A Molecular Genetic Analysis of Transcription Termination in Yeast

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Hyman The long term objective of the project is to understand the mechanism of transcription teruiination in eukaryotes. It is well documented that cleavage of pre-mRNA is coupled to transcription termination. However, many aspects of the termination reaction remain ill-defined, in particular, the mechanism of nascent transcript release and the identification of novel factors that participate in 3' end formation. Thus, the objective of this research is to examine mechanism(s) by which RNA processing and transcription termination coordinate formation of a functional mRNA 3' end. The yeast model system was employed to take advantage of combined molecular genetic and biochemical approaches. GRS1, a putative glycyl tRNA synthetase, was identified in a screen for genes involved in 3' end formation. Strains carrying a grsi1-1 mutation cleave and polyadenylate pre-mRNAs in vitro at wild type levels but exhibit increased readthrough transcription of a polyadenylation signal. Thus, the hypothesis is that Grslp promotes efficient transcription termination. To test this, experiments are underway to: a. examine the role of Grs1p in the termination reaction; b. carry out structure/function studies of Grs1p to determine if the same domains responsible for 3' end formation are important for tRNA acylation. The mechanism by which genes are regulated and expressed is complex. This area is under intense investigation as gene transcription is critical for human biology and disease mechanisms. A component of the transcription reaction that is not well understood deals with how the enzyme that synthesizes the RNA from the DNA template ends the reaction. This research describes the novel finding that a component of the termination reaction is also involved in other cellular functions. This is important as it provides a connection between two fundamental processes in cells, the synthesis of RNA and the synthesis of proteins. Thus, the significance of the research is to provide insight into how cells express individual genes and how this process is related to other cellular functions