Access Type

Open Access Dissertation

Date of Award

January 2012

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Biological Sciences

First Advisor

Athar Ansari

Abstract

My Ph.D. dissertation work is focused on studying the role of promoter-bound transcription initiation factors involved in gene looping. In this study we showed that the RNAP II subunit Rpb4 has a significant effect on termination of transcription. Gene looping is disrupted in the absence of Rpb4. Rpb4 shows a strong physical interaction with the Mediator subunit Srb5. Mediator subunit Srb5 crosslinked to the 5' and 3' ends of INO1 and CHA1 genes and is required for proper termination of transcription of these genes. Srb5 affected termination of transcription through its interaction with the CF1 complex. Srb5 interaction with the CF1 complex as well as its crosslinking to the 3′ end of the genes is dependent on gene looping. Even in the presence of Srb5, proper termination INO1 and CHA1 was compromised in the absence of gene looping. These results strongly indicate a role for gene looping in Srb5-mediated termination of transcription. More importantly, this study has identified a yet another biological role for gene looping in transcription. The prevalence of gene looping was analyzed by genomewide TFIIB ChIP-Seq. The simultaneous presence of TFIIB on both the promoter and terminator of a gene was taken as a measure of gene looping. Our results suggest that gene looping is not restricted to a few transcriptionally active genes in yeast, but is probably a general feature of actively transcribing genes in budding yeast.

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