Mechanism of CpG DNA Methyltransferases M.SssI and Dnmt3a Studied by DNA Containing 2-Aminopurine

Abstract

Murine DNA methyltransferases Dnmt3a-CD and M.SssI from Spiroplasma methylate cytosines at CpG sites. The role of 6-oxo groups of guanines in DNA methylation by these enzymes has been studied using DNA substrates, which contained 2-aminopurine at different positions. Removal of the 6-oxo group of the guanine located adjacent to the target cytosine in the CpG site dramatically reduces the stability of the methyltransferase–DNA complexes and leads to a significant decrease in the methylation. Apparently, O6 of this guanine is involved in the recognition of CpG sites by the enzymes. Cooperative binding of Dnmt3a-CD to 2-aminopurine-containing DNA and the formation of nonproductive enzyme–substrate complexes were observed.

Keywords:

• Eukaryotic and prokaryotic DNA methyltransferases
• 2-aminopurine
• guanine 6-oxo group
• DNA binding and methylation
• molecular mechanism

Acknowledgments

We thank A. Jeltsch for providing the plasmid containing the Dnmt3a-CD gene, B. Jack (New England BioLabs) for the plasmid containing the M.SssI gene, and M.V. Darii for valuable discussions. This research was supported by Russian Foundation for Basic Research (RFBR) grant 10-04-00809.