Poster abstracts

Poster number 125 submitted by William Swinehart

Dynamic modification of tRNA in the yeast S. cerevisiae

William Swinehart (The Department of Chemistry and Biochemistry), Jane Jackman (The Department of Chemistry and Biochemistry)

Abstract:
In recent years, there has been increasing 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. While roles for some modified nucleotides found near the tRNA anticodon in translation are relatively well-established, the biological function for modifications found in the remaining tRNA body is far less well-understood. Some modifications occurring in the tRNA core affect overall stability of the tRNA, and thus, loss of specific tRNA modifications in this region can lead to degradation via the rapid tRNA decay pathway. In addition, cells exposed to oxidative stress or growth arrest gain additional modifications on certain tRNAs. Thus modification of tRNA can be regulated in cells as a way to ensure overall quality and function of the tRNA pool, but the specific 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 allows Trm10 to modify non-cognate tRNAs in cells under stress, possibly preserving the structural integrity of the tRNA. We analyzed the modification status of the 5'-end of tRNAs exposed to two different stress conditions using primer extension. We show that when cells are either exposed to 5-fluourouracil or lack certain tRNA modification enzymes, additional primer extension stops corresponding to known tRNA modifications, including m¹G₉, are observed. These data support the hypothesis that the modification status of tRNAs is more dynamic than previously understood and opens the door to investigation of the physiological function of alternative tRNA modification patterns in cells.

Keywords: tRNA modification, Trm10, stress