Interferon gamma-induced transcription of the high-affinity Fc receptor for IgG requires assembly of a complex that includes the 91-kDa subunit of transcription factor ISGF3.

Abstract

A 39-nt DNA sequence, the interferon y (IFN-y) response region (GRR), is necessary for the IFN-yinduced transcription of the high-affinity Fc receptor for IgG (FcyRI) and sufficient for the IFN-r-induced transcription of transfected plasmids. By using extracts from IFN--treated cells, three protein complexes will assemble in vitro on a 9-nt core region in the 3' domain of the GRR. The sequence of this core resembles the IFN-y-activated sequence (GAS) described for the GBP gene. Mutations in this GAS core region prevent complex assembly and result in the loss of IFN-y induction of reporter constructs containing the mutation. In addition to the GAS core region, a 5' region of the GRR is necessary for optimal IFN-y induction and for formation of one of the (refs. 8, 9, 22, 24 and K. D. Khan, K.S., G. Lindwall, S. E. Maher, J.E.D., and A. L. M. Bothwell, unpublished results). Since the GBP gene is induced by both IFN-y and IFN-a, interaction of the 91-kDa protein with the GAS may provide a common pathway for transcriptional activation by IFN-a and IFN-y.In previous work we have focused (25) on the mechanism by which IFN-y specifically induces transcription of target genes. FcyRI, in contrast to the GBP, is induced only by IFN-'y. A 39-nt sequence, called the IFN-y response region (GRR), has been identified in the promoter of this gene that is both necessary and sufficient for transcriptional activation by IFN-y (25) and does not respond to IFN-a (unpublished data). These transfection results correlate with the transcriptional induction of FcyRI in macrophages in response to IFN-y that is robust, rapid, and cycloheximide-resistant. In contrast, IFN-a treatment of macrophages results in insignificant FcyRI transcriptional induction (ref. 3 and unpublished observation). Induction of FcyRI accounts for some of the responses attributed to the activated macrophage, such as increased phagocytosis and enhanced antibody-dependent cellular cytotoxicity (26).We now present evidence for the rapid induction of specific protein complexes that assemble on the GRR in IFN--stimulated cells. Mutations that prevent assembly of these complexes in vitro also prevent response to IFN-y induction in transfection experiments with reporter constructs. These complexes interact with a 9-nt core sequence in the GRR that is homologous to the GAS sites found in other IFN-y-induced genes. The 91-kDa DNA binding protein that interacts with the GBP promoter also binds to the GRR of the FcyRI gene. Surprisingly, IFN-a also induces the formation of similar complexes on the GRR yet fails to induce significant transcriptional activation of FcyRI or the GRR. We have begun to reconcile these results by the identification of a second domain within the 5' region of the GRR that is required for optimal IFN-y 4314The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Enhancement of Antiproliferative Activity of Gamma Interferon by the Specific Inhibition of Tyrosine Dephosphorylation of Stat1

“…Gel mobility shift analysis was performed as previously described (24). The Stat1 binding site from the promoter of the human Fc␥RI receptor was used as the probe (32,38).…”

Cytokine regulation of expression of class I MHC antigens

“…In case of IFN-γ, only the 91 kDa (Stat 1a) is phosphorylated (Shuai et al 1992, Pearse et al, 1993. Phosphorylated Stat1 dimerizes, translocates to the nucleus and binds the IFN-γ activation sites (GAS) in the promoter regions of IFN responsive genes, like class I MHC gene.…”

Nuclear integration of JAK/STAT and Ras/AP-1 signaling by CBP and p300

“…Transcriptional responses to IFN-␥ require STAT1␣, which becomes tyrosine-phosphorylated, dimerizes, and binds to specific gamma activated sites (GASs) in target genes (2)(3)(4)(5). To investigate the mechanisms by which IFN-␥ also exerts antagonistic effects on gene expression, we have used the scavenger receptor A (SR-A) gene as a model.…”