The CGA codon decoding through tRNA^Arg (ICG) supply governed by Tad2/Tad3 in Saccharomyces cerevisiae

The CGA codon is a rare codon in Saccharomyces cerevisiae and is known to be inefficiently decoded by wobble pairing with Arg-tRNA(ICG). The tRNA^Arg (ICG) is post-transcriptionally edited from tRNA^Arg (ACG) by the anticodon first adenosine deamination enzyme Tad2/Tad3 complex. Experimental consecutive CGA codons cause ribosome stalling to result in the reduction of the encoding protein product. In this study, the additional supply of tRNA^Arg (ACG) genes that produce decoding Arg-tRNA(ICG) promoted the product level from the CGA12-luc reporter, revealing that the product reduction is essentially due to inefficient decoding and deficiency in the tRNA supply. The mature tRNA^Arg (ICG) and the precursor tRNA^Arg (ACG) ratios examined for cellular tRNA fraction revealed that the tRNA^Arg (ICG) ratio is maintained at less than 30% and is responsive to the Tad2/Tad3 expression level.