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Eleanor N. Fish - One of the best experts on this subject based on the ideXlab platform.
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The interferon-inducible Stat2:Stat1 heterodimer preferentially binds in vitro to a consensus element found in the promoters of a subset of interferon-stimulated genes.
Journal of Interferon and Cytokine Research, 2001Co-Authors: Julien Ghislain, Melody Nguyen, Thomas Wong, Eleanor N. FishAbstract:Regulated expression of type I interferon (IFN)-stimulated genes (ISG) requires the binding of the signal transducer and activator of transcription (Stat) complexes to enhancer elements located in the ISG promoters. These enhancer elements include the IFN-stimulated response element (ISRE) and the palindromic IFN-γ activation site (GAS) element. Regulated expression of ISRE containing ISG depends on IFN-stimulated gene factor 3 (ISGF3), a heterodimer involving Stat1 and Stat2 in association with a DNA-binding adapter protein, p48/IFN regulatory factor-9 (IRF-9). Several GAS binding Stat complexes involving Stat1, STAT3, Stat4, and Stat5 have been described, but their contribution to GAS-dependent ISG expression remains to be established. We and others previously identified an IFN-α-inducible Stat2:1 heterodimer that exhibits binding to the GAS element of the IRF-1 gene. These previous studies raise the possibility that Stat2:1 may participate in the transcriptional activation of the subset of ISG containi...
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The interferon-inducible Stat2:Stat1 heterodimer preferentially binds in vitro to a consensus element found in the promoters of a subset of interferon-stimulated genes.
Journal of Interferon and Cytokine Research, 2001Co-Authors: Julien Ghislain, Melody Nguyen, Thomas Wong, Eleanor N. FishAbstract:Regulated expression of type I interferon (IFN)-stimulated genes (ISG) requires the binding of the signal transducer and activator of transcription (Stat) complexes to enhancer elements located in the ISG promoters. These enhancer elements include the IFN-stimulated response element (ISRE) and the palindromic IFN-γ activation site (GAS) element. Regulated expression of ISRE containing ISG depends on IFN-stimulated gene factor 3 (ISGF3), a heterodimer involving Stat1 and Stat2 in association with a DNA-binding adapter protein, p48/IFN regulatory factor-9 (IRF-9). Several GAS binding Stat complexes involving Stat1, STAT3, Stat4, and Stat5 have been described, but their contribution to GAS-dependent ISG expression remains to be established. We and others previously identified an IFN-α-inducible Stat2:1 heterodimer that exhibits binding to the GAS element of the IRF-1 gene. These previous studies raise the possibility that Stat2:1 may participate in the transcriptional activation of the subset of ISG containi...
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Application of Genomic DNA Affinity Chromatography Identifies Multiple Interferon-α-regulated Stat2 Complexes
Journal of Biological Chemistry, 1996Co-Authors: Julien J. Ghislain, Eleanor N. FishAbstract:Abstract Interferon-α (IFN-α)-induced signal transduction is mediated by the phosphorylation-activation of the signal transducer and activator of transcription (STAT) proteins Stat1, Stat2, and STAT3. Previous studies have shown that these activated STATs dimerize to form four distinct STAT complexes which translocate to the nucleus and activates transcription by binding to specific promoter elements. The interferon-stimulated gene factor-3 (ISGF3) consists of Stat2 and Stat1 heterodimers in association with a DNA-binding protein, p48, that binds to the interferon stimulated response element. Homo- and heterodimers of Stat1 and STAT3 bind to the palindromic interferon response element (pIRE). In this report we demonstrate the utility of a biochemical procedure that we have developed, based on genomic DNA affinity chromatography, for the identification of IFN-α-induced STAT complexes. Using this approach, we identified ISGF3-independent Stat2-containing STAT complexes. Results from the analysis of Stat2 complexes in the electrophoretic mobility shift assay were consistent with genomic DNA affinity chromatography results and identified a Stat2:1 complex that binds with low affinity to the pIRE of the interferon regulatory factor-1 gene. Immunoprecipitation studies of Stat2 revealed an IFN-α dependent co-precipitation of both Stat1 and STAT3. Taken together, our results suggest that IFN-α activates, in addition to ISGF3, other Stat2-containing STAT complexes, one of which binds to an element related to the interferon regulatory factor-1 pIRE.
