Suppression of UV mutagenicity by human interferon

Effects of human interferon (HuIFN)-alpha on UV mutagenicity were examined in a human cell strain, RSa, and xeroderma pigmentosum (XP)-derived fibroblasts (XP1KY). The frequency of ouabain-resistance mutation in UV-irradiated RSa cells was unusually high (Suzuki et al., 1985), but that in cells pretreated with HuIFN-alpha before irradiation was reduced. 6-Thioguanine-resistance mutation was also depressed in XP1KY cells treated with HuIFN-alpha before irradiation. However, the depression of UV mutagenicity by HuIFN-alpha was lessened by treatment with cycloheximide immediately after UV irradiation. The relationship between HuIFN-depressed UV mutagenicity and HuIFN-affected DNA-repair and repair-related functions is discussed.