Regulation of herpesvirus macromolecular synthesis V. Properties of α polypeptides made in HSV-1 and HSV-2 infected cells

Abstract

Previous reports from this laboratory have defined as α those viral polypeptides whose production in infected cells does not require prior protein synthesis. Two subsequent groups, β and γ, depend on prior a and β polypeptide synthesis, respectively. Comparison of the synthesis and properties of a polypeptides specified by herpes simplex viruses (HSV) 1 and 2 showed the following: (i) The three earliest virus-specific infected cell polypeptides (ICP) made in HSV-2 infected cells migrated slightly more slowly in polyacrylamide gels than the HSV-1 α polypeptides, ICP 4.0 and 27. (ii) Cells treated with canavanine from the time of infection with HSV-2 produced all α, a subset of β, and a small amount of one γ polypeptide; the synthesis of these polypeptides continued for many hours, at rates related to the multiplicity of infection. The transition from a to this subset of β polypeptide synthesis did not appear to be affected by the arginine analogue, whereas transition to the other sets of β and to γ polypeptide synthesis was blocked. A similar discrimination between different subsets of β proteins was seen in treated HSV-1 infected cells. (iii) All a and a number of β polypeptides observed in this study underwent translocation into the nucleus, posttranslational modification resulting in a reduced electrophoretic mobility, and phosphorylation. For example, the modification of HSV-1 and HSV-2 ICP 4 was in at least two steps from the translational product ICP 4a, labeled during a pulse, to slower-migrating forms ICP 4b and 4c. All three forms were phosphorylated but only 4b and 4c were found in the nucleus. In untreated infected cells, ICP 4 ultimately accumulated in form ICP 4c. ICP 4a made in the presence of canavanine was not processed efficiently into ICP 4c. In another instance, the polypeptide made in the presence of canavanine were not translocated into nuclei.