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Application of Genomic DNA Affinity Chromatography Identifies Multiple Interferon-α-regulated Stat2 Complexes
Journal of Biological Chemistry, 1996Co-Authors: Julien J. Ghislain, Eleanor N. FishAbstract:Abstract Interferon-α (IFN-α)-induced signal transduction is mediated by the phosphorylation-activation of the signal transducer and activator of transcription (STAT) proteins Stat1, Stat2, and STAT3. Previous studies have shown that these activated STATs dimerize to form four distinct STAT complexes which translocate to the nucleus and activates transcription by binding to specific promoter elements. The interferon-stimulated gene factor-3 (ISGF3) consists of Stat2 and Stat1 heterodimers in association with a DNA-binding protein, p48, that binds to the interferon stimulated response element. Homo- and heterodimers of Stat1 and STAT3 bind to the palindromic interferon response element (pIRE). In this report we demonstrate the utility of a biochemical procedure that we have developed, based on genomic DNA affinity chromatography, for the identification of IFN-α-induced STAT complexes. Using this approach, we identified ISGF3-independent Stat2-containing STAT complexes. Results from the analysis of Stat2 complexes in the electrophoretic mobility shift assay were consistent with genomic DNA affinity chromatography results and identified a Stat2:1 complex that binds with low affinity to the pIRE of the interferon regulatory factor-1 gene. Immunoprecipitation studies of Stat2 revealed an IFN-α dependent co-precipitation of both Stat1 and STAT3. Taken together, our results suggest that IFN-α activates, in addition to ISGF3, other Stat2-containing STAT complexes, one of which binds to an element related to the interferon regulatory factor-1 pIRE.
Curt M Horvath - One of the best experts on this subject based on the ideXlab platform.
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Transcriptional regulation by STAT1 and STAT2 in the interferon JAK-STAT pathway
JAK-STAT, 2013Co-Authors: Nancy Au-yeung, Roli Mandhana, Curt M HorvathAbstract:STAT1 and STAT2 proteins are key mediators of type I and type III interferon (IFN) signaling, and are essential components of the cellular antiviral response and adaptive immunity. They associate with IFN regulatory factor 9 (IRF9) to form a heterotrimeric transcription factor complex known as ISGF3. The regulation of IFN-stimulated gene (ISG) expression has served as a model of JAK-STAT signaling and mammalian transcriptional regulation, but to date has primarily been analyzed at the single gene level. While many aspects of ISGF3-mediated gene regulation are thought to be common features applicable to several ISGs, there are also many reports of distinct cases of non-canonical STAT1 or STAT2 signaling events and distinct patterns of co-regulators that contribute to gene-specific transcription. Recent genome-wide studies have begun to uncover a more complete profile of ISG regulation, moving toward a genome-wide understanding of general mechanisms that underlie gene-specific behaviors.
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A Point Mutation, E95D, in the Mumps Virus V Protein Disengages STAT3 Targeting from STAT1 Targeting
Journal of Virology, 2009Co-Authors: Mamta Puri, W. Paul Duprex, Bertus K. Rima, Ken Lemon, Curt M HorvathAbstract:Mumps virus, like other paramyxoviruses in the Rubulavirus genus, encodes a V protein that can assemble a ubiquitin ligase complex from cellular components, leading to the destruction of cellular signal transducer and activator of transcription (STAT) proteins. While many V proteins target the interferon-activated STAT1 or STAT2 protein, mumps virus V protein is unique in its ability to also target STAT3 for ubiquitin modification and proteasome-mediated degradation. Here we report that a single amino acid substitution in the mumps virus V protein, E95D, results in defective STAT3 targeting while maintaining the ability to target STAT1. Results indicate that the E95D mutation disrupts the ability of the V protein to associate with STAT3. A recombinant mumps virus carrying the E95D mutation in its P and V proteins replicates normally in cultured cells but fails to induce targeting of STAT3. Infection with the recombinant virus results in the differential regulation of a number of cellular genes compared to wild-type mumps virus and increases cell death in infected cells, producing a large-plaque phenotype.
