An anomalous effect of hydroxyurea and visible light on nucleic acids of a photoreactivating mammalian cell Potorous tridactylis.

Abstract

Potorous tridactylis,we have observed an unusual synergistic effect of hydroxyurea (HU) and visible light on nucleic acid synthesis . This effect occurs after removal of HU from the medium and does not seem to be directly related to its well-known direct effect on DNA synthesis. Because the effect does not occur in mouse L cells, which do not perform PR, the observation suggests an interaction of HU with the chromophore of the system responsible for PR . Cook and Regan (1969) reported that cultured cells of P .tridactyliscontain PR enzymes, as assayed by several tests . The line we have used is also capable of PR, as measured by reversal of dimers induced in the DNA by a 12 hour incubation in the presence of white light . Samples of DNA labelled with 3HTdR were sent to Dr . James Trosko, Michigan State University, who kindly performed the assays by standard techniques (Trosko, Chu and Carrier 1965). Although they are incomplete, owing to losses during shipment, the data (table 1) with 150 ergs/mm 2 show that the exposure to light reduced the incidence of