Leader Protein of Encephalomyocarditis Virus Binds Zinc, Is Phosphorylated during Viral Infection, and Affects the Efficiency of Genome Translation
| Autor: | Ann C. Palmenberg, Johnathan Dillman, Michael J. Riddle, Marchel Hill, Cheryl M.T. Dvorak, Andrew Pranter, Michael Deibel, David J. Hall |
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| Rok vydání: | 2001 |
| Předmět: |
Picornavirus
viruses Amino Acid Motifs Molecular Sequence Data Genome Viral Virus Mice Viral Proteins 03 medical and health sciences Virology Protein biosynthesis Animals Humans Amino Acid Sequence Translation factor Encephalomyocarditis virus Phosphorylation Peptide sequence Polyproteins 030304 developmental biology Recombination Genetic 0303 health sciences Aphthovirus Cell-Free System biology 030302 biochemistry & molecular biology RNA biology.organism_classification Molecular biology Zinc Cardiovirus Protein Biosynthesis HeLa Cells |
| Zdroj: | Virology. 290:261-271 |
| ISSN: | 0042-6822 |
| Popis: | Encephalomyocarditis virus (EMCV) is the prototype member of the cardiovirus genus of picornaviruses. For cardioviruses and the related aphthoviruses, the first protein segment translated from the plus-strand RNA genome is the Leader protein. The aphthovirus Leader (173-201 amino acids) is an autocatalytic papain-like protease that cleaves translation factor eIF-4G to shut off cap-dependent host protein synthesis during infection. The less characterized cardioviral Leader is a shorter protein (67-76 amino acids) and does not contain recognizable proteolytic motifs. Instead, these Leaders have sequences consistent with N-terminal zinc-binding motifs, centrally located tyrosine kinase phosphorylation sites, and C-terminal, acid-rich domains. Deletion mutations, removing the zinc motif, the acid domain, or both domains, were engineered into EMCV cDNAs. In all cases, the mutations gave rise to viable viruses, but the plaque phenotypes in HeLa cells were significantly smaller than for wild-type virus. RNA transcripts containing the Leader deletions had reduced capacity to direct protein synthesis in cell-free extracts and the products with deletions in the acid-rich domains were less effective substrates at the L/P1 site, for viral proteinase 3Cpro. Recombinant EMCV Leader (rL) was expressed in bacteria and purified to homogeneity. This protein bound zinc stoichiometrically, whereas protein with a deletion in the zinc motif was inactive. Polyclonal mouse sera, raised against rL, immunoprecipitated Leader-containing precursors from infected HeLa cell extracts, but did not detect significant pools of the mature Leader. However, additional reactions with antiphosphotyrosine antibodies show that the mature Leader, but not its precursors, is phosphorylated during viral infection. The data suggest the natural Leader may play a role in regulation of viral genome translation, perhaps through a triggering phosphorylation event. |
| Databáze: | OpenAIRE |
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