Alternative splice variants of the human PKR protein kinase possessing different 5'-untranslated regions: expression in untreated and interferon-treated cells and translational activity.
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.
Kawakubo
K
K
Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA.
Kuhen
K L
KL
Vessey
J W
JW
George
C X
CX
Samuel
C E
CE
D020121:5' Untranslated Regions / Q000235:genetics*; D017398:Alternative Splicing; D000650:Amnion / Q000166:cytology / Q000201:enzymology; D001483:Base Sequence; D002460:Cell Line; D005091:Exons; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015723:Gene Library; D017930:Genes, Reporter; D014644:Genetic Variation; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology*; D007438:Introns; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy; D014176:Protein Biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D019892:eIF-2 Kinase / Q000096:biosynthesis / Q000235:genetics*
D020121:5' Untranslated Regions; D016898:Interferon-alpha; D020319:Oligodeoxyribonucleotides, Antisense; D019892:eIF-2 Kinase