Genomic profiling of yeast resistance to heterocylic aromatic amines

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Abstract/Summary Colorectal cancer is the second leading cause of cancer deaths in the United States. Fewer than 5% of colon cancer cases are linked to known high-penetrant genetic factors, while lifestyle factors include a diet high in red meat consumption. Carcinogens found in cooked red meat include heterocyclic aromatic amines (HAAs), which become potent DNA damaging agents after activation by P450 enzymes and N-acetyl transferase 2 (NAT2). However, it is unknown which individuals are most susceptible to HAAs and epidemiological studies often lack significance because of small sampling sizes. Since many DNA metabolism and housekeeping genes are conserved from yeast to man, high-throughput analysis of Saccharomyces cerevisiae (budding yeast) genes that confer resistance to carcinogens have identified human genes that confer resistance to environmental carcinogens. Genomic phenotyping using the ~5,000 yeast single-gene deletion haploid and diploid strains have been highly successful in determining genes that confer resistance to chemical agents. We previously were successful in introducing human CYP1A2 and CYP1A1 into yeast and activating a variety of carcinogens, including aflatoxin B1 (AFB1), benzo[a]pyrene dihydrodiol (BaP-DHD), and HAAs. The aim of this project is to determine which yeast genes are required for resistance to the potent HAA carcinogens. We will introduce plasmids that express human CYP1A2 and NAT2 into the ~5,000 diploid homozygous single-deletion strains. In the first aim, we will profile the yeast genome using the diploid single deletion strains for resistance to HAAs. Genes that confer resistance will be identified by high-throughput sensitive assays to measure cell growth and by molecular bar codes using high throughput sequencing. Considering that CYP1A2 is mostly expressed in the liver and not the colon, in the second aim, we will identify which colon-associated CYPs can metabolically activate HAAs. The information resulting from this project will aid health care providers in identifying individuals most at risk for colon cancer due to dietary carcinogens. The project will be a valuable training tool for graduate and undergraduate students in systems and cell biology.