Nuclear Factor-90 of Activated T-Cells: A Double-Stranded RNA-Binding Protein and Substrate for the Double-Stranded RNA-Dependent Protein Kinase, PKR
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- 作者：J. O. Langland ; P. N. Kao ; and B. L. Jacobs
- 刊名：Biochemistry
- 出版年：1999
- 出版时间：May 11, 1999
- 年：1999
- 卷：38
- 期：19
- 页码：6361 - 6368
- 全文大小：99K
- 年卷期：v.38,no.19(May 11, 1999)
- ISSN：1520-4995
文摘
NFAT transcription factors play a central role in initiating T-cell activation through the inductionof immediate-early T-cell specific genes including interleukin-2 (IL-2). NFAT transcription factors bindto a sequence in the IL-2 enhancer known as the antigen receptor response element 2 (ARRE-2). Multipleproteins exhibiting ARRE-2 binding activity have been isolated, including a heterodimer from stimulatedT-cell nuclear extracts consisting of Mr = 90 000 (NF90) and Mr = 45 000 (NF45) subunits. The subunitsof this heterodimer have been cloned, and NF90 was found to encode a protein containing two domainsthat are predicted to form motifs capable of binding to double-stranded RNA. Using in vitro translatedpolypeptides, we have demonstrated that NF90 specifically binds to double-stranded RNA. Furthermore,NF90 was phosphorylated in a double-stranded RNA-dependent manner likely by the interferon-induced,double-stranded RNA-dependent protein kinase, PKR. The NF90 protein was found to be expressed notonly in T-cells, but also in nonimmune HeLa cells. In HeLa cells, the protein was almost exclusivelylocalized to the ribosome salt wash fraction of cell lysates.