Cellular elongation factor 1δ is modified in cells infected with representative alpha-, beta-, or gammaherpesviruses

Earlier reports (Y. Kawaguchi, R. Bruni, and B. Roizman, J. Virol. 71:1019-1024, 1997; Y. Kawaguchi, C. Van Sant, and B. Roizman, J. Virol. 72:1731-1736, 1998) showed that herpes simplex virus 1 (HSV-1) infection causes the hyperphosphorylation of translation elongation factor 1 delta (EF-1 delta) and that the modification of EF-1 delta is the consequence of direct phosphorylation by a viral protein kinase encoded by the U(L)13 gene of HSV-1. The U(L)13 gene is conserved in members of all herpesvirus subfamilies. Here we report the following. (i) In various mammalian cells, accumulation of the hyperphosphorylated form of EF-1 delta is observed after infection with alpha-, beta-, and gammaherpesviruses, including HSV-2, feline herpesvirus I, pseudorabiesvirus, bovine herpesvirus 1, human cytomegalovirus (HCMV), and equine herpesvirus 2. (ii) In human lung fibroblast cells infected with recombinant HSV-1 lacking the U(L)13 gene, the hypophosphorylated form of EF-1 delta is a minor species, whereas the amount of the hyperphosphorylated form of EF-1 delta significantly increases in cells infected with the recombinant HSV-1 in which U(L)13 had been replaced by HCMV U(L)97, a homologue of U(L)13. These results indicate that the posttranslational modification of EF-1 delta is conserved herpesvirus function and the U(L)13 homologues may be responsible for the universal modification of the translation factor.