Antibodies specific for methylated DNA elicited in rabbits recognize only a single strand region of DNA containing 7-methylguanine.

Abstract

Immunogenicity of methylated DNA (Me-DNA) was investigated in connection with the changes of the high order structure. Antibodies specific for Me-DNA were elicited in the rabbits with DNA methylated at different extents. When Me-DNA was chromatographed on a hydroxyapatite column and was separated into single and double stranded forms, Me-DNA eluted at single strand position was found to react only with the anti-Me-DNA antibodies. In order to examine the immunogenicity of both single and double stranded forms, each form was injected in rabbits respectively. No specific antibodies were produced for the double stranded form, whereas the single stranded form showed a potent immunogenicity. On the other hand, the antigenicity of the single stranded Me-DNA was decreased or lost in parallel with the extent of the release of 7-methylguanine residues from the molecule on heating under the neutral condition. These results revealed that single stranded structure of Me-DNA is immunogenic or antigenic and that 7-methylguanine residues of Me-DNA play an important role in forming a characteristic structure required for the manifestation of its specific antigenicity.