Variola virus E3L Z? domain, but not its Z-DNA binding activity, is required for PKR inhibition.

Responding to viral infection, the interferon-induced, double-stranded RNA (dsRNA)-activated protein kinase PKR phosphorylates translation initiation factor eIF2? to inhibit cellular and viral protein synthesis. To overcome this host defense mechanism, many poxviruses express the protein E3L, containing an N-terminal Z-DNA binding (Z?) domain and a C-terminal dsRNA-binding domain (dsRBD). While ...
E3L is thought to inhibit PKR activation by sequestering dsRNA activators and by directly binding the kinase, the role of the Z? domain in PKR inhibition remains unclear. Here, we show that the E3L Z? domain is required to suppress the growth-inhibitory properties associated with expression of human PKR in yeast, to inhibit PKR kinase activity in vitro, and to reverse the inhibitory effects of PKR on reporter gene expression in mammalian cells treated with dsRNA. Whereas previous studies revealed that the Z-DNA binding activity of E3L is critical for viral pathogenesis, we identified point mutations in E3L that functionally uncouple Z-DNA binding and PKR inhibition. Thus, our studies reveal a molecular distinction between the nucleic acid binding and PKR inhibitory functions of the E3L Z? domain, and they support the notion that E3L contributes to viral pathogenesis by targeting PKR and other components of the cellular anti-viral defense pathway.
Mesh Terms:
Amino Acid Sequence, Amino Acid Substitution, DNA, Z-Form, HeLa Cells, Host-Pathogen Interactions, Humans, Immunity, Innate, Molecular Sequence Data, Mutagenesis, Site-Directed, Point Mutation, Protein Binding, Protein Structure, Tertiary, RNA, Double-Stranded, RNA-Binding Proteins, Saccharomyces cerevisiae, Variola virus, Viral Proteins, eIF-2 Kinase
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Date: Feb. 01, 2014
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