi University, Hua-lien, Taiwan 97041.
Lu-Shu
LS
Yeh
Department of Life Science, National Central University, Jung-li, Taiwan 32001. Electronic address: dukewang@cc.ncu.edu.tw.
Chien-Chia
CC
Wang
D001483:Base Sequence; D003062:Codon; D018387:Codon, Initiator; D015966:Gene Expression Regulation, Fungal; D005816:Genetic Complementation Test; D008928:Mitochondria / Q000378:metabolism; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010442:Peptide Chain Initiation, Translational; D010957:Plasmids / Q000378:metabolism; D014176:Protein Biosynthesis; D012270:Ribosomes; D012441:Saccharomyces cerevisiae / Q000235:genetics*
D003062:Codon; D018387:Codon, Initiator