title: A new double-stranded RNA-binding protein that interacts with PKR.
abstract: We have identified a 74 kDa double-stranded (ds)RNA-binding protein that shares extensive homology with the mouse spermatid perinuclear RNA-binding (Spnr) protein. p74 contains two dsRNA-binding motifs (dsRBMs) that are essential for preferential binding to dsRNA. Previously, dsRNA-binding proteins were shown to undergo homo- and heterodimerization, raising the possibility that regulation of activity could be controlled by interactions between different family members. Homodimerization is required to activate the dsRNA-dependent protein kinase PKR, whereas hetero-dimerization between PKR and other dsRNA-binding proteins can inhibit kinase activity. We have found that p74 also interacts with PKR, both the wild-type enzyme and a catalytically defective mutant (K296R). While co-expression of p74 and wild-type PKR in the yeast Saccharomyces cerevisiae did not alter PKR activity, co-expression of p74 and the catalytically defective K296R mutant surprisingly resulted in abnormal morphology and cell death in transformants that maintained a high level of p74 expression. These transformants could be rescued by overexpression of the alpha-subunit of wild-type eukaryotic translation initiation factor 2 (eIF2alpha), one of the known substrates for PKR. We hypothesize that competing heterodimers between p74-K296R PKR and eIF2alpha-K296R PKR may control cell growth such that stabilization of the p74-K296R PKR heterodimer induces abnormal morphology and cell death.
authors.affiliation: Department of Molecular Biology, Box 1820, Station B, Vanderbilt University, Nashville, TN 37235, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Coolidge
authors.forename: J G
authors.initials: JG
authors.lastname: Patton
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D019281:Dimerization; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism; D005804:Genes, Lethal / Q000235:genetics; D016153:Genes, Suppressor / Q000235:genetics; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000737:chemistry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation / Q000235:genetics; D011119:Polynucleotides / Q000378:metabolism; D011233:Precipitin Tests; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism*
chemical_list: D015852:Eukaryotic Initiation Factor-2; D008869:Microtubule-Associated Proteins; D011119:Polynucleotides; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C490552:Strbp protein, rat; D019892:eIF-2 Kinase