Functional characterization of Ded1p, a DExD/H box RNA helicase, in saccharomyces cerevisiae
Abstract (Summary)The yeast DED1 protein (Ded1p) belongs to an evolutionarily conserved DExD/H-box protein family. Members of this family are involved in essentially all aspects of RNA metabolism, including pre-mRNA splicing, ribosomal biogenesis, RNA transport, and translation. They are often regarded as RNA helicases, or RNA unwindases, because some of them can couple ATP hydrolysis to unwinding short RNA duplexes in vitro. However, recent results suggest that, in vivo, DExD/H box proteins may dissociate specific RNA-binding proteins to remodel ribonucleoprotein complexes. Our lab previously found that Ded1p is a novel essential translation factor. However, Ded1p’s mechanistic role in translation remains to be defined.To examine Ded1p’s role further, I sought to identify its interacting proteins. In the first part of this dissertation (Chapter 1 to 4), I describe the unexpectedly finding that Ded1p binds to yeast L-A virus particles and accelerates the rate of L-A’s negative-strand RNA synthesis in vitro. Viruses are intracellular parasites that must use the host machinery to multiply, because their genomes are very small. Thus, identification of the host factors that perform essential functions in viral replication is of crucial importance to the understanding of virus-host interactions. The findings in this dissertation and the fact that Ded1p is also required for translating the brome mosaic virus RNA2 in yeast thus raise an intriguing possibility that Ded1p is one of the key host factors favored by several evolutionarily related RNA viruses including the human hepatitis C virus.In the second part of this dissertation (Chapter 5), I show that Ded1p is associated with active spliceosomes and inactivation of Ded1p affects spliceosome formation. Moreover, data from our lab demonstrates that introns accumulate in ded1 mutant strains after being shifted to non-permissive temperature. These findings indicate that Ded1p is also involved in pre-mRNA splicing. A growing body of evidence has suggested that many proteins can function in different nuclear processes in gene expression, implying a close inter-dependent relationship among these processes. The observations in this dissertation and the fact that Ded1p is a translation factor suggest a possible intimate coordination in gene expression between the nucleus and the cytoplasm.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:ded1p l a virus
Date of Publication:01/01/2004