Ribonucleic Acid Polymerase Induced by Vaccinia Virus: Lack of Inhibition by Rifampicin and α-Amanitin

Abstract

The RNA polymerase activity present in the cytoplasm of BHK cells infected with vaccinia virus is not affected by rifampicin or by a-amanitin. The rifamycins, a group of broad-spectrum antibiotics, have been shown to block bacterial ribonucleic acid (RNA) synthesis (7, 25) by in

Actions of the rifamycins.

“…Early and late proteins are also produced, although synthesis of the latter declines sooner than in the absence of the antibiotic (12,106,107,158), and some variations occur, depending on the virus strain (119,163). Rifampin does not inhibit the RNA polymerase activity of purified vaccinia virus particles (26,101,107,158). The only effect that could be detected was the lack of a particulate RNA polymerase activity, which appears late during virus infection in untreated cells (101).…”

Human cytomegalovirus stimulates host cell RNA synthesis

“…Rifampin derivatives have been reported not to inhibit early mRNA, late mRNA, or viral DNA formation of vaccinia virus (7,18). However, some reports have indicated a partial inhibition of RNA synthesis (5,20). We have observed that there was practically no incorporation of labeled precursor into viral DNA and no production of progeny virus when rifampin was present in the culture medium (100 Ag/ml) (9).…”

Effect of Rifamycins and Related Antibiotics on the Deoxyribonucleic Acid-Dependent Ribonucleic Acid Polymerase of Vaccinia Virus Particles

“…The activity of virion-associated DNA-dependent RNA polymerase was assayed after treatment of the virus with Triton-X-100 and 2-mercaptoethanol. Preliminary testing of the compounds showed that at a concentration of 200 jig/ml, 3-formyl rifamycin SV, AF/ABDP, or DDE exerted a profound inhibitory effect on enzyme activity, comparable to that produced by actinomycin D or Congo red (13) at the same concentration ( Fig. 3).…”

“…One rifamycin derivative, rifampin, has been found specifically to inhibit the growth of vaccinia virus at a late stage, but extensive studies on the nature of this inhibitory action of high concentrations of rifampin have failed to demonstrate that the mechanism of its antiviral action is similar to its antibacterial action (9,18,19,27). The synthesis of viral RNA, DNA, and early and late proteins, though quantitatively affected, is not prevented by inhibitory concentrations of the drug (1, 15 17, 26), and the activity of the virion-associated DNA-dependent RNA polymerase is only slightly inhibited at high concentrations of rifampin (3,15,18,26). Moreover, the virion-associated RNA polymerase of rifampin-resistant mutants of vaccinia virus is inhibited to the same degree as that of wild-type virus by these concentrations of the drug (26).…”