Nuclear factor 90 is a substrate and regulator of the eukaryotic initiation factor 2 kinase double-stranded RNA-activated protein kinase.
Nuclear factor 90 (NF90) is a member of an expanding family of double-stranded (ds) RNA-binding proteins thought to be involved in gene expression. Originally identified in complex with nuclear factor 45 (NF45) as a sequence-specific DNA-binding protein, NF90 contains two double stranded RNA-binding motifs (dsRBMs) and interacts with highly structured RNAs as well as the dsRNA-activated protein kinase, PKR. In this report, we characterize the biochemical interactions between these two dsRBM containing proteins. NF90 binds to PKR through two independent mechanisms: an RNA-independent interaction occurs between the N terminus of NF90 and the C-terminal region of PKR, and an RNA-dependent interaction is mediated by the dsRBMs of the two proteins. Co-immunoprecipitation analysis demonstrates that NF90, NF45, and PKR form a complex in both nuclear and cytosolic extracts, and both proteins serve as substrates for PKR in vitro. NF90 is phosphorylated by PKR in its RNA-binding domain, and this reaction is partially blocked by the NF90 N-terminal region. The C-terminal region also inhibits PKR function, probably through competitive binding to dsRNA. A model for NF90-PKR interactions is proposed.
Parker
L M
LM
Department of Biochemistry and Molecular Biology, New Jersey Medical School, University of Medicine and Dentistry, New Jersey, Newark, New Jersey 07103-2714, USA.
Fierro-Monti
I
I
Mathews
M B
MB
D000818:Animals; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D050778:NFATC Transcription Factors; D051903:Nuclear Factor 45 Protein; D050779:Nuclear Factor 90 Proteins; D009687:Nuclear Proteins / Q000378:metabolism; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion; D013379:Substrate Specificity; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019892:eIF-2 Kinase / Q000737:chemistry / Q000378:metabolism*
D004268:DNA-Binding Proteins; C494013:ILF2 protein, human; D050778:NFATC Transcription Factors; D051903:Nuclear Factor 45 Protein; D050779:Nuclear Factor 90 Proteins; D009687:Nuclear Proteins; D012330:RNA, Double-Stranded; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D012313:RNA; D019892:eIF-2 Kinase