You are here
Control of PKR protein kinase by hepatitis C virus nonstructural 5A protein: molecular mechanisms of kinase regulation.
Title | Control of PKR protein kinase by hepatitis C virus nonstructural 5A protein: molecular mechanisms of kinase regulation. |
Publication Type | Journal Article |
Year of Publication | 1998 |
Authors | Gale, M, Blakely, CM, Kwieciszewski, B, Tan, SL, Dossett, M, Tang, NM, Korth, MJ, Polyak, SJ, Gretch, DR, Katze, MG |
Journal | Mol Cell Biol |
Volume | 18 |
Issue | 9 |
Pagination | 5208-18 |
Date Published | 1998 Sep |
ISSN | 0270-7306 |
Keywords | Animals, Base Sequence, Binding Sites, Cloning, Molecular, COS Cells, Dimerization, DNA Primers, eIF-2 Kinase, Escherichia coli, Gene Expression Regulation, Enzymologic, Hepacivirus, Interferons, Models, Biological, Molecular Sequence Data, Mutagenesis, Site-Directed, Point Mutation, Polymerase Chain Reaction, Recombinant Proteins, RNA Replicase, Sequence Deletion, Transfection, Viral Nonstructural Proteins, Virus Replication |
Abstract | The PKR protein kinase is a critical component of the cellular antiviral and antiproliferative responses induced by interferons. Recent evidence indicates that the nonstructural 5A (NS5A) protein of hepatitis C virus (HCV) can repress PKR function in vivo, possibly allowing HCV to escape the antiviral effects of interferon. NS5A presents a unique tool by which to study the molecular mechanisms of PKR regulation in that mutations within a region of NS5A, termed the interferon sensitivity-determining region (ISDR), are associated with sensitivity of HCV to the antiviral effects of interferon. In this study, we investigated the mechanisms of NS5A-mediated PKR regulation and the effect of ISDR mutations on this regulatory process. We observed that the NS5A ISDR, though necessary, was not sufficient for PKR interactions; we found that an additional 26 amino acids (aa) carboxyl to the ISDR were required for NS5A-PKR complex formation. Conversely, we localized NS5A binding to within PKR aa 244 to 296, recently recognized as a PKR dimerization domain. Consistent with this observation, we found that NS5A from interferon-resistant HCV genotype 1b disrupted kinase dimerization in vivo. NS5A-mediated disruption of PKR dimerization resulted in repression of PKR function and inhibition of PKR-mediated eIF-2alpha phosphorylation. Introduction of multiple ISDR mutations abrogated the ability of NS5A to bind to PKR in mammalian cells and to inhibit PKR in a yeast functional assay. These results indicate that mutations within the PKR-binding region of NS5A, including those within the ISDR, can disrupt the NS5A-PKR interaction, possibly rendering HCV sensitive to the antiviral effects of interferon. We propose a model of PKR regulation by NS5A which may have implications for therapeutic strategies against HCV. |
Alternate Journal | Mol. Cell. Biol. |
PubMed ID | 9710605 |