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Composition and assembly of STAT-targeting ubiquitin ligase complexes: paramyxovirus V protein carboxyl terminus is an oligomerization domain.
Journal of Virology, 2005Co-Authors: Christina M. Ulane, Alex Kentsis, Cristian D. Cruz, Jean Patrick Parisien, Kristi L. Schneider, Curt M HorvathAbstract:Transcription regulators STAT1 and STAT2 are key components of the interferon signaling system leading to innate antiviral immunity. The related STAT3 protein is a regulator of interleukin-6-type cytokine signals and can contribute to both cell growth and death important for cancer gene regulation and tumor survival. These three STAT proteins are targeted for proteasome-mediated degradation by RNA viruses in the Rubulavirus genus of the Paramyxoviridae. A single viral protein, the V protein, assembles STAT-specific ubiquitin ligase complexes from cellular components. Simian virus 5 (SV5) targets STAT1, human parainfluenza virus 2 targets STAT2, and mumps virus targets both STAT1 and STAT3. Analysis of the V-dependent degradation complex (VDC) composition and assembly revealed several features contributing to targeting specificity. SV5 and mumps V proteins require STAT2 to recruit the STAT1 target, yet mumps V protein binds STAT3 independent of STAT1 and STAT2. All Rubulavirus V proteins tested require cellular DDB1 to target STATs for degradation but differ in the use of Roc1, which is essential for mumps V STAT3 targeting. Protein interaction analysis reveals that paramyxovirus V proteins can homo- and heterooligomerize and that the conserved cysteine-rich zinc-binding C-terminal domain is necessary and sufficient for oligomerization. Purified SV5 V protein spontaneously assembles into spherical macromolecular particles, and similar particles constitute SV5 and mumps VDC preparations.
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hendra virus v protein inhibits interferon signaling by preventing stat1 and stat2 nuclear accumulation
Journal of Virology, 2003Co-Authors: Jason J. Rodriguez, Lin Fa Wang, Curt M HorvathAbstract:The V protein of the recently emerged paramyxovirus, Nipah virus, has been shown to inhibit interferon (IFN) signal transduction through cytoplasmic sequestration of cellular STAT1 and STAT2 in high-molecular-weight complexes. Here we demonstrate that the closely related Hendra virus V protein also inhibits cellular responses to IFN through binding and cytoplasmic sequestration of both STAT1 and STAT2, but not STAT3. These findings demonstrate a V protein-mediated IFN signal evasion mechanism that is a general property of the known Henipavirus species.
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STAT3 ubiquitylation and degradation by mumps virus suppress cytokine and oncogene signaling.
Journal of Virology, 2003Co-Authors: Christina M. Ulane, Jean Patrick Parisien, Jason J. Rodriguez, Curt M HorvathAbstract:Mumps virus is a common infectious agent of humans, causing parotitis, meningitis, encephalitis, and orchitis. Like other paramyxoviruses in the genus Rubulavirus, mumps virus catalyzes the proteasomal degradation of cellular STAT1 protein, a means for escaping antiviral responses initiated by alpha/beta and gamma interferons. We demonstrate that mumps virus also eliminates cellular STAT3, a protein that mediates transcriptional responses to cytokines, growth factors, nonreceptor tyrosine kinases, and a variety of oncogenic stimuli. STAT1 and STAT3 are independently targeted by a single mumps virus protein, called V, that assembles STAT-directed ubiquitylation complexes from cellular components, including STAT1, STAT2, STAT3, DDB1, and Cullin4A. Consequently, mumps virus V protein prevents responses to interleukin-6 and v-Src signals and can induce apoptosis in STAT3-dependent multiple myeloma cells and transformed murine fibroblasts. These findings demonstrate a unique cytokine and oncogene evasion property of mumps virus that provides a molecular basis for its observed oncolytic properties.
