Molecular and Cellular Biology, November 2005, p. 9741-9752, Vol. 25, No. 22
0270-7306/05/$08.00+0 doi:10.1128/MCB.25.22.9741-9752.2005
Interleukin-21 Receptor Gene Induction in Human T Cells Is Mediated by T-Cell Receptor-Induced Sp1 Activity
Zheng Wu,
Hyoung-Pyo Kim,
Hai-Hui Xue,
Hong Liu,
Keji Zhao, and
Warren J. Leonard*
Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
Received 20 April 2005/
Returned for modification 6 June 2005/
Accepted 25 August 2005
Interleukin-21 (IL-21) plays important roles in regulating the immune response. IL-21 receptor (IL-21R) mRNA is expressed at a low level in human resting T cells but is rapidly induced by mitogenic stimulation. We now investigate the basis for IL21R gene regulation in T cells. We found that the 80 to 20 region critically regulates IL-21R promoter activity and corresponds to a major DNase I-hypersensitive site. Electrophoretic mobility shift assays, DNA affinity chromatography followed by mass spectrometry, and chromatin immunoprecipitation assays revealed that Sp1 binds to this region in vitro and in vivo. Moreover, mutation of the Sp1 motif markedly reduced IL-21R promoter activity, and Sp1 small interfering RNAs effectively diminished IL-21R expression in activated T cells. Interestingly, upon T-cell receptor (TCR) stimulation, T cells increased IL-21R expression and Sp1 protein levels while decreasing Sp1 phosphorylation. Moreover, phosphatase inhibitors that increased phosphorylation of Sp1 diminished IL-21R transcription. These data indicate that TCR-induced IL-21R expression is driven by TCR-mediated augmentation of Sp1 protein levels and may partly depend on the dephosphorylation of Sp1.
* Corresponding author. Mailing address: National Institutes of Health, Building 10, Room 7N252, Bethesda, MD 20892-1674. Phone: (301) 496-0098. Fax: (301) 402-0971. E-mail: wjl{at}helix.nih.gov.
Molecular and Cellular Biology, November 2005, p. 9741-9752, Vol. 25, No. 22
0022-538X/05/$08.00+0 doi:10.1128/MCB.25.22.9741-9752.2005
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