Characterization of the TET2 demethylation complex
Epigenetics encompasses the cellular mechanisms that affect gene expression without changing an organism’s actual DNA sequence. Currently, there are three main methods of cellular epigenetic gene regulation: histone modifications, DNA modifications, and non-coding RNAs. Histone and DNA modifications are commonly referred to as ‘tags’ and alter the physical and biochemical environment around the residue or base. Tags are recognized or removed by various protein/enzyme ‘readers’ or ‘erasers’ that result in various changes in DNA transcription. One of the most studied epigenetic modifications, methylation at the 5’-position of cytosine, is successively oxidized by the Ten-eleven translocase (TET1, TET2, and TET3) family of enzymes and results in demethylation. TET2 is found in a complex with histone modifying proteins that link demethylation with histone modifications and eventually changes in gene expression. One such protein, O-linked N-acetylglucosamine transferase (OGT), is an enzyme that transfers N-acetylglucosamine (GlcNAc) moieties onto –OH groups of serine and threonine residues. Due to the co-localization of TET2 and OGT on chromatin, we sought to investigate the possibility of GlcNAcylated 5-hydroxymethylcytosine (5-GlcNAc-hmC).