Monoclonal antibodies recognize different parts of Z-DNA.

Brominated poly(dG-dC) . poly(dG-dC), which forms a stable Z-DNA helix under physiological salt conditions, was used as an antigen to produce monoclonal antibodies from mice. The anti-Z-DNA antibodies were specific for the Z conformation as was shown by direct binding studies and a competitive solid phase assay. Competition could only be seen by brominated poly(dG-dC) . poly(dG-dC) under low and high salt conditions and unmodified poly(dG-dC) . poly(dG-dC) under high salt conditions. No binding could be seen to a number of other polynucleotides, including native and denatured DNA. Among the anti-Z-DNA monoclonal antibodies, examples differed in specificity: binding of one monoclonal antibody was blocked by methylation of cytosine; whereas the other antibody reacted equally well with the unmodified polymer or methyl cytosine-containing polymer in high ionic strength. The two antibodies are specific for different localized features of Z-DNA structure.