DNMT3B - DNA methyltransferase (or DNMT 3B) proteins are involved in DNA methylation in which a methyl group is added to a cytosine residue on DNA, commonly at the C5 position of a CpG dinucleotide. Three families of DNMTs have been identified: DNMT1, DNMT2, and DNMT3.
The DNMT3 family contains two active methyltransferases, DNMT3A & DNMT3B, and one DNMT3-Like protein (DNMT3L). DNMT3B has been shown to be important in the regulation of specific patterns of DNA methylation, specifically de novo methylation. Methylation of mammalian DNA has long been recognized to play a major role in a number of cellular functions such as embryonic development, genetic imprinting, X chromosome inactivation and the control of gene expression. DNA methylation is generally associated with transcriptional repression. Mutations in the DNMT3B gene cause the immunodeficiency-centromeric instability-facial anomalies (ICF) syndrome.