Epigenetics describes a phenomenon of modifications in gene expression caused by heritable, but potentially reversible, alterations in the chromatin structure, DNA methylation, and post-transcriptional effects of small noncoding (micro) RNAs (miRNAs), without changes in the DNA sequence. These mechanisms represent novel targets for polyphenols and other natural products in the prevention and treatment of cancer and other diseases. This chapter summarizes the influence of various classes of polyphenol on the enzymatic activities of major enzymes involved in epigenetic gene regulation: DNA and histone methyltransferases (DNMTs and HMTs), histone acetyltransferases (HATs), histone deacetylases (HDACs), and histone demethylases (HDMs). Inhibitory effects mediated by (-)-epigallocatechin 3-gallate (ECGC) from green tea and the isoflavone genistein from soy in vitro and in vivo are described in detail. Functional consequences on gene expression in cell culture, in rodent models and in human intervention studies, are highlighted.
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