The control of RNA Polymerase elongation and termination is not fully understood. In this work, we will investigate the role of the C-terminal domain phosphatases Rtr1 and Ssu72 in the regulation of RNA Polymerase II (RNAPII) elongation and termination. Our preliminary findings suggest that deletion of Rtr1 results in global changes in the efficiency of early termination of RNAPII during transcription elongation. Previous work has shown that disruption of Ssu72 function leads to decreased RNAPII termination resulting in terminator read-through defects. In this proposal, we will test how perturbations of each phosphatase effect transcription elongation and termination. Additionally, we will perform enzymatic characterization of Rtr1 and Ssu72 substrate specificity to further characterize their mechanisms of action. Finally, we will determine the degree of interplay between Rtr1 and Ssu72 to determine if they are able to target unique and/or overlapping sites within the RNAPII C-termination domain. Overall, these studies will shed light on the fundamental process of RNAPII transcription control which is disrupted in numerous disease states in humans.
The phosphorylation status of the RNA Polymerase II C-terminal domain impacts the recruitment of numerous proteins during transcription that carry out processing of the nascent RNA as well as regulation of chromatin modification and organization. This work will define the mechanisms through which the CTD phosphatase Rtr1 and Ssu72 coordinate these processes through the removal of serine 5 phosphorylation on RNAPII. This work will reveal how CTD phosphorylation regulates the processes of pervasive transcription, RNAPII elongation, and termination which are all fundamental processes that control the fitness of eukaryotic cells.