Poster abstracts

Poster number 9 submitted by Nripesh Dhungel

Why is the yeast splicing endonuclease complex located in the cytoplasm and not in the nucleus?

Nripesh Dhungel (Molecular Genetics, The Ohio State University), Anita K. Hopper (Molecular Genetics, The Ohio State University)

Abstract:
Pre-tRNA splicing is a process that is critical to the viability of most eukaryotic cells. In vertebrates and yeast, the tRNA splicing endonuclease that cleaves the exon-intron junctions of pre-tRNA is composed of four proteins; Sen2p, Sen15p, Sen34p, and Sen54p. In yeast, splicing of pre-tRNAs occurs in the cytoplasm at the surface of the mitochondria (Yoshihisa et al., 2003), in contrast to mammalian pre-tRNA splicing, which occurs within the nucleus. The different location of pre-tRNA splicing machinery in yeast versus vertebrate cells raises the question of why this arrangement is maintained. My work aims to elucidate the spatial roles of the splicing endonuclease complex by directing the localization of the yeast pre-tRNA splicing machinery to the nucleus. To accomplish this, I have conjugated each protein of the splicing machinery to a nuclear localization signal and two GFP molecules. Thus far, we possess the constructs necessary to visualize different proteins of the splicing complex and we report nuclear localization of individual proteins of the machinery. Our next goal is to test that the proteins of the splicing machinery are retained in the nucleus and that they are in fact catalytically active. The ultimate goal will be to determine the physiological consequences of yeast with defective cytosolic splicing machinery and a functional complex in the nucleus.

References:
Yoshihisa T, Yunoki-Esaki K, Ohsima C, Tanaka N, Endo T.(2003). Possibility of cytoplasmic pre-tRNA splicing: the yeast tRNA splicing endonuclease mainly localizes on the mitochondria. Molecular Biology of the Cell 14,3266-3279.

Keywords: mitochondria, pre-tRNA, splicing endonuclease complex