Affinity-Labeling Study for Determining Interacting Sites of an Anti-DNA Antibody on DNA Double Helix

Abstract

Previously, a purified monoclonal mouse (MRL-lpr/lpr) IgG anti-DNA autoantibody, H241, was reported to interact with major groove and possibly with phosphate backbone of synthetic helical oligonucleotide of 18 base pairs in affinity-labeling experiment. Experiments were performed to determine further the interacting sites of the autoantibody, H241, on the DNA double helix. Two oligonucleotides which were specifically modified in the minor groove of double-stranded DNA were cross-linked covalently to H241. The ratio of L chain to H chain cross-linked was decreased with the modified oligonucleotide, compared to that with an unmodified helical oligonucleotide. With the more extensively modified oligonucleotide in the minor groove, the ratio was further decreased. This indicates that the anti-DNA autoantibody, H241, possibly interacts possibly with the minor groove as well.