Ribosome targeting of PKR is mediated by two double-stranded RNA- binding domains and facilitates in vivo phosphorylation of eukaryotic initiation factor-2

Shuhao Zhu, Patrick R. Romano, Ronald C. Wek

Research output: Contribution to journalArticle

69 Scopus citations

Abstract

Protein kinase PKR is activated in mammalian cells during viral infection, leading to phosphorylation of the α subunit of eukaryotic initiation factor-2 (eIF-2α) and inhibition of protein synthesis. This antiviral response is thought to be mediated by association of double- stranded RNA (ds-RNA), a by-product of viral replication, with two ds-RNA- binding domains (DRBDs) located in the amino terminus of PKR. Recent studies have observed that expression of mammalian PKR in yeast leads to a slow growth phenotype due to hyperphosphorylation of eIF-2α. In this report, we observed that while DRBD sequences are required for PKR to function in the yeast model system, these sequences are not required for in vitro phosphorylation of eIF-2α. To explain this apparent contradiction, we proposed that these sequences are required to target the kinase to the translation machinery. Using sucrose gradient sedimentation, we found that wild-type PKR was associated with ribosomes, specifically with 40 S particles. Deletions or residue substitutions in the DRBD sequences blocked kinase interaction with ribosomes. These results indicate that in addition to mediating ds-RNA control of PKR, the DRBD sequences facilitate PKR association with ribosomes. Targeting to ribosomes may enhance in vivo phosphorylation of eIF-2α, by providing PKR access to its substrate.

Original languageEnglish (US)
Pages (from-to)14434-14441
Number of pages8
JournalJournal of Biological Chemistry
Volume272
Issue number22
DOIs
StatePublished - May 30 1997

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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