The genetic information transfer pathway, which includes transcription, precursor messenger RNA (pre-mRNA) processing, mRNA export, translation, and mRNA turnover, is a highly integrated process in higher eukaryotes. This integration is mainly achieved by the C-terminal domain (CTD) of the largest subunit of the RNA polymerase II (Pol II), which serves as a platform for recruiting RNA processing factors. In yeast Saccharomyces cerevisiae, however, support for the coupling of transcription and splicing is far less assuring. Here we show, via our studies of Sub2p, a DExD/H-box protein essential for both splicing and mRNA export, that transcription and splicing are functionally coupled in yeast. The DExD/H-box proteins are often referred to as RNA helicases, but are increasingly viewed as ribonucleoprotein ATPases (RNPases) that can remodel specific RNPs in vivo. We first show that specific alterations of the intron branch-site binding protein (BBP) can eliminate the requirement for Sub2p, thus illuminating a principal role for Sub2p to remove BBP and Mud2p from the branch-site region. Unexpectedly, we uncovered a panoply of genetic and chemical perturbations of the yeast transcription machinery that can also bypass Sub2p’s requirement. Chromatin-immunoprecipitation (ChIP) analysis revealed that these perturbations significantly reduce the effectiveness of co-transcriptional recruitment of BBP, thereby alleviating the lethal outcome of losing Sub2p. These findings also suggest a potential selective advantage for yeast to exploit modifications in a kinetically coupled upstream pathway to offset the catastrophic loss of key components in the downstream pathways.
|Commitee:||Gopalan, Venkat, Herman, Paul, Simcox, Amanda|
|School:||The Ohio State University|
|Department:||Molecular, Cellular, and Developmental Biology|
|School Location:||United States -- Ohio|
|Source:||DAI-B 79/09(E), Dissertation Abstracts International|
|Keywords:||Bbp, Coupling, Rna helicase, Rnpase, Sub2, Transcription|
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