Poster abstracts
Poster number 68 submitted by Tracy Roach
Mechanistic studies of substrate specificities exhibited by tRNA-His guanylyltransferase (Thg1)
Tracy M. Roach (OSBP), Krishna Patel (Department of Chemistry and Biochemistry, The Ohio State University), Jane Jackman (Department of Chemistry and Biochemistry, The Ohio State University)
Abstract:
tRNAHis guanylytransferase (Thg1) is responsible for adding a G-1 to tRNAHis across from an A73 discriminator nucleotide. This step is essential for histidyl tRNA synthetase to recognize and aminoacylate tRNAHis. Depletion of Thg1 in several different eukaryotes results in phenotypes, ranging from cell cycle defects to temperature sensitivity, which are not readily explained by the lack of mature tRNAHis. Therefore, we hypothesize that Thg1 may exhibit other functions beyond its role in tRNAHis metabolism. To understand these possible functions, it is important to establish the molecular basis for substrate recognition by Thg1 enzymes. To provide a uniform platform for comparing activities of different Thg1 family enzymes, Thg1 activity will be tested with a set of model RNAs. The substrates will be 5-18 base pair stem loops that mimic the coaxial stacking of the acceptor stem and T stem of tRNAHis. In order to provide a broad framework for understanding diverse enzyme recognition mechanisms, I will collectively and systematically characterize Thg1 family proteins from three eukaryotic organisms, S. cerevisiae, A. thaliana, and D. discoideum, for which distinct biochemical features of these enzymes have already been demonstrated. Among these enzymes, preferences for different substrates (tRNA vs. non-tRNA) and distinct gene structures have been observed, suggesting that these enzymes will exhibit distinct biochemical behavior with the tested RNAs that will help to provide insight into their biological role(s).
Keywords: 3-5 polymerization, RNA editing, tRNAHis guanylyltransferase