Dominant negative function by an alternatively spliced form of the interferon-inducible protein kinase PKR.
The double-stranded RNA (dsRNA)-activated protein kinase PKR (protein kinase dsRNA-dependent) plays an important role in the regulation of protein synthesis by phosphorylating the alpha-subunit of eukaryotic initiation factor 2. Through this activity, PKR is thought to mediate the antiviral and antiproliferative actions of interferon. Here, we show that the human T cell leukemia Jurkat cells express an alternatively spliced form of PKR with a deletion of exon 7 (PKRDeltaE7), resulting in a truncated protein that retains the two dsRNA-binding motifs. PKRDeltaE7 exhibits a dominant negative function by inhibiting both PKR autophosphorylation and eukaryotic initiation factor 2 alpha-subunit phosphorylation in vitro and in vivo. Reverse transcriptase-polymerase chain reaction assays showed that PKRDeltaE7 is expressed in a broad range of human tissues at variable levels. Interestingly, expression of PKRDeltaE7 is higher in Jurkat cells than in normal peripheral blood mononuclear cells, raising the possibility of a role in cell proliferation and/or transformation. Thus, expression of alternatively spliced forms of PKR may represent a novel mechanism of PKR autoregulation with important implications in the control of cell proliferation.
Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, Montréal, Québec H3T 1E2, Canada.
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D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D002455:Cell Division; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D005091:Exons; D005347:Fibroblasts / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D005799:Genes, Dominant; D017930:Genes, Reporter; D005947:Glucose / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007372:Interferons / Q000378:metabolism*; D019169:Jurkat Cells; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014018:Tissue Distribution; D014162:Transfection; D014616:Vaccinia virus / Q000235:genetics; D019892:eIF-2 Kinase / Q000235:genetics* / Q000378:metabolism*
D018076:DNA, Complementary; D016601:RNA-Binding Proteins; D010768:Phosphoserine; D012313:RNA; D007372:Interferons; D019892:eIF-2 Kinase; D005947:Glucose; D005690:Galactose