Poster abstracts
Poster number 41 submitted by Ben Jepson
Understanding the biological significance of multiple zebrafish Trm10 homologs
Ben Jepson (MCDB)
Abstract:
The tRNA m1R9 methyltransferase (Trm10) family enzymes methylate the N-1 atom of purine residues at the ninth position of a subset of tRNAs. Trm10 enzymes are ubiquitous throughout Eukarya and Archaea, with eukaryotes encoding up to three homologs of Trm10. Humans, for example, encode the three homologs TRMT10A, TRMT10B and TRMT10C. Previously, we showed that human TRMT10A and TRMT10B have distinct, non-redundant biochemical activities. Human TRMT10A, like yeast Trm10, catalyzes m1G9 formation on multiple tRNA species whereas TRMT10B forms m1A9 specifically on tRNAAsp. To further probe the significance of these distinct enzyme activities and test their generality across multiple vertebrate models, we are using Danio rerio (zebrafish), which also encodes two cytosolic homologs, Trmt10a and Trmt10b. Like human TRMT10A, zebrafish Trmt10a rescues the trm10∆ phenotype in yeast and methylates yeast tRNAs in vivo. Conversely, neither zebrafish Trmt10b nor human TRMT10B are capable of rescuing the phenotype or methylating yeast substrates in vivo. Intriguingly, however, we discovered that human and zebrafish TRMT10B homologs differ significantly in their in vitro activities. In contrast to the human enzymes, zebrafish Trmt10a and Trmt10b do not show the same pattern of unique in vitro substrate specificities, although they do modify some tRNAs with different catalytic rates. These studies reveal that determinants of substrate specificity of individual Trm10 homologs are complex, and often can not be fully recapitulated by in vitro analysis. In order to fully elucidate the biological functions of these enzymes, we are using mutant zebrafish lines to analyze the specific roles of each enzyme in tRNA modification in vivo.
Keywords: tRNA modification, Trm10, m1R9