Regulation of DNA Methylation by a Major Folate Enzyme

Medical University Of South Carolina, Charleston SC

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Abstract

DESCRIPTION (provided by applicant): Folate derivatives participate in single-carbon transfer reactions that are vital to intracellular processes. Disruptions of folate metabolism can lead to numerous heterologous diseases, such as cancer and diabetic complications. Changes in folate status are often associated with alterations in DNA methylation, a mitotically heritable modification that can lead to significant changes in gene expression and further promote disease. One of the most abundant folate enzymes, 10-formyltetrahydrofolate dehydrogenase (FDH), catalyzes the NADP-dependent conversion of 10-formyltetrahydrofolate to tetrahydrofolate and carbon dioxide. Two observations have prompted this research proposal: (i) that FDH has a direct effect on intracellular levels of S- adenosyl methionine, the major substrate for DNA methyltransferases, and (ii) that FDH requires modification with a 4'-phosphopantetheine prosthetic group for its catalytic activity. We hypothesize that FDH regulates DNA methylation by controlling availability of carbon groups in the folate pool. We further suggest that catalytically active, phosphopantetheinylated FDH is required to fulfill this regulatory function. We will test and explore these hypotheses through the following specific aims: (1) Determine the effect of FDH expression on genomic DNA methylation. (2) Investigate whether phosphopantetheinylation of FDH is required for its effects on intracellular folate pools and DNA methylation. (3) Evaluate the effect of FDH on gene expression using a microarray approach. Cell culture techniques, enzyme activity assays, immunochemical methods, molecular biology, protein silencing by siRNA, assays to measure intracellular folate pools, high-pressure liquid chromatography, and microarray technologies will all be used to achieve the described aims. This project will offer insight into how folate pools affect DNA methylation status. This particular process may have a relationship to the occurrence of epigenetic disease states, particularly in pathologies associated with folate deficiency and diabetes. Knowledge of FDH metabolism may provide pharmacological therapies capable of adjusting cellular methylation status. PUBLIC HEALTH RELEVANCE: Genetic mutations of proteins related to the vitamin B9 (folate), are associated with diabetic complications. This project will characterize a metabolic process related to folic acid that may provide insight into the prevention or treatment of diabetic disease.