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Alternative splice variants of the human PKR protein kinase possessing different 5'-untranslated regions: expression in untreated and interferon-treated cells and translational activity.

Authors
  • 1
  • 1 Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA.
Type
Published Article
Journal
Virology
Publication Date
Volume
264
Issue
1
Pages
106–114
Identifiers
PMID: 10544135
Source
Medline
License
Unknown

Abstract

The double-stranded RNA-dependent protein kinase PKR is an interferon-inducible enzyme that possesses antiviral and antiproliferative activities. We examined expression of PKR transcripts in human placenta tissue and cultured human amnion U cells. Alternative exon 2 structures were identified and characterized that possess different functional activities. Cloning and sequence analyses of 5'-RACE cDNAs from human placenta established a linkage between exon 1 and three alternative exon 2 structures that constitute, together with part of exon 3, the 5'-untranslated region of the PKR mRNA. The alternative splice variants of exon 2 were designated Ex2alpha (83 nucleotides), Ex2beta (167 nucleotides), and Ex2gamma (401 nucleotides). All three exon 2 variants were present in placenta tissue. However, only the Ex2alpha and Ex2beta forms were detectable in the amnion U cell line. Nuclease protection analysis revealed that the Ex2beta form was slightly more abundant than the Ex2alpha form, in both placenta tissue and U cells. Interferon treatment of U cells increased the level of both Ex2alpha and Ex2beta RNA by approximately 5-fold. The translational activities, measured in a luciferase reporter assay, of RNA transcripts possessing the Ex2alpha and Ex2beta forms of the PKR 5'-UTR were comparable to each other and more efficient than those with the Ex2gamma form.

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