FUNCTIONAL EVOLUTION OF PROMOTER-PROXIMAL PAUSING FACTORS IN THE REGULATION OF RNA POLYMERASE II TRANSCRIPTION
Booth, Gregory Thomas
Promoter-proximal pausing of RNA Polymerase II (Pol II) is now recognized as a ubiquitous mechanism for regulating gene expression in metazoans. By capturing engaged Pol II shortly after transcription initiation, genes are primed for activation of RNA synthesis, enabling cells to rapidly alter global transcription programs. However, despite conservation of many factors involved in establishing this regulatory platform, many eukaryotes do not control gene expression through this process. Here, the examination of the global transcriptional landscape in two distantly related yeast revealed unprecedented divergence in Pol II distributions across genes. Previously undescribed pause-like profiles were identified within promoter-proximal regions of the fission yeast, Schizosaccharomyces pombe, that are sensitive to loss of the conserved elongation factor, Spt4. Thus, fission yeast might employ a variant of the system of regulation found in higher eukaryotes In flies and mammals, Pol II arrested within the promoter proximal region of a gene can only be released through the activity of a positive-transcription elongation factor (P-TEFb), composed of kinase (Cdk9) and cyclin (CycT1/2) subunits. Investigating the functional impact of Cdk9 on transcription in fission yeast revealed that, unlike most metazoan systems, Pol II in S. pombe is capable of overcoming the early elongation barrier after kinase inhibition, although not without consequence. However, fission yeast lack the metazoan-specific negative elongation factor complex (NELF) involved in pausing, perhaps limiting their ability to control the release of Pol II through phosphorylation of the elongation complex. Ultimately, by depleting pausing factors from cell lines derived from Drosophila melanogaster, it was tested whether NELF is required for P-TEFb-regulated pause escape. While global transcription is largely unaffected by the loss of NELF, upon inhibition of Cdk9, a significant amount of Pol II is aberrantly released from the pause, suggesting reduced control of this regulation. These findings suggest that NELF may have evolutionarily refined an ancestral promoter-proximal architecture of the transcription elongation complex, giving rise to a novel mechanism for gene regulation.
Biochemistry; Molecular biology; Gene regulation; Genomics; Bioinformatics; Transcription; RNA Polymerase II
Lis, John T.
Lee, Siu Sylvia; Pleiss, Jeffrey A.
Biochemistry, Molecular and Cell Biology
Ph. D., Biochemistry, Molecular and Cell Biology
Doctor of Philosophy
Attribution 4.0 International
dissertation or thesis
Except where otherwise noted, this item's license is described as Attribution 4.0 International