Analysis of SOCS-3 Promoter Responses to Interferon γ

Abstract

SOCS-3 (suppressor of cytokine signaling 3) is an intracellular protein that is selectively and rapidly induced by appropriate agonists and that modulates responses of immune cells to cytokines by interfering with the Janus kinase/signal transducer and activator of transcription (Jak/STAT) pathway. On the basis of the observations that interferon ␥ (IFN␥) up-regulates SOCS-3 gene and protein expression in primary mouse macrophages, J774 macrophage cell line and embryonal fibroblasts, we investigated which sequences of the 5 SOCS-3 gene are responsive to IFN␥. By promoter deletion analysis we identified a functional IFN␥-responsive element, located at nucleotides ؊72/؊64 upstream from the transcription initiation, whose presence and integrity is necessary to ensure responsiveness to IFN␥. This element contains a STAT consensus binding sequence (SOCS-3/STAT-binding element (SBE)) whose specific mutation totally abolished the responsiveness to IFN␥. In contrast, discrete deletion of other 5 regions of the SOCS-3 promoter did not substantially modify the inducibility by IFN␥. Electromobility shift assay analyses revealed that IFN␥ promotes specific DNA binding activities to an oligonucleotide probe containing the SOCS-3/SBE sequence. Even though IFN␥ triggered tyrosine phosphorylation of both STAT1 and STAT3 in macrophages and J774 cells, only STAT1 was appropriately activated and thus found to specifically bind to the SOCS-3/SBE oligonucleotide probe. Accordingly, IFN␥-induced SOCS-3 protein expression was not impaired in STAT3-deficient embryonal fibroblasts. Taken together, these results demonstrate that the induction of SOCS-3 by IFN␥ depends upon the presence of a STAT-binding element in the SOCS-3 promoter that is specifically activated by STAT1.

IL-6 signaling via the STAT3/SOCS3 pathway: Functional Analysis of the Conserved STAT3 N-domain

“…Recent studies have demonstrated that Socs3 gene expression can be stimulated by a STAT1-dependent pathway in response to IFNγ (54). Moreover, STAT1 and STAT3 were found to have interchangeable functions in IFNγ-dependent regulation of SOCS3 (57).…”

Pyrrolidine Dithiocarbamate Inhibits Interleukin-6 Signaling through Impaired STAT3 Activation and Association with Transcriptional Coactivators in Hepatocytes

“…Suppressor of cytokine signaling (SOCS)-3 is induced rapidly by activated STATs via the presence of a STAT binding element in its promoter (34,35). To investigate the role of PDTC on the expression of SOCS3 protein, HepG2 cells were treated with the drug for 2 h before the addition of IL-6 for 90 min, and protein lysates were subjected to immunoblot analysis.…”

Gemfibrozil, a Lipid-lowering Drug, Induces Suppressor of Cytokine Signaling 3 in Glial Cells

“…Now that we have established the PI3K/AKT pathway to be critical for the up-regulation of SOCS3, we tried to find out the transcription factor involved in this pathway. The Socs-3 promoter contains numerous potential regulatory elements (45,46). A careful analysis of its promoter sites revealed two potential binding sites for KLF4 and multiple binding sites for AP-1 and NF-B.…”