Talk on Saturday 09:00-09:15am submitted by Isobel Bowles
Identification of a tRNA-specific function for the tRNA methyltransferase Trm10 in Saccharomyces cerevisiae
Isobel Bowles (Ohio State Biochemistry Program), Aiswarya Krishnamohan, Abi Hubacher, Jane Jackman (Chemistry and Biochemistry, OSU)
tRNA methyltransferase 10 (Trm10) methylates N1 of guanosine at the 9th position of tRNA molecules using methyl donor S-adenosyl methionine (SAM). Upon deletion of trm10, Saccharomyces cerevisiae strains exhibit growth defects in the presence of antitumor drug 5-fluorouracil (5FU). We hypothesized that tRNA stability decreases with the lack of the m1G9 modification in trm10Δ strains and that certain tRNA species may be more reliant upon the methylated G9 nucleotide. We showed that when Trm10 substrate tRNATrp is overexpressed in trm10Δ strains, growth hypersensitivity to 5FU is rescued, while overexpression of 37 other tRNA species in S. cerevisiae does not rescue growth in the presence of the drug. We then demonstrated that levels of tRNATrp decrease in trm10Δ strains, and that these levels decrease further in the presence of 5FU, but another Trm10 substrate (tRNAGly) remains at a similar level in all conditions. These data indicate that the loss of m1G9 from tRNATrp is specifically responsible for the trm10Δ growth defect, even though Trm10 modifies 13 other tRNA substrates in S. cerevisiae. To identify the specific pathway associated with hypomodified tRNATrp quality control, pairwise deletion strains were created. These studies revealed that pairwise deletion of trm10 in combination with a known enzyme associated with multiple tRNA quality control pathways can rescue the 5FU-dependent growth defect. The effects of the m1G9 modification on tRNA structure and its interaction with Trm10 are also being determined with chemical footprinting methods, including SHAPE. Trm10 interactions with the tRNA at sites distant from the m1G9 modification were revealed that may play a role in the sensitivity of hypomodified tRNATrp. Together, these studies provide insight into the biological impact of loss of this highly conserved modification.
Keywords: tRNA modification, tRNA surveillance, SHAPE