Patrick T. Gunning - One of the best experts on this subject based on the ideXlab platform.
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A STAT inhibitor patent review: progress since 2011
Expert Opinion on Therapeutic Patents, 2015Co-Authors: Ping-shan Lai, David A. Rosa, Ahmed Magdy Ali, Rodolfo F. Gómez-biagi, Daniel P. Ball, Andrew E. Shouksmith, Patrick T. GunningAbstract:Introduction: The clinical utility of effective direct STAT inhibitors, particularly STAT3 and STAT5, for treating cancer and other diseases is well studied and known.Areas covered: This review will highlight the STAT inhibitor patent literature from 2011 to 2015 inclusive. Emphasis will be placed on inhibitors of the STAT3, STAT5a/b, and STAT1 proteins for cancer treatment. The review will, where suitably investigated, describe the mode and the site of inhibition, list indications that were evaluated, and rank the inhibitor’s relative potency among compounds in the same class. The reader will gain an understanding of the diverse set of approaches, used both in academia and industry, to target STAT proteins.Expert opinion: There is still much work to be done to directly target the STAT3 and STAT5 proteins. As yet, there is still no direct STAT3 inhibitor in the clinic. While the SH2 domain remains a popular target for therapeutic intervention, the DNA-binding domain and N-terminal region are now attractin...
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Small molecule STAT5-SH2 domain inhibitors exhibit potent antileukemia activity.
Journal of Medicinal Chemistry, 2012Co-Authors: Brent D. G. Page, Mark D. Minden, Rob C. Laister, Haytham Khoury, Steven Fletcher, Megan Vellozo, Alessia Manzoli, Peibin Yue, James Turkson, Patrick T. GunningAbstract:A growing body of evidence shows that Signal Transducer and Activator of Transcription 5 (STAT5) protein, a key member of the STAT family of signaling proteins, plays a pivotal role in the progression of many human cancers, including acute myeloid leukemia and prostate cancer. Unlike STAT3, where significant medicinal effort has been expended to identify potent direct inhibitors, Stat5 has been poorly investigated as a molecular therapeutic target. Thus, in an effort to identify direct inhibitors of STAT5 protein, we conducted an in vitro screen of a focused library of SH2 domain binding salicylic acid-containing inhibitors (∼150) against STAT5, as well as against STAT3 and STAT1 proteins for SH2 domain selectivity. We herein report the identification of several potent (K(i) 3-fold specificity for STAT5 cf. STAT1 and STAT3) inhibitors, BP-1-107, BP-1-108, SF-1-087, and SF-1-088. Lead agents, evaluated in K562 and MV-4-11 human leukemia cells, showed potent induction of apoptosis (IC(50)'s ∼ 20 μM) which correlated with potent and selective suppression of STAT5 phosphorylation, as well as inhibition of STAT5 target genes cyclin D1, cyclin D2, C-MYC, and MCL-1. Moreover, lead agent BP-1-108 showed negligible cytotoxic effects in normal bone marrow cells not expressing activated STAT5 protein. Inhibitors identified in this study represent some of the most potent direct small molecule, nonphosphorylated inhibitors of STAT5 to date.
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small molecule stat5 sh2 domain inhibitors exhibit potent antileukemia activity
Journal of Medicinal Chemistry, 2012Co-Authors: Brent D. G. Page, Mark D. Minden, Rob C. Laister, Haytham Khoury, Steven Fletcher, Megan Vellozo, Alessia Manzoli, James Turkson, Patrick T. GunningAbstract:A growing body of evidence shows that Signal Transducer and Activator of Transcription 5 (STAT5) protein, a key member of the STAT family of signaling proteins, plays a pivotal role in the progression of many human cancers, including acute myeloid leukemia and prostate cancer. Unlike STAT3, where significant medicinal effort has been expended to identify potent direct inhibitors, Stat5 has been poorly investigated as a molecular therapeutic target. Thus, in an effort to identify direct inhibitors of STAT5 protein, we conducted an in vitro screen of a focused library of SH2 domain binding salicylic acid-containing inhibitors (∼150) against STAT5, as well as against STAT3 and STAT1 proteins for SH2 domain selectivity. We herein report the identification of several potent (Ki 3-fold specificity for STAT5 cf. STAT1 and STAT3) inhibitors, BP-1-107, BP-1-108, SF-1-087, and SF-1-088. Lead agents, evaluated in K562 and MV-4-11 human leukemia cells, showed potent induction of apoptosi...
