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A broader role for the RNAPII phosphatase, FCP1, in transcription regulation

University of British Columbia

Transcription is the process by which DNA is copied into RNA in the cell. In eukaryotes, protein coding genes are transcribed by the enzyme RNA Polymerase II (RNAPII). RNAPII has a unique and highly conserved repeating heptad sequence at the C-terminus of its largest subunit, Rpb1, known as the C-terminal domain (CTD). The CTD is differentially phosphorylated throughout the transcriptional cycle, a property that is important for the dynamic recruitment of transcription-associated factors. The phosphorylation status of the CTD is maintained by several CTD-modifying enzymes. Two such CTD-modifying enzymes are the phosphatase, Fcp1, and the kinase, Cdk8. This thesis focuses on exploring the genetic interaction between FCP1 and CDK8. It expands the growing body of work that implicates Cdk8 as a stress response regulator, and identifies a role for Fcp1 in the stress response. Given that Fcp1 is essential, I probed the genes and pathways most sensitive to the truncation of fcp1, and uncovered an unexpected role for FCP1 and CDK8 in the regulation of Skn7 and the expression of Skn7-dependent oxidative stress response genes. Loss of CDK8 was able to overcome the transcriptional and posttranscriptional alterations caused by truncating fcp1 by increasing Skn7 stability, protein levels, and normalizing the expression of target genes. I also explored a role for FCP1 in Rpb1 biology. Truncation of fcp1 caused higher levels of Rpb1 protein that still associated with chromatin, despite not associating with Rpb3, another RNAPII subunit. It also resulted in higher levels of a lower molecular weight form of Rpb1. Additionally, this thesis expands the connection between FCP1 and CDK8 to include RPN4, a transcriptional activator of proteasome and stress response genes. Rpn4 has previously been shown to mediate the suppression of some CTD truncation phenotypes by loss of CDK8. Here, I found that the combined loss of RPN4 and CDK8 was able to normalize the increased levels of Rpb1 caused by the truncation of fcp1. Collectively, this thesis has expanded on our understanding of Fcp1 function in the cell and its role in transcription regulation.

Text

2022-02-28

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/77373

Medical Genetics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/