The enzymes that catalyze DNA methylation are known as DNA methyltransferases (DNMT) (Goll & Bestor, 2005). Three active mammalian DNMTs have been identified, DNMT1, 3a and 3b. The first identified and most abundant DNMT, DNMT1, otherwise known as a “maintenance methyltransferase,” can recognize hemi-methylated DNA and perform methylation of the complementary strand. The de novo methyltransferases, DNMT3a and DNMT3b, methylate previously unmethylated cytosines, are essential during development and, in the CNS, have been implicated in synaptic plasticity and learning and memory mechanisms (Feng et al., 2010; Levenson et al., 2006; Miller & Sweatt, 2007; Okano, Bell, Haber, & Li, 1999). Disparately, DNMT3l is a protein structurally related to 3a and 3b, but does not have methyltransferase activity on its own and regulates catalytic activities of DNMT3a and 3b (Hata, Okano, Lei, & Li, 2002). Methyl-CpG binding protein 2 (MeCP2) is a protein that binds methylated CpG dinucleotides via interactions through the methyl-CpG-binding domain (MBD) (Lewis et al., 1992; Meehan, Lewis, McKay, Kleiner, & Bird, 1989). It has been shown to both activate and repress transcription (Chahrour et al., 2008; Jones
