P-228 - Nitric oxide is an epigenetic regulator of gene expression by directly controlling DNA methylation patterns

Abstract

Previously we demonstrated that nitric oxide (NO) could inhibit the catalytic activity and expression levels of JmjC-domain containing histone demethylases which resulted in significant changes in histone posttranslational modifications. Current studies investigated whether NO could similarly inhibit Ten Eleven Translocation (TET) enzymes which belong to the same family of mononuclear non-heme iron dioxygenases. TET proteins are involved in DNA demethylation by catalyzing the successive oxidation of 5-methylcytosine (5mC) to 5-hydroxy- (5hmC), 5-formly, and 5-carboxy-. Cancer cells treated with physiologic concentrations of NO demonstrated differential changes in TET mRNA/protein expression levels for all three isoforms. We measured changes in 5mC oxidation products in response to NO and found that global levels of 5hmC were markedly decreased in the NO treated cells suggesting inhibition of TET activity. Measurement of TET enzyme activity following cellular NO exposed demonstrated a significant decrease in activity which was by supported by EPR studies showing that NO could directly bind to catalytic non-heme iron. Lastly, the enrichment of 5mC/5hmC at specific NO-regulated genes correlated to changes in their expression indicating a novel mechanisms of gene regulation by NO.