Inhibition of UV-induced DNA strand breakage in Dictyostelium discoideum by 2,4-dinitrophenol

In UV-irradiated vegetative cultures of the cellular slime mold Dictyostelium discoideum NC-4, single strand breaks appeared in the DNA very rapidly and at low temperatures (0 to 40C). However, when these cells were incubated, prior to UV irradiation, in the presence of 2mM 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation, breaks did not appear in the DNA. Extracts prepared from cells that had been incubated either in the presence or absence of DNP were tested for endonucleolytic activities on a UV-irradiated exogenous DNA template (phiX-174 RF I). Results suggested that DNP might mediate its effect by interfering with the action of a UV-specific endonuclease. (author)