Eukaryotic elongation factor 1 delta is hyperphosphorylated by the protein kinase encoded by the U sub(L)13 gene of herpes simplex virus 1

• Published in: Journal of virology 1998-03, Vol.72 (3), p.1731-1736
• Main Authors: Kawaguchi, Y, Van Sant, C, Roizman, B
• Format: Article
• Language: English
• ISSN: 0022-538X

The translation elongation factor 1 delta (EF-1 delta ) consists of two forms, a hypophosphorylated form (apparent M sub(r), 38,000) and a hyperphosphorylated form (apparent M sub(r), 40,000). Earlier Y. Kawaguchi, R. Bruni, and B. Roizman (J. Virol. 71:1019-1024, 1997) reported that whereas mock-infected cells accumulate the hypophosphorylated form, the hyperphosphorylated form of EF-1 delta accumulates in cells infected with herpes simplex virus 1. We now report that the accumulation of the hyperphosphorylated EF-1 delta is due to phosphorylation by U sub(L)13 protein kinase based on the following observations. (i) The relative amounts of hypo- and hyperphosphorylated EF-1 delta in Vero cells infected with mutant virus lacking the U sub(L)13 gene could not be differentiated from those of mock-infected cells. In contrast, the hyperphosphorylated EF-1 delta was the predominant form in Vero cells infected with wild-type viruses, a recombinant virus in which the deleted U sub(L)13 sequences were restored, or with a virus lacking the U sub(S)3 gene, which also encodes a protein kinase. (ii) The absence of the hyperphosphorylated EF-1 delta in cells infected with the U sub(L)13 deletion mutant was not due to failure of post-translational modification of infected-cell protein 22 (ICP22)/U sub(S)1.5 or of interaction with ICP0, inasmuch as preferential accumulation of hyperphosphorylated EF-1 delta was observed in cells infected with viruses from which the genes encoding ICP22/U sub(S)1.5 or ICP0 had been deleted. (iii) Both forms of EF-1 delta were labeled by super(32)P sub(i) in vivo, but the prevalence of the hyperphosphorylated EF-1 delta was dependent on the presence of the U sub(L)13 protein. (iv) EF-1 delta immunoprecipitated from uninfected Vero cells was phosphorylated by U sub(L)13 precipitated by the anti-U sub(L)13 antibody from lysates of wild-type virus-infected cells, but not by complexes formed by the interaction of the U sub(L)13 antibody with lysates of cells infected with a mutant lacking the U sub(L)13 gene. This is the first evidence that a viral protein kinase targets a cellular protein. Together with evidence that ICP0 also interacts with EF-1 delta reported in the paper cited above, these data indicate that herpes simplex virus 1 has evolved a complex strategy for optimization of infected-cell protein synthesis.