The role of error-prone polymerases in mutagenesis and evolution

Vanderbilt University, Nashville TN

Investigators

Abstract

Project Summary Mutations are the ultimate source of genetic variation in all organisms and, coupled with natural selection, shape the natural world and are responsible for the biodiversity we enjoy today. However, mutations are crucial for human health and disease. It is mutations that allow bacteria to become resistant to antibiotics and cancer cells to chemotherapy. However, what cellular processes promote spontaneous mutagenesis, and therefore drive evolution, as well as the role of the environment in this process, remains poorly understood. We have shown that error-prone DNA polymerases promote mutations and the evolution of antibiotic resistance in bacteria. Importantly, this is dependent on a DNA repair pathway called transcription-coupled repair, that depends on transcription, but it is independent of replication. This is in contrast with the most well-known mechanisms of mutagenesis, which depend on replication. Because the chemical makeup of the environment in which different bacteria are found can dramatically affect the sources of DNA damaged that they are exposed to, I hypothesize that it will have a strong influence on this pro-mutagenic process. The goal of this proposal is to describe how bacterial error-prone polymerases promote transcription associated mutagenesis and the evolution of antibiotic resistance, as well as how the environment in which bacteria live affects this process. For the K99-phase of the proposal, I will characterize the molecular mechanism by which these polymerases promote transcription associated mutagenesis (Aim1), and which types of mutations these polymerases make in model bacteria (Aim2). At the same time, I will learn the necessary skills to study this process in different medically relevant bacterial species. With these new skills, during the R00 phase of the proposal I will determine which types of transcription associated mutations most commonly arise in highly divergent bacteria that are found in different environments (Aim2). In addition, I will determine the evolutionary history of these pro-mutagenic polymerases to find out how their environment has shaped the way they have evolved (Aim3). In addition, I will establish the role of error-prone polymerases in driving bacterial evolution, antibiotic resistance, and pathogenicity (Aim3). This research as well as my career development plan will take part at Vanderbilt University, in the laboratory of Dr. Houra Merrikh. Dr. Merrikh has a track record of doing groundbreaking work on the mechanisms of mutagenesis and the evolution of antibiotic resistance. During my time in her lab, I will benefit from her expertise and scientific knowledge. The work pertaining to Aim3 will be done with the assistance of my collaborator Dr. Antonis Rokas of Vanderbilt University, which is an expert in the study of evolution. The novel skills I will learn during my time at Vanderbilt University will help me establish an independent research program. Overall, this K99/R00 proposal will allow me to successfully transition from a mentored scientist into a successful independent researcher, while providing key insights on how the environment affects bacterial evolution and antibiotic resistance.