Regulation Of Transcription By RNA Polymerase II In <i>S. pombe</i>

An understanding of the mechanisms underlying the various stages of transcription is crucial to find solutions to the problems caused by mis-expression of genes that may give rise to a host of human diseases. My thesis research focusses on an analysis of the RNA Polymerase II elongation factor Ell1/Eaf1 in S. pombe. Eleven-nineteen lysine-rich in leukemia (ELL) is encoded by a gene involved in translocations with MLL in leukemia and forms a tight complex with ELL-associated factors (EAF). ELL/EAF is an RNA polymerase II elongation factor that in metazoa can assemble into a larger assembly that also includes P-TEFb and other proteins encoded by genes involved in MLL translocations. This larger assembly, sometimes called SEC, binds to a specific "docking site" in the metazoan Mediator complex. Distantly related ELL- and EAF-like genes were identified in S. pombe that encode Ell1/Eaf1 and can stimulate Pol II elongation in vitro. My thesis addresses two distinct projects, with overlapping motivations: First, to see whether S. pombe might provide a good model for functional studies of the Mediator and ELL/EAF interaction, I carried out a thorough proteomic analysis of S. pombe Mediator and defined several new subunits. My results were recently published as part of a collaborative structural analysis of S. pombe Mediator. Second, I used a combination of biochemical, genetic, and genomic approaches to characterize Ell1/Eaf1 function in fission yeast. Using mass spectrometry, I identified an uncharacterized sequence orphan, SPAC6G9.15c, that associates with both Ell1 and Eaf1 to form a ternary complex that, based on ChIP-seq localizes at genes with high RNA Pol II occupancy. I also performed an SGA screen for genes that genetically interact with ell1, eaf1, and SPAC6G9.15c and identified a set of overlapping genes that interact with all three, as well as others that interact only with ell1