n-phenyl-n--3-hydroxyphenylthiourea and Carcinoma--Krebs-2

PTU-23, an effective in vivo wide-range enterovirus inhibitor, suppresses the reproduction of encephalomyocarditis (EMC) virus in Krebs-II ascites carcinoma cells at concentrations of 20-50 micrograms/ml, not affecting the cellular synthetic processes. The virus-specific RNA synthesis is distinctly inhibited. The studies on the kinetics of this effect point to its leading role in the inhibitory action the compound exerts on the production of infectious virions. The sedimentation profile in sucrose density gradient of the viral RNA isolated from PTU-23-treated cells by phenol extraction shows a clear inhibition of the synthesis of the single-stranded (ss) 37S RNA and to a lesser extent of the double-stranded (ds, RF) 20S RNA. The effect of the inhibitor on the RNA-dependent RNA polymerase in a cell-free RNA-synthesizing system has been studied, using an an enzyme preparation the 40000 g fraction of a nuclear-free extract from infected Krebs-II cells, containing the enzyme bound to the endogenous RNA template. It is established that the compound does, not affect the synthesis of the enzyme which could be probably explained by the incomplete (45-70%) inhibition of the viral RNA synthesis, its translatory function remaining unperturbed. The observed insignificant inhibition (20-26%) of the enzyme activity during the application of the inhibitor to the RNA-synthesizing reaction mixture cannot explain its effect on the viral RNA synthesis. An interaction of PTU-23 with another virus-specific protein component of the replication complex is suggested.

Topics: Animals; Antiviral Agents; Carcinoma, Krebs 2; Cells, Cultured; Encephalomyocarditis virus; Female; Mice; Neoplasm Proteins; Phenylthiourea; RNA-Dependent RNA Polymerase; RNA, Neoplasm; RNA, Viral; Virus Replication

PTU-23, a selective inhibitor of the reproduction of encephalomyocarditis (EMC) virus in Krebs-II ascites carcinoma cells, counteracts the virus-induced shut-off of the host-cell protein synthesis reducing it from 32% to 19%. The compound does not inhibit the synthesis of virus-specific proteins; the electrophoretic profile in SDS-PAAG shows an increase in the peaks of some viral polypeptides, mainly A, E and epsilon. It is suggested that this effect is connected to the partial inhibition by PTU-23 of the synthesis of the viral 37S RNA, without affecting its translation activity and also to the inhibition of the synthesis of 20S (RF) RNA--an inhibitor of the virus-specific protein synthesis. PTU-23 does not affect the processing of the high-molecular-weight viral precursor polypeptide preA, which is carried out by the virus-specific protease protein p22, as shown in studies with a cell-free system.

Topics: Animals; Antiviral Agents; Carcinoma, Krebs 2; Cells, Cultured; Electrophoresis, Polyacrylamide Gel; Encephalomyocarditis virus; Mice; Neoplasm Proteins; Phenylthiourea; Viral Proteins