tRNAomics: tRNA gene copy number variation and codon use provide bioinformatic evidence of a new anticodon:codon wobble pair in a eukaryote
- 1Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
- 2Commissioned Corps, US Public Health Service, Rockville, Maryland 20852, USA
Abstract
tRNA genes are interspersed throughout eukaryotic DNA, contributing to genome architecture and evolution in addition to translation of the transcriptome. Codon use correlates with tRNA gene copy number in noncomplex organisms including yeasts. Synonymous codons impact translation with various outcomes, dependent on relative tRNA abundances. Availability of whole-genome sequences allowed us to examine tRNA gene copy number variation (tgCNV) and codon use in four Schizosaccharomyces species and Saccharomyces cerevisiae. tRNA gene numbers vary from 171 to 322 in the four Schizosaccharomyces despite very high similarity in other features of their genomes. In addition, we performed whole-genome sequencing of several related laboratory strains of Schizosaccharomyces pombe and found tgCNV at a cluster of tRNA genes. We examined for the first time effects of wobble rules on correlation of tRNA gene number and codon use and showed improvement for S. cerevisiae and three of the Schizosaccharomyces species. In contrast, correlation in Schizosaccharomyces japonicus is poor due to markedly divergent tRNA gene content, and much worsened by the wobble rules. In japonicus, some tRNA iso-acceptor genes are absent and others are greatly reduced relative to the other yeasts, while genes for synonymous wobble iso-acceptors are amplified, indicating wobble use not apparent in any other eukaryote. We identified a subset of japonicus-specific wobbles that improves correlation of codon use and tRNA gene content in japonicus. We conclude that tgCNV is high among Schizo species and occurs in related laboratory strains of S. pombe (and expectedly other species), and tRNAome-codon analyses can provide insight into species-specific wobble decoding.
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↵3 Corresponding author
E-mail maraiar{at}mail.nih.gov
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Article published online ahead of print. Article and publication date are at http://www.rnajournal.org/cgi/doi/10.1261/rna.032151.111.
- Received December 23, 2011.
- Accepted April 5, 2012.
