Factors regulating cellular DNA synthesis induced by adenovirus infection. II. The effects of actinomycin D on productive virus-cell systems.

Abstract

Abstract The effect of a low dose of actinomycin D on human and hamster cells productively infected with adenovirus types 2 (Ad2) and 12 (Ad12) was studied. In the productive infection of G1-arrested BHK21 cells with Ad2, 0.03 μg/ml of AMD reduced the virus yield by >90%, but the number of cells synthesizing T antigen was not affected. Unlike Ad12-infected BHK21 cells ( Laughlin and Strohl, 1976 ), the virus-induced cycle of DNA synthesis was markedly refractory to inhibition by 0.03 μg/ml of AMD. Centrifugation and DNA-DNA hybridization analysis showed this to be the result of inhibition of free viral DNA synthesis and induction of cellular DNA synthesis. The sensitivity of Ad2 and Ad12 virus replication in WI-38 cells was similar to that of Ad2 in BHK21. While total DNA synthesis did not exhibit refractoriness to AMD, drug treatment did induce a shift in Ad2-infected cells towards increased synthesis of high molecular weight DNA as viral DNA was increasingly inhibited. A similar increase in WI-38 cell DNA synthesis was not produced by AMD-treatment of Ad12-infected cells, although cellular DNA synthesis in infected cells was less sensitive to AMD than was uninfected WI-38 cell DNA synthesis. To account for the great diversity in response to AMD depending on cell species and virus type, it is proposed that virus infection stimulates both normal replicative DNA synthesis, which requires an AMD-sensitive function in G1 in order to proceed from G1 into S, as well as AMD-insensitive synthesis which is due specifically to the virus infection, and which does not require the AMD-sensitive G1 function.