A single sequence context cannot satisfy all non-AUG initiator codons in yeast†
- Equal contributors
1 Department of Life Science, National Central University, 300 Jung-da Rd., Jung-li 32001, Taiwan
2 Science Education Center, National Taiwan Normal University, 88 Ting-Chou Rd., Sec. 4, Taipei 11677, Taiwan
BMC Microbiology 2010, 10:188 doi:10.1186/1471-2180-10-188Published: 9 July 2010
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.
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.
This finding indicates that a sequence context that is favorable for a given non-ATG initiator codon might not be as favorable for another.