DISTURBANCE OF DNA-DAMAGE RECOGNITION AFTER UV-IRRADIATION BY NICKEL(II) AND CADMIUM(II) IN MAMMALIAN

Nickel(II) and cadmium(II) have been shown previously to inhibit the i ncision step of nucleotide excision repair. By applying a gel-mobility -shift assay and HeLa nuclear extracts the effect of both metals on th e damage recognition step of the repair process was investigated. Two proteins of 34 and 40 kDa were identified that bind with high affinity to a UV-irradiated synthetic oligonucleotide. When applying nuclear e xtracts from HeLa cells treated with 50 mu M nickel(II) and higher, th ere was a dose-dependent decrease in protein binding; this effect was largely reversible by the addition of magnesium(II) to the binding rea ction. In the case of cadmium(II), a dose-dependent inhibition of DNA- protein interactions was detected at 0.5 mu M and higher, which was al most completely reversible by the addition of zinc(II). Therefore, com pounds of both metals disturb DNA-protein interactions essential for t he initiation of nucleotide excision repair most likely by the displac ement of essential metal ions.