title: DNA-methylase from regenerating rat liver: purification and characterisation.
abstract: DNA methylase has been purified 660-fold from nuclei from regenerating rat liver. The enzyme is able to methylate single stranded (ss) and double stranded (ds) DNA, the only reaction product being 5-methylcytosine. Previously unmethylated double stranded DNA from prokaryotes (M.luteus) as well as from eukaryotes (Ascaris suis) can serve as substrates. The synthetic copolymers (dG-dC)n . (dC-dG)n and (dG,dC)n are also methylated. While SV40 DNA is almost not methylated, PM2 DNA is a good substrate even in the supercoiled form. The enzyme methylates 1 in 17 bases in heterologous M.luteus DNA, but only 1 in 590 in homologous rat liver DNA. The high methylation level of M.luteus DNA, an analysis of the methylated pyrimidine isostichs and a preliminary dinucleotide analysis suggest that all the CpGs in a DNA can be methylated.
mesh_terms: D000818:Animals; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008115:Liver Regeneration; D008297:Male; D008780:Methyltransferases / Q000378:metabolism*; D009994:Osmolar Concentration; D051381:Rats; D013379:Substrate Specificity
chemical_list: D008780:Methyltransferases; D004248:DNA (Cytosine-5-)-Methyltransferases