Our knowledge of mutagenic processes in cells experiencing stress or non-replicating conditions is limited and controversial. While it is well established that stressed cells activate mechanisms that increase mutagenesis, it remains unclear how these mechanisms bias mutagenesis towards the formation of beneficial mutations that allow cells to escape stress. One consequence of genome-wide hypermutation is the increased risk of genetic load;the point at which increased mutation render cells non-viable. An interesting idea that addresses this dilemma, and the subject of this research, is that a stressed population of cells reduces the risks associated with hypermutable states by differentiating a subpopulation of cells that promotes genetic diversity. These mechanisms producing this kind of mutations are conserved and inform on novel views on the evolutionary process. These processes are also implicated in the acquisition of antibiotic resistance and bypass of the immune response in pathogenic bacteria. In differentiated animal cells, these processes are both beneficial and detrimental. One, they produce genetic diversity, and two they associate with the development of tumors and degenerative diseases. The overall goal of this application is to gain a better understanding on how a population of stressed cells activates cellular mechanisms that produce genetic diversity. The hypothesis under study is that the development of competence (a.k.a. the K- state) in combination with the process of transcription and the transcription-repair coupling factor (TRCF - this factor biases DNA repair systems towards highly transcribed regions) mediates the formation of a cell subpopulation that promotes mutagenesis in B. subtilis. We test this hypothesis using genetic and genomic approaches that examine the accumulation of mutations in stressed cells that develop into the K-state and compare it to non-K cells. The genetic approach uses constructs that experimentally control the development of the K-state and transcription of a gene marker to measure mutagenesis. The genomic approach examines how natural development of the K-state and transcriptional responses during stress shape genomic mutation. Ultimately, this application examines a novel mutagenic mechanism and how it remodels the genome and promotes evolution in response to stress. The long term human health implications of this project are that it studies potential therapeutic targets for the treatment of degenerative and pathogenic diseases.
This application seeks a better understanding of how fundamental cell processes, such as those associated with DNA repair and the formation of differentiated cells, generate mutations in human pathogens and in animal cells. Mutations in bacteria have the potential to produce antibiotic resistance or bypass the immune response. In humans mutations are associated with the formation of cancers and the onset of degenerative diseases.
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