Journal
JOURNAL OF IMMUNOLOGY
Volume 177, Issue 1, Pages 315-321Publisher
AMER ASSOC IMMUNOLOGISTS
DOI: 10.4049/jimmunol.177.1.315
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Funding
- NIAID NIH HHS [AI 56152] Funding Source: Medline
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We have shown previously that IFN-gamma and one of its receptor subunits, IFNGR1, are translocated to the nucleus, together with STAT1 alpha as one macromolecular complex, via the classical importin-dependent pathway. In this study, we have identified the nuclear targets of IFN-gamma and IFNGR1. By chromatin immunoprecipitation followed by PCR, IFN-gamma, its receptor subunit IFNGR1, and STAT1 alpha were found to be associated with the IFN-gamma-activated sequence (GAS) in the promoter of two of the genes stimulated by IFN-gamma. Immunoprecipitated chromatin also showed the association of the IFN-gamma, IFNGR1, and STAT1 alpha on the same DNA sequence. Examination of nuclear extracts from WISH cells treated with IFN-gamma revealed the specific binding of IFN-gamma, IFNGR1, and STAT1 alpha to biotinylated GAS nucleotide sequence. Association of IFN-gamma, IFNGR1, and STAT1 alpha with the GAS promoter was also demonstrated by EMSA. Transfection with a GAS-luciferase gene together with the IFNGR1 and nonsecreted IFN-gamma resulted in enhanced reporter activity. In addition, IFNGR1 fused to the yeast GAL4 DNA binding domain resulted in enhanced transcription from a GAL4 response element, suggesting the presence of a trans activation domain in IFNGR1. Our observations put IFN-gamma and its receptor subunit, IFNGR1, in direct contact with the promoter region of IFN-gamma-activated genes with associated increased activity, thus suggesting a transcriptional/cotranscriptional role for IFN-gamma/IFNGR1 as well as a possible role in determining the specificity of IFN-gamma action.
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