Julien Ghislain - One of the best experts on this subject based on the ideXlab platform.
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The interferon-inducible Stat2:Stat1 heterodimer preferentially binds in vitro to a consensus element found in the promoters of a subset of interferon-stimulated genes.
Journal of Interferon and Cytokine Research, 2001Co-Authors: Julien Ghislain, Melody Nguyen, Thomas Wong, Eleanor N. FishAbstract:Regulated expression of type I interferon (IFN)-stimulated genes (ISG) requires the binding of the signal transducer and activator of transcription (Stat) complexes to enhancer elements located in the ISG promoters. These enhancer elements include the IFN-stimulated response element (ISRE) and the palindromic IFN-γ activation site (GAS) element. Regulated expression of ISRE containing ISG depends on IFN-stimulated gene factor 3 (ISGF3), a heterodimer involving Stat1 and Stat2 in association with a DNA-binding adapter protein, p48/IFN regulatory factor-9 (IRF-9). Several GAS binding Stat complexes involving Stat1, STAT3, Stat4, and Stat5 have been described, but their contribution to GAS-dependent ISG expression remains to be established. We and others previously identified an IFN-α-inducible Stat2:1 heterodimer that exhibits binding to the GAS element of the IRF-1 gene. These previous studies raise the possibility that Stat2:1 may participate in the transcriptional activation of the subset of ISG containi...
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The interferon-inducible Stat2:Stat1 heterodimer preferentially binds in vitro to a consensus element found in the promoters of a subset of interferon-stimulated genes.
Journal of Interferon and Cytokine Research, 2001Co-Authors: Julien Ghislain, Melody Nguyen, Thomas Wong, Eleanor N. FishAbstract:Regulated expression of type I interferon (IFN)-stimulated genes (ISG) requires the binding of the signal transducer and activator of transcription (Stat) complexes to enhancer elements located in the ISG promoters. These enhancer elements include the IFN-stimulated response element (ISRE) and the palindromic IFN-γ activation site (GAS) element. Regulated expression of ISRE containing ISG depends on IFN-stimulated gene factor 3 (ISGF3), a heterodimer involving Stat1 and Stat2 in association with a DNA-binding adapter protein, p48/IFN regulatory factor-9 (IRF-9). Several GAS binding Stat complexes involving Stat1, STAT3, Stat4, and Stat5 have been described, but their contribution to GAS-dependent ISG expression remains to be established. We and others previously identified an IFN-α-inducible Stat2:1 heterodimer that exhibits binding to the GAS element of the IRF-1 gene. These previous studies raise the possibility that Stat2:1 may participate in the transcriptional activation of the subset of ISG containi...
Kenneth M. Murphy - One of the best experts on this subject based on the ideXlab platform.
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Role of the Stat4 N domain in receptor proximal tyrosine phosphorylation.
