Advisory Committee Chair
Advisory Committee Members
Date of Award
Degree Name by School
Doctor of Philosophy (PhD) School of Medicine
In contrast to Bacteria and Archaea that express a single DNA-dependent RNA polymerase (RNAP), eukaryotes express at least three structurally distinct, nuclear, DNA-dependent RNA polymerases (Pols I, II, and III) that are responsible for synthesizing all the genome-encoded RNA required by the cell. Despite the discovery of the Pols over 50 years ago, there remains a knowledge gap concerning their enzymatic properties. Over the course of evolution, we know that Pols I, II, and III have diverged in structure and function. They share a 10-subunit core and are each responsible for transcribing unique genetic loci. What remains to be understood is how these molecular machines compare under identical experimental conditions. Using the same in vitro strategy, we reveal key biochemical differences in the transcription elongation phase of Pols I, II, and III that would otherwise be impossible to elucidate in lieu of an identical experimental method. We find that Pols I, II, and III possess distinct biochemical properties that we theorize further specialize them for their unique cellular roles. Our investigation of the Pols is not only critical to our fundamental understanding of eukaryotic gene expression, but also illustrates how uncovering the biochemical differences between the Pols can be exploited for therapeutic gain. In the last two decades, Pol I has emerged as a chemotherapeutic target due to its pivotal role in ribosome biogenesis. Cancer cells upregulate Pol I activity to drive ribosome abundance which is required for tumorigenesis and metastasis. Multiple groups are pursuing the discovery of novel Pol I-targeting molecules to specifically inhibit Pol I transcription. The derivatives of one promising molecule, BMH-21, are currently in pre-clinical development. We elucidate BMH-21’s mechanism of action and further show that Pol I, in comparison to Pols II and III, is the most vulnerable Pol to its inhibitory effects. We argue that Pol I’s unique biochemical properties we previously revealed are responsible for sensitizing it to BMH-21 treatment. Overall, this dissertation uncovers the unique biochemical properties of Pols I, II, and III and demonstrates how those findings can be exploited in current and future Pol I-targeting chemotherapeutic endeavors.
Jacobs, Ruth Qian, "Biochemical Characterization of RNA Polymerases I, II, and III and Its Therapeutic Implications" (2023). All ETDs from UAB. 37.