Prolonged ultraviolet-induced thymidine incorporation into xeroderma pigmentosum lymphocytes: Studies on its duration, amount, localization and relationship to hydroxyurea

Abstract

Xeroderma pigmentosum lymphocytes which have a lower than normal rate of ultraviolet-induced [ 3H]thymidine incorporation during the hours immediately after irradiation continue their incorporation for a longer time than normal lymphocytes. This difference in the duration of incorporation into xeroderma pigmentosum and normal lymphocytes is not caused by the continuous presence of hydroxyurea in the cultures. The prolonged incorporation ceases after the xeroderma pigmentosum lymphocytes have incorporated as much thymidine as normal lymphocytes. Autoradiograms show that the prolonged incorporation is nuclear and occurs in the majority of lymphocytes. The results indicate that these xeroderma pigmentosum lymphocytes can perform as much repair of ultraviolet-damaged DNA as normal lymphocytes but require a longer period in which to do so.