tRNA^His 5-methylcytidine levels increase in response to several growth arrest conditions in Saccharomyces cerevisiae

Abstract

tRNAs are highly modified, each with a unique set of modifications. Several reports suggest that tRNAs are hypomodified or, in some cases, hypermodified under different growth conditions and in certain cancers. We previously demonstrated that yeast strains depleted of tRNA His guanylyltransferase accumulate uncharged tRNA His lacking the G −1 residue and subsequently accumulate additional 5-methylcytidine (m 5 C) at residues C 48 and C 50 of tRNA His , due to the activity of the m 5 Cmethyltransferase Trm4. We show here that the increase in tRNA His m 5 C levels does not require loss of Thg1, loss of G −1 of tRNA His , or cell death but is associated with growth arrest following different stress conditions. We find substantially increased tRNA His m 5 C levels after temperature-sensitive strains are grown at nonpermissive temperature, and after wild-type strains are grown to stationary phase, starved for required amino acids, or treated with rapamycin. We observe more modest accumulations of m 5 C in tRNA His after starvation for glucose and after starvation for uracil. In virtually all cases examined, the additional m 5 C on tRNA His occurs while cells are fully viable, and the increase is neither due to the GCN4 pathway, nor to increased Trm4 levels. Moreover, the increased m 5 C appears specific to tRNA His , as tRNA Val(AAC) and tRNA Gly(GCC) have much reduced additional m 5 C during these growth arrest conditions, although they also have C 48 and C 50 and are capable of having increased m 5 C levels. Thus, tRNA His m 5 C levels are unusually responsive to yeast growth conditions, although the significance of this additional m 5 C remains unclear.

Conservation of an intricate circuit for crucial modifications of the tRNAPhe anticodon loop in eukaryotes

“…Thus, we found that m 7 G and m 2 G levels on tRNA Phe are decreased in S. pombe cells grown in EMM in the absence of thiamine (Table 2), similar to the changes in tRNA modification levels observed in S. cerevisiae cells grown under cellular stress conditions or in cells that have undergone growth arrest Chan et al 2012;Preston et al 2013). Furthermore, the finding that m 2 G levels of tRNA…”

Control of Saccharomyces cerevisiae pre-tRNA processing by environmental conditions

“…It has recently become appreciated that tRNA modifications that could alter the tRNA structure are affected by growth conditions. The effect of stress was reported for tRNA thiolation (Kamenski et al 2007;Damon et al 2015;Han et al 2015), m 5 C methylation (Preston et al 2013), and other modifications (Alings et al 2015). It is worth noting that activities of at least two enzymes responsible for end processing, RNase P and RNase Z, depend not on substrate sequence but proper structure (Takaku et al 2004;Mondragón 2013).…”

“…It has recently become appreciated that tRNA modifications are affected by stress (Chan et al 2010(Chan et al , 2012Preston et al 2013;Alings et al 2015;Damon et al 2015;Han et al 2015), but there are no reports regarding whether there is regulation of the activities responsible of pre-tRNA end-maturation. Here we investigated early steps of tRNA maturation for yeast grown at different temperatures (23°C-39°C) and in media with different carbon sources (glucose and glycerol).…”

Functional importance of Ψ38 and Ψ39 in distinct tRNAs, amplified for tRNAGln(UUG) by unexpected temperature sensitivity of the s2U modification in yeast

“…It thus seems possible that s 2 U formation of mitochondrial tRNA Lys(UUU) has components in common with the cytoplasmic s 2 U modification that are not shared by the other two mitochondrial tRNA species. Other examples of altered modifications during growth of yeast include increased m 5 C in the anticodon of tRNA Leu(CAA) and loss of m 2,2 G and Cm during oxidative stress (Chan et al 2010(Chan et al , 2012, and the increased m 5 C at C 48 and C 50 of tRNA His during the onset of stationary phase, amino acid starvation, and rapamycin treatment (Preston et al 2013). It thus seems plausible that these alterations in modifications are an integral part of a stress response.…”