Characterization of the 3'-mRNA Decay Pathway in Yeast

University Of Texas At Austin, Austin TX

Investigators

Abstract

The proper spatial and temporal control of gene expression is essential for the normal growth and development of an organism. Gene expression is initiated by transcription but active degradation of mRNA is also necessary for strict temporal control. In eukaryotic cells there are two primary pathways for general mRNA degradation: a decapping-dependent pathway that utilizes 5'-exoribonucleases and a 3'-pathway that acts on mRNAs subsequent to deadenylation. Cell viability requires at least one of these pathways to be functional. In yeast, 5' decay is the major degradation pathway, but in mammalian cells evidence suggests that 3'-decay predominates. In addition to degrading mRNAs, the 3'-decay pathway blocks translation of poly(A) minus RNA that might arise as intermediates of degradation or from expression of viral messages such as the endogenous killer virus in yeast. The major components of this pathway are a heterotrimeric protein complex composed of Ski2p (a putative ATPase/RNA helicase), Ski3p and Ski8p, the Ski7 protein and a multisubunit exoribonuclease complex called the exosome. All components are required in vivo for 3'-decay. The Ski2/3/8 complex is thought to act as an adapter to facilitate mRNA 3'-degradation by the exosome. However, little is known about the molecular mechanism of 3'-decay and the interplay of the 3'-decay machinery with the translation apparatus. This project focuses on the biochemical function of the Ski2/3/8 complex and its interaction with Ski7p and the exosome in yeast.