Differential effects of hydroxyurea on the survival of UV- and MNNG-treated adenovirus 5.

The effects of hydroxyurea on plaque formation by UV-irradiated and MNNG-treated adenovirus 5 were investigated. Hydroxyurea blocked the recovery of UV-irradiated viruses in all cases studied, but the effect was less when fibroblasts from a patient with xeroderma pigmentosum were used. This fact supports the notion that hydroxyurea blocks excision repair of UV-produced damage. The recovery of MNNG-treated viruses was not blocked by hydroxyurea when viruses were used to infect normal human fibroblasts, but was blocked if the cell strain used as viral host were deficient in repair of O6-methylguanine. To account for these data, we propose that hydroxyurea blocks repair in which DNA polymerases play a role, but does not block repair in which DNA polymerases are not required.