Talk abstracts

Talk on Wednesday 04:30-04:45pm submitted by William Swinehart

Dynamic tRNA modification in the yeast Saccharomyces cerevisiae

William Swinehart (Dept of Chemistry and Biochemistry, The Ohio State University), Jane E. Jackman (Dept of Chemistry and Biochemistry, The Ohio State University)

Abstract:
Interest in the function of numerous post-transcriptional modifications of tRNA bases and sugars that are known to occur in all three domains of life has increased in recent years. While translation-related roles for some modified nucleotides found near the tRNA anticodon are relatively well-established, the biological function of many modifications found in the remaining tRNA body is far less well-understood. Some modifications occurring in the core of the tRNA affect overall stability, and thus, loss of specific modifications may lead to degradation. In addition, cells exposed to oxidative stress or growth arrest may gain additional modifications on certain tRNAs. These data suggest that tRNA modification can be regulated in cells as a way to ensure overall quality and function of the tRNA pool, but the consequences of alternative tRNA modification patterns remain to be fully investigated.

In this work, we show that the yeast m¹G₉ methyltransferase, Trm10, displays the ability to modify additional tRNA substrates, both in vitro and in vivo, beyond the set of tRNA species that are normally modified in wild-type S. cerevisiae. We hypothesize that this expanded mode of substrate specificity is advantageous in that it could allow Trm10 to modify non-cognate tRNAs in cells under stress, possibly preserving the structural integrity of the tRNA. Using in vitro activity assays with tRNA chimera, we have identified tRNA elements that affect substrate specificity of yeast Trm10. Moreover, analysis of the modification status of the 5'-end of tRNAs exposed to two different stress conditions using primer extension revealed additional primer extension stops corresponding to positions of known tRNA modifications, including N-1 methylation at G₉. These data support the hypothesis that the modification status of tRNAs is much more dynamic than previously understood and opens the door to further investigation of the physiological function of alternative tRNA modification patterns in cells.

Keywords: tRNA modification, tRNA structure, specificity