Research Areas

DNA Damage Management & Genetic Instability

Transcriptional Mutagenesis

Exploiting Yeast as an Informative Tool for Antitumor Agent Identification and Evaluation

Microarray Analysis
of Yeast Cells

Interconnections: DNA Damage Management Pathways
The emphasis of this area is to gain an understanding of the interrelationships between DNA repair, damage tolerance, and other pathways that exist in eukaryotic cells for resisting genetic damage. Eukaryotes have evolved several pathways for reversing and/or coping with DNA damage, including base excision repair (BER), nucleotide excision repair (NER), translesion synthesis (TLS), and recombination (REC). In general, it has previously been thought that the repair of a major part of oxidative and alkylations DNA damage from environmental agents and endogenous sources has primarily been mediated by the BER pathway. Using baker's yeast, Saccharomyces cerevisiae as a model eukaryotic system to study the repair of oxidative DNA damage, we have found that there is considerable overlap between the BER, NER, TLS and REC pathways with respect to damage processing. Mutants with both BER and NER defects show enormous elevations in both spontaneous mutation and recombination rates. These results indicate probably interactions between various DNA excision repair and damage tolerance pathways in eukaryotic cells in response to exogenous and endogenous sources of oxidative and alkylation agent-induced DNA damage. Our current studies are aimed at further dissection of the underlying pathway interconnections between the BER, NER, TLS and REC systems operating in the yeast nucleus and the BER and REC systems operating in yeast mitochondria which respond to and affect the cytotoxic, mutagenic, and recombinogenic actions of certain environmental and endogenous oxidative DNA damaging agents. (back to top)

Transcriptional Mutagenesis
This group is concerned with an RNA-centric model for how new mutant proteins can arise in cells independently of DNA replication or cell division. RNA polymerases possess the ability to transcribe past a variety of different types of DNA damages on the template strand resulting in base misincorporations in the RNA product. This process, which we term transcriptional mutagenesis, has been demonstrated (by us and other groups) for a number of different in vitro transcription systems. If transcriptional mutagenesis takes place in living cells, it could provide a major route for the generation of mutant proteins, particularly in non-dividing cells. We are investigating the degree to which transcriptional mutagenesis occurs in the three different model systems (bacterial, yeast and mammalian cells) possessing different DNA repair capabilities. The goals of these studies are to define which types of genetic damage are the most potent inducers of transcriptional mutagenesis as measured by changes in cellular phenotype. These studies also address the likelihood of transcriptional mutagenesis in the etiology of human cancer, neurological, and other degenerative diseases. (back to top)

Exploiting Yeast as an Informative Tool for Antitumor Agent Identification and Evaluation
The goal of these studies is to exploit the similarity of DNA damage management pathways between humans and the model organism Saccharomyces cerevisiae to rapidly screen anticancer agents. Screening anticancer agents against yeast strains that are defective in one or a combination of two DNA damage management pathways allows us to determine the relative contribution of each repair or tolerance pathway to processing the damage induced by the agent. The efficacy of many anticancer agents depends on the ability of cancer cells to repair or tolerate the damage initiated by drugs, therefore it is important to identify those pathways responsible for processing anticancer drug induced DNA lesions. Due to the conservation of DNA damage management pathways, the knowledge gained in these yeast studies towards understanding the mechanisms of DNA damage processing in response to cytotoxic agents has significance for predicting chemotherapy resistance and response to treatment in humans. Additionally, the pathways that when impaired sensitize yeast to anticancer agents may be important predictive indicators of efficacy in tumor cells with different DNA repair capabilities. (back to top)