Talk abstracts

Talk on Saturday 09:30-09:45am submitted by Nripesh Dhungel

Beyond tRNA cleavage: Novel essential function for yeast tRNA splicing endonuclease

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

Abstract:
Pre-tRNA splicing is an essential process in eukaryotic cells. In yeast, the tRNA splicing machinery is composed of three essential enzymes: the heterotetrameric tRNA splicing endonuclease (SEN complex), the tRNA ligase, and the 2'-phosphotransferase. While the SEN complex is conserved from yeast to vertebrates, the subcellular location where pre-tRNA splicing occurs is not conserved. In yeast, the SEN complex is located at the cytoplasmic surface of mitochondria and pre-tRNA splicing occurs in the cytoplasm whereas in vertebrates pre-tRNA splicing is nuclear. To understand why yeast pre-tRNA splicing occurs in the cytoplasm, we engineered yeast that express nuclear tRNA splicing machinery and investigated whether it can functionally substitute pre-tRNA splicing at mitochondria. We demonstrate that all three steps of pre-tRNA splicing and nuclear export of spliced tRNAs to the cytoplasm occur efficiently when endonucleolytic cleavage of introns occurs in the nucleus. However, pre-tRNA splicing in the nucleus fails to complement the growth defects of cells with defective mitochondrially-located SEN complex. The data support the hypothesis that the pre-tRNA splicing machinery in yeast surprisingly serves at least two essential functions, one of which is unrelated to pre-tRNA splicing and occurs in the cytoplasm/mitochondrial surface. Initial studies reveal that yeast tRNA splicing endonuclease subunits influence pre-ribosomal RNA processing.

Keywords: tRNA processing, rRNA processing, tRNA ligase