Binding properties of bovine ocular lens zeta-crystallin to right-handed B-DNA, left-handed Z-DNA, and single-stranded DNA

Bovine zeta-crystallin has the ability to bind with different DNAs. Initially, this protein was named regulatory factor 36, but it has been shown to be an ocular lens zeta-crystallin, which is considered an enzyme-crystallin. The enzyme-linked immunosorbent assay (ELISA) was used to quantitate the binding of bovine zeta-crystallin to purified high molecular weight double-stranded (ds-) and single-stranded (ss-) DNA (bovine and synthetic DNA). ELISA quantitation was achieved by the addition of anti-zeta-crystallin antibodies to the DNA-zeta-crystallin complex, using a novel immunochemical avidin-biotin method. Zeta-crystallin shows much greater binding intensity for ss-DNA and for ds-Z-DNA than for ds-B-DNA. It also reacts slightly more with ds-Z-DNA than ss-DNA. Therefore, we speculate that zeta-crystallin may act as a transcriptional enhancer (outer lens cortex), possibly binding to Z-DNA regulatory elements within lens crystallin genes. It may also act to protect DNA from endogenous DNase activity and as a DNA unwinding (destabilizing) protein also involved with transcription, occurring in normal adult bovine lens nucleated secondary fiber cells.