Lack of tRNA Modification Isopentenyl-A37 Alters mRNA Decoding and Causes Metabolic Deficiencies in Fission Yeast

Abstract

tRNA isopentenyltransferases (Tit1) modify tRNA position 37, adjacent to the anticodon, to N⁶-isopentenyladenosine (i6A37) in all cells, yet the tRNA subsets selected for modification vary among species, and their relevance to phenotypes is unknown. We examined the function of i6A37 in Schizosaccharomyces pombe tit1⁺ and tit1-Δ cells by using a β-galactosidase codon-swap reporter whose catalytic activity is sensitive to accurate decoding of codon 503. i6A37 increased the activity of tRNA^Cys at a cognate codon and that of tRNA^Tyr at a near-cognate codon, suggesting that i6A37 promotes decoding activity generally and increases fidelity at cognate codons while decreasing fidelity at noncognate codons. S. pombe cells lacking tit1⁺ exhibit slow growth in glycerol or rapamycin. While existing data link wobble base U34 modifications to translation of functionally related mRNAs, whether this might extend to the anticodon-adjacent position 37 was unknown. Indeed, we found a biased presence of i6A37-cognate codons in high-abundance mRNAs for ribosome subunits and energy metabolism, congruent with the observed phenotypes and the idea that i6A37 promotes translational efficiency. Polysome profiles confirmed the decreased translational efficiency of mRNAs in tit1-Δ cells. Because subsets of i6A37-tRNAs differ among species, as do their cognate codon-sensitive mRNAs, these genomic variables may underlie associated phenotypic differences.

View correction statement:

Erratum for Lamichhane et al., Lack of tRNA Modification Isopentenyl-A37 Alters mRNA Decoding and Causes Metabolic Deficiencies in Fission Yeast

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00278-13.

ACKNOWLEDGMENTS

We thank Tom Dever for discussions and Marty Blum for media.

The Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, supports work in the Maraia lab. Work in the Begley lab is supported by the National Institutes of Health (grant 1R01ES017010).