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ADDz domain found in DNA (cytosine-5) methyltransferases (C5-MTases) 3 (Dnmt3) Dnmt3 is a de novo DNA methyltransferase family that includes two active enzymes Dnmt3a and -3b and one regulatory factor Dnmt3l. The ADDz domain of Dnmt3 is located in the C-terminal region of Dnmt3, which is an active catalytic domain in Dnmt3a and -b, but lacks some residues for enzymatic activity in Dnmt3l. DNA methylation is an important epigenetic mechanism involved in diverse biological processes such as embryonic development, gene expression, and genomic imprinting. The ADDz_Dnmt3 domain is a PHD-like zinc finger motif that contains two parts, a C2-C2 and a PHD-like zinc finger. PHD zinc finger domains have been identified in more than 40 proteins that are mainly involved in chromatin mediated transcriptional control; the classical PHD zinc finger has a C4-H-C3 motif that spans about 50-80 amino acids. In ADDz, the conserved histidine residue of the PHD finger is replaced by a cysteine, and an additional zinc finger C2-C2 like motif is located about twenty residues upstream of the C4-C-C3 motif.
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