Chapters authored
Hydroxymethylation Influences on Intestinal Epithelial Cells in Health and Disease
Epigenetics describes modifications that affect gene expression that are not encoded within the DNA sequence. DNA methylation is the longest appreciated epigenetic modification and has been accepted to play a critical role in maintaining euchromatin and silencing genes. Recently, a separate and distinct covalent modification has been recognized; hydroxymethylation, which has been associated with increased gene expression as opposed to gene silencing. However, traditional methods to study DNA methylation also recognized hydroxymethylation and did not distinguish between these two distinct DNA covalent modifications. Furthermore, TET enzymes have been identified to play a critical role in active hydroxymethylation of previously methylated cytosine residues and may further result in conversion to cytosine. TET1 plays a critical role in intestinal epithelial differentiation and development, and this is also correlated with increased hydroxymethylation in terminally differentiated epithelial cells. Colon cancer, which arises from the colonic epithelium, exhibits decreased hydroxymethylation and altered gene expression.
Part of the book: Gene Expression and Regulation in Mammalian Cells