Purification and characterization of XXXX DNA methyltransferases by use of monoclonal antibodies.

@entity1 @entity9600 @entity3208 @entity19 @entity10918 @entity377 @entity3874 @entity5498 @entity2975
Previously, we have derived @entity19 hybridomas producing monoclonal antibodies against DNA methyltransferase from @entity1 placenta (Kaul, S., Pfeifer, G. P., and Drahovsky, D. (1984) Eur. J. Cell Biol. 34, 330-335). One of these monoclonal antibodies, M2B10, which undergoes immune complex formation also with DNA methyltransferase from @entity19 @entity19 @entity9600 cells, was used for the immunoaffinity purification of @entity19 and @entity1 DNA methyltransferases. In @entity3208 - @entity2975 gels and in immunoblotting studies, the immunoaffinity-purified @entity19 DNA methyltransferase revealed 5-6 polypeptides of molecular masses 150-190 kDa. The immunoaffinity-purified @entity1 placental DNA methyltransferase was characterized by a polypeptide of 158 kDa, presumably representing the native enzyme molecule and by polypeptides of 105-108 kDa and 50-68 kDa, probably generated by a limited proteolysis of the native enzyme molecule. The immunoaffinity-purified DNA methyltransferases preferred hemimethylated DNA substrates over unmethylated ones, and among all unmethylated substrates tested, @entity10918 .(dG-dC)] had the highest @entity5498 -accepting activity. DNA polymers of at least 90 base pairs in length were required for the binding reaction of the immunoaffinity-purified @entity1 DNA methyltransferase, and this initial binding was apparently independent of the @entity377 composition of the DNA polymer and of the presence of @entity3874 .
