Effects of Inhibition of Protein Synthesis on Adenovirus 5 Early Gene Expression

Abstract

Previous studies have shown that a functional Ad 5 E1A protein from the 13 S mRNA is required during lytic infection for activation of early viral gene expression (Jones and Shenk, 1979b; Berk et al, 1979; Montell et al, 1982). The mechanism by which E1A exerts this regulatory function is still unclear and has been the subject of intense investigation (Persson et al, 1981a; Katze et al, 1981, 1983; Nevins, 1981; Shaw and Ziff, 1982). Most of these recent investigations have relied on the use of metabolic inhibitors such as cycloheximide to eliminate protein synthesis as a means of determining the role of viral and host proteins in the regulatory process. The results from these studies have been inconsistent. The purpose of this research project has been to re-examine the regulation of Ad 5 early gene expression without the use of drug inhibitors. In this study tsH1 cells, a mutant CHO cell line which at temperatures above 37°C are inhibited in protein synthesis, were used. At critical times during the course of wild type or host-range 1 infection of tsH1 cells, protein synthesis was inhibited and Early Region 4 expression was examined. In every case, efficient E4 expression was dependent on functional E1A protein and this requirement could not be replaced by simply inhibiting protein synthesis. The results are discussed in relation to models proposed to explain the regulation of Ad 5 Early Gene Expression.