DNA Methyltransferases

Enzymatic methylation of the C5-carbon position of cytosine residues in a DNA strand yields 5-methyl-2'-deoxycytidine monophosphate. Enzymes catalyzing this reaction belong to the family methyltransferases (EC 2.1.1, MTs).

Eukaryotic DNA methyltransferase (DNMT) was first cloned and sequenced by Timothy Bestor and Vernon Ingram39 in 1988. They isolated well-resolved peptides from homogeneous DNA methyltransferase purified from mouse ery-throleukemia cells, determined their amino acid sequences by Edman degradation, and used these sequences to design and synthesize a 19-mer oligonucleotide hybridization probe. Screening of 1gt11 cDNA libraries prepared from mouse cells with this probe revealed a predicted nucleotide sequence encoding a polypeptide of 1573 amino acid residues that they named Dnmt1. The murine erythroleukemia cells used as a source of Dnmt1 actually contained three very similar species of the enzyme, but their precise relationship was unclear.

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