Molecular and cellular biology, 2000Co-Authors: Theresa L. Murphy, E. D. Geissal, J. D. Farrar, Kenneth M. MurphyAbstract:The STAT (signal transducers and activators of transcription) family of transcription factors reside as latent cytoplasmic monomers which are phosphorylated on a conserved tyrosine residue in response to ligand-induced receptor activation (5, 15, 38). Following tyrosine phosphorylation, STAT proteins undergo homo- and heterodimerization via reciprocal interactions involving their conserved SH2 domains, followed by STAT dimer nuclear translocation and participation in transcriptional regulation of various cytokine responsive genes. STAT dimers bind the palindromic gamma interferon (IFN-γ)-activated sequence (GAS) TTCNmGAA, where m equals 3 for all STAT proteins except Stat6 (6, 7, 14, 19). STAT-specific binding site preferences have been identified involving both the central nucleotide core and sequences flanking the core palindrome (10, 25, 33, 34). Furthermore, higher-order interactions between STAT dimers, in which a tetrameric complex of two STAT dimers cooperatively binds two adjacent GAS elements, have been described for Stat1, Stat4, and Stat5 (42, 43, 47). It has been suggested that such tetramer formation is facilitated through interactions between the highly conserved N-terminal domain (N domain), facilitating STAT dimer binding to low-affinity, nonconsensus STAT binding sites (47). Other functions for the N domain have also been suggested, including roles in nuclear localization and binding to CREB-binding protein, or p300 (39, 48). The specificity of STAT activation by cytokines is in part mediated by the selective interaction of their SH2 domains with distinct tyrosine-containing motifs located within the cytoplasmic domains of specific cytokine receptors. In addition, each STAT protein has private physiologic functions exerted presumably by selective activation of distinct target genes. One important STAT-dependent biologic function involves T helper differentiation. In particular, Stat4 activation plays a significant role in directing development of T helper type 1 (Th1) T cells from naive CD4+ precursors (16, 18, 41). Control of Th1 differentiation is exerted both by the tissue-restricted expression of Stat4 and by the limited activation of Stat4 by only certain cytokines. Stat4 is activated by interleukin 12 (IL-12) (1, 16), a cytokine which potently induces Th1 development (13, 22) through recruitment to a tyrosine-based motif in the IL-12 receptor β2 (IL-12Rβ2) subunit via the Stat4 SH2 domain (26). IL-12 activates Stat4 in all species examined, and the requirement for Stat4 in Th1 development has been confirmed by targeted deletion of Stat4 in mice (18, 41). IFN-α also activates Stat4 and induces Th1 development in human T cells (1, 32), but not mouse T cells (32, 46). Stat4 activation by IFN-α, however, does not involve direct binding to the cytoplasmic domain of the IFN-α receptor (IFN-αR), but instead occurs through an intermediate step (8). First, IFN-α signaling leads to phosphorylation of a conserved tyrosine in the receptor cytoplasmic domain that acts to recruit Stat2, which is subsequently phosphorylated on a conserved tyrosine 690. Stat2 serves as an adapter that binds the SH2 domains of both Stat1 and Stat4. Stat1 binds to tyrosine 690 of Stat2; however, Stat4 binds to a distinct region of Stat2, specifically to the most carboxy-terminal regions of Stat2. In summary, IL-12 and IFN-α each induce Th1 development and activate Stat4, but the Stat4 SH2 domain interaction differs between these receptor pathways. How Stat4 promotes Th1 development is unclear. Stat4 could directly regulate activity of the IFN-γ gene. Recombinant Stat4 produces a footprint on specific sites within the IFN-γ gene promoter and first intron, sites which are low affinity and nonconsensus. The cooperative interaction of adjacent sites with Stat4 dimers binding as a tetramer via adjacent amino termini was suggested as a mechanism for augmenting IFN-γ gene expression (47), although the requirement for these sites in regulation of the native IFN-γ gene has not been established. Alternately, Stat4 may regulate expression of other signaling molecules or transcription factors that act in Th1 development. For example, Stat4 is required for the Th1-specific expression of the Ets transcription family member ERM (28), although a role for ERM in IFN-γ gene expression has not been demonstrated. In addressing potential Stat4 tetramer interactions for IFN-γ regulation, we became interested in the role of the Stat4 N domain in mediating STAT dimer-dimer interactions. The structure of the STAT N domain was determined from the isolated N domain from Stat4, which was found to naturally pack as a dimer in the crystal (43). In the Stat4 N domain, composed of eight