Identification of a lytic-cycle Epstein-Barr virus gene product that can regulate PKR activation. 2003

Jeremy Poppers, and Matthew Mulvey, and Cesar Perez, and David Khoo, and Ian Mohr
Department of Microbiology and Kaplan Comprehensive Cancer Center, New York University School of Medicine, New York 10016, USA.

The Epstein-Barr virus (EBV) SM protein is a posttranscriptional regulator of viral gene expression. Like many transactivators encoded by herpesviruses, SM transports predominantly unspliced viral mRNA cargo from the nucleus to the cytosol, where it is subsequently translated. This activity likely involves a region of the protein that has homology to the herpes simplex virus type 1 (HSV-1) ICP27 gene product, the first member of this class of regulators to be discovered. However, SM also contains a repetitive segment rich in arginine and proline residues that is dispensable for its effects on RNA transport and splicing. This portion of SM, comprised of RXP triplet repeats, shows homology to the carboxyl-terminal domain of Us11, a double-stranded RNA (dsRNA) binding protein encoded by HSV-1 that inhibits activation of the cellular PKR kinase. To evaluate the intrinsic ability of SM to regulate PKR, we expressed and purified several SM protein derivatives and examined their activity in a variety of biochemical assays. The full-length SM protein bound dsRNA, associated physically with PKR, and prevented PKR activation. Removal of the 37-residue RXP domain significantly compromised all of these activities. Furthermore, the SM RXP domain was itself sufficient to inhibit PKR activation and interact with the kinase. Relative to its Us11 counterpart, the SM RXP segment bound dsRNA with reduced affinity and responded differently to single-stranded competitor polynucleotides. Thus, SM represents the first EBV gene product expressed during the lytic cycle that can prevent PKR activation. In addition, the RXP repeat segment appears to be a conserved herpesvirus motif capable of associating with dsRNA and modulating activation of the PKR kinase, a molecule important for the control of translation and the cellular antiviral response.

UI MeSH Term Description Entries
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D010750 Phosphoproteins Phosphoprotein
D004789 Enzyme Activation Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme. Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D012330 RNA, Double-Stranded RNA consisting of two strands as opposed to the more prevalent single-stranded RNA. Most of the double-stranded segments are formed from transcription of DNA by intramolecular base-pairing of inverted complementary sequences separated by a single-stranded loop. Some double-stranded segments of RNA are normal in all organisms. Double-Stranded RNA,Double Stranded RNA,RNA, Double Stranded
D014764 Viral Proteins Proteins found in any species of virus. Gene Products, Viral,Viral Gene Products,Viral Gene Proteins,Viral Protein,Protein, Viral,Proteins, Viral
D015534 Trans-Activators Diffusible gene products that act on homologous or heterologous molecules of viral or cellular DNA to regulate the expression of proteins. Nuclear Trans-Acting Factor,Trans-Acting Factors,Trans-Acting Factor,Trans-Activator,Transactivator,Transactivators,Factor, Nuclear Trans-Acting,Factor, Trans-Acting,Factors, Trans-Acting,Nuclear Trans Acting Factor,Trans Acting Factor,Trans Acting Factors,Trans Activator,Trans Activators,Trans-Acting Factor, Nuclear
D016601 RNA-Binding Proteins Proteins that bind to RNA molecules. Included here are RIBONUCLEOPROTEINS and other proteins whose function is to bind specifically to RNA. Double-Stranded RNA-Binding Protein,Double-Stranded RNA-Binding Proteins,ds RNA-Binding Protein,RNA-Binding Protein,ds RNA-Binding Proteins,Double Stranded RNA Binding Protein,Double Stranded RNA Binding Proteins,Protein, Double-Stranded RNA-Binding,Protein, ds RNA-Binding,RNA Binding Protein,RNA Binding Proteins,RNA-Binding Protein, Double-Stranded,RNA-Binding Protein, ds,RNA-Binding Proteins, Double-Stranded,ds RNA Binding Protein
D019892 eIF-2 Kinase A dsRNA-activated cAMP-independent protein serine/threonine kinase that is induced by interferon. In the presence of dsRNA and ATP, the kinase autophosphorylates on several serine and threonine residues. The phosphorylated enzyme catalyzes the phosphorylation of the alpha subunit of EUKARYOTIC INITIATION FACTOR-2, leading to the inhibition of protein synthesis. Protein Kinase PKR,Protein Kinase, RNA Activated,RNA-Dependent Protein Kinase,p68 Kinase,DAI Protein Kinase,DSRNA-Dep Protein Kinase,Double Stranded RNA-Dependent Kinase (dsl),Double Stranded RNA-Dependent eIF-2 alpha Protein Kinase,Eukaryotic Initiation Factor 2alpha Kinase,Heme Controlled Repressor,Heme-Controlled Inhibitor,Heme-Controlled Translational Repressor,Heme-Regulated eIF-2alpha Kinase,Hemin Controlled Repressor,Hemin-Controlled Translational Repressor,P68 Protein Kinase,Self-Phosphorylating Protein Kinase,TIK Kinase,dsRNA-Activated Inhibitor,eIF-2alpha Kinase,eRF, eIF-2 Recycling Factor,p65 Kinase,Controlled Repressor, Heme,Controlled Repressor, Hemin,DSRNA Dep Protein Kinase,Double Stranded RNA Dependent eIF 2 alpha Protein Kinase,Heme Controlled Inhibitor,Heme Controlled Translational Repressor,Heme Regulated eIF 2alpha Kinase,Hemin Controlled Translational Repressor,Inhibitor, Heme-Controlled,Inhibitor, dsRNA-Activated,Kinase PKR, Protein,Kinase, DAI Protein,Kinase, DSRNA-Dep Protein,Kinase, Heme-Regulated eIF-2alpha,Kinase, P68 Protein,Kinase, RNA-Dependent Protein,Kinase, Self-Phosphorylating Protein,Kinase, TIK,Kinase, eIF-2,Kinase, eIF-2alpha,Kinase, p65,Kinase, p68,PKR, Protein Kinase,Protein Kinase, DAI,Protein Kinase, DSRNA-Dep,Protein Kinase, P68,Protein Kinase, RNA-Dependent,Protein Kinase, Self-Phosphorylating,RNA Dependent Protein Kinase,Repressor, Heme Controlled,Repressor, Heme-Controlled Translational,Repressor, Hemin Controlled,Repressor, Hemin-Controlled Translational,Self Phosphorylating Protein Kinase,Translational Repressor, Heme-Controlled,Translational Repressor, Hemin-Controlled,dsRNA Activated Inhibitor,eIF 2 Kinase,eIF 2alpha Kinase,eIF-2alpha Kinase, Heme-Regulated,eRF, eIF 2 Recycling Factor
D020449 Repetitive Sequences, Amino Acid A sequential pattern of amino acids occurring more than once in the same protein sequence. There often is some sequence variation between the repeated segments. Many PROTEIN DOMAINS are constituted from repeats. Amino Acid Repeat Sequence,Amino Acid Repetitive Seq

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