The time course of DNA repair following methyl nitro-nitrosoguanidine (MNNG) treatment of P388F lymphoma cells in culture. I. Alkali dissociable DNA lesions and their restitution.

Abstract

The pattern of formation and rejoining of P388F cell DNA single strand breaks revealed by alkaline sedimentation centrifugation studies following treatment with methyl nitro-nitrosoguanidine (MNNG) has been studied. Three periods of single strand break formation have been recognised, an initial period during the first 4 h where breaks are rapidly formed and rejoined, a second (medial) time range of 10-15 h following treatment and a final stage where the formation of breaks appears to be related to cell killing processes. The initial phase is considered to be due to the production and repair of X-ray like DNA lesions whereas those of the medial time range are more comparable to the enzymatic processes associated with the repair of ultraviolet light-induced damage.