alpha helices which form a hook-like structure, a conserved tryptophan residue, W37, was shown to be engaged in critical internal polar interactions between interacting helices of reciprocal N domain subunits (43). For functional analysis, the role of this tryptophan was evaluated in Stat1 rather than Stat4; however, mutation of this tryptophan prevented tetramer formation of recombinant Stat1 protein and caused the loss of an IFN-γ augmentation of a synthetic promoter composed of multimerized GAS elements. Furthermore, mutation of this conserved tryptophan in Stat5 was recently shown to prevent the ability of Stat5 to undergo tetramer formation on the adjacent STAT sites present in the IL-2Rα chain promoter (17). So far, the role of this tryptophan-mediated N domain dimerization had not been evaluated for Stat4 nor evaluated in a system where native physiologic responses to Stat4 activation could be observed. To this end, we have carried out a mutational analysis of the Stat4 N domain for IFN-α- and IL-12-induced Stat4 activation using cell lines that lack Stat4 expression and primary T cells derived from Stat4-deficient mice. Surprisingly, our results point to additional roles of the Stat4 N domain beyond mediating tetramer formation on DNA. Our results indicate that the Stat4 N domain also can influence the ability of STAT proteins to undergo successful interactions with cytokine receptor complexes. Importantly, the W37A mutation within the N domain of Stat4 interferes with IFN-α-induced tyrosine phosphorylation of the Stat4 monomer, interrupting Stat4 activation before formation of the Stat4 dimer. This result precludes any conclusions regarding functional tetramer activity based on this mutation for Stat4. Finally, the data suggest that N-domains may be involved in targeting certain STATs to receptors, influencing their suitability as substrates for receptor-dependent kinases.
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Recruitment of Stat4 to the Human Interferon-α/β Receptor Requires Activated Stat2
The Journal of biological chemistry, 2000Co-Authors: J. David Farrar, Theresa L. Murphy, Janice D. Smith, Kenneth M. MurphyAbstract:Abstract Stat4 activation is involved in differentiation of type 1 helper (Th1) T cells. Although Stat4 is activated by interleukin (IL)-12 in both human and murine T cells, Stat4 is activated by interferon (IFN)-α only in human, but not murine, CD4+ T cells. This species-specific difference in cytokine activation of Stat4 underlies critical differences in Th1 development in response to cytokines and is important to the interpretation of murine models of immunopathogenesis. Here, we sought to determine the mechanism of Stat4 recruitment and activation by the human IFN-α receptor. Analysis of phosphopeptide binding analysis suggests that Stat4 does not interact directly with tyrosine-phosphorylated amino acid residues within the cytoplasmic domains of either of the subunits of the IFN-α receptor complex. Expression of murine Stat4 in the Stat1-deficient U3A and the Stat2-deficient U6A cell lines shows that IFN-α-induced Stat4 phosphorylation requires the presence of activated Stat2 but not Stat1. Thus, in contrast to the direct recruitment of Stat4 by the IL-12 receptor, Stat4 activation by the human IFN-α receptor occurs through indirect recruitment by intermediates involving Stat2.
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recruitment of stat4 to the human interferon α β receptor requires activated stat2
Journal of Biological Chemistry, 2000Co-Authors: David J Farrar, Theresa L. Murphy, Janice D. Smith, Kenneth M. MurphyAbstract:Abstract Stat4 activation is involved in differentiation of type 1 helper (Th1) T cells. Although Stat4 is activated by interleukin (IL)-12 in both human and murine T cells, Stat4 is activated by interferon (IFN)-α only in human, but not murine, CD4+ T cells. This species-specific difference in cytokine activation of Stat4 underlies critical differences in Th1 development in response to cytokines and is important to the interpretation of murine models of immunopathogenesis. Here, we sought to determine the mechanism of Stat4 recruitment and activation by the human IFN-α receptor. Analysis of phosphopeptide binding analysis suggests that Stat4 does not interact directly with tyrosine-phosphorylated amino acid residues within the cytoplasmic domains of either of the subunits of the IFN-α receptor complex. Expression of murine Stat4 in the Stat1-deficient U3A and the Stat2-deficient U6A cell lines shows that IFN-α-induced Stat4 phosphorylation requires the presence of activated Stat2 but not Stat1. Thus, in contrast to the direct recruitment of Stat4 by the IL-12 receptor, Stat4 activation by the human IFN-α receptor occurs through indirect recruitment by intermediates involving Stat2.
