The presence of Z-helical conformation in DNA of the calf lens

The purpose of this study was to reveal the presence of Z-helical conformation in normal crystalline lens DNA. Z-DNA antigen was prepared against poly(dG-dC).poly(dG-dC), which had been converted to the Z-helix conformation in high salt and then stabilized by bromination. Circular dichroism (CD) spectra confirmed the presence of left-handed Z-helix DNA. Antibodies to Z-DNA were raised in three rabbits immunized with brominated (Br-) poly(dG-dC).poly(dG-dC). These antibodies do not cross-react with polynucleotides in the B-helical form, but are specific to the left-handed Z-DNA conformation. DNA was isolated from three different regions of the calf lens. Anti-Z-DNA antisera, affinity purified IgG polyclonal anti-Z-DNA antibodies and monoclonal anti-Z-DNA antibodies were used as immunoprobes to detect the presence of S-DNA sequences. DNA from the cortex region of the lens reacted strongly with the anti-Z-DNA antibodies, but no binding could be observed in the DNA from the nucleus region. Digestion of lens DNA with DNase 1 dramatically decreased Z-DNA antibody binding, while RNase A and T1 treatment had no effect on Z-DNA immunoreactivity. This study has demonstrated that: (a) Z-DNA antibodies developed for our study can bind in high salt solutions (4M NaCl) to purified lens DNA sequences isolated from a variety of different calf lens cell types. By this criterion, lens DNA contains sequence determinants which may assume or are in the Z-helix conformation.