A single sequence context cannot satisfy all non-AUG initiator codons in yeast.
BACKGROUND
Previous studies in Saccharomyces cerevisiae showed that ALA1 (encoding alanyl-tRNA synthetase) and GRS1 (encoding glycyl-tRNA synthetase) respectively use ACG and TTG as their alternative translation initiator codons. To explore if any other non-ATG triplets can act as initiator codons in yeast, ALA1 was used as a reporter for screening.


RESULTS
We show herein that except for AAG and AGG, all triplets that differ from ATG by a single nucleotide were able to serve as initiator codons in ALA1. Among these initiator codons, TTG, CTG, ACG, and ATT had ~50% initiating activities relative to that of ATG, while GTG, ATA, and ATC had ~20% initiating activities relative to that of ATG. Unexpectedly, these non-AUG initiator codons exhibited different preferences toward various sequence contexts. In particular, GTG was one of the most efficient non-ATG initiator codons, while ATA was essentially inactive in the context of GRS1.


CONCLUSIONS
This finding indicates that a sequence context that is favorable for a given non-ATG initiator codon might not be as favorable for another.
Chang
Chia-Pei
CP
Department of Life Science, National Central University, Jung-li, Taiwan.
Chen
Shun-Jia
SJ
Lin
Chen-Huan
CH
Wang
Tzu-Ling
TL
Wang
Chien-Chia
CC
D000412:Alanine-tRNA Ligase / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D018387:Codon, Initiator; D008969:Molecular Sequence Data; D010442:Peptide Chain Initiation, Translational; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
D018387:Codon, Initiator; D029701:Saccharomyces cerevisiae Proteins; D000412:Alanine-tRNA Ligase