Inactivation of the shutoff gene (UL41) of herpes simplex virus types 1 and 2

Gene UL41 of herpes simplex virus type 1 (HSV-1) and the corresponding gene of HSV-2, which control the virion-mediated early suppression of cellular protein synthesis, have been inactivated by inserting a beta-galactosidase expression cassette into their coding regions. The resulting recombinants grew well in tissue culture, although with the type 2 recombinant viral protein synthesis was slightly delayed. As a result of inactivation of UL41 host protein synthesis was not suppressed in the presence of actinomycin or early in normal infection, although it declined at a late stage. Polyribosomes were not broken down early in infection, cellular DNA synthesis was not inhibited and in the presence of cycloheximide stable alpha (immediate early) mRNA accumulated, in marked contrast to that of the parent HSV-2 strain. Comparison of the proteins of purified virions of HSV-1 and shutoff-defective recombinant virus revealed discrepancies consistent with the presence of the UL41 gene product in the enveloped virion.