DNA Binding by the ETS-domain Transcription Factor PEA3 Is Regulated by Intramolecular and Intermolecular Protein·Protein Interactions

The cytokine transforming growth factor ␤ (TGF-␤) plays an important role in preventing tumor formation by blocking cell cycle progression. Accordingly, many cancers demonstrate mutations in TGF-␤ signaling components or enhanced expression of inhibitors of the TGF-␤ pathway such as Smad7. In this report we show that the oncoprotein HER2/Neu is able to collaborate with the ETS transcription factor ER81 to activate Smad7 transcription in breast, endometrial, and ovarian cancer cell lines. ER81 binds to two ETS sites within the Smad7 promoter, and mutation of one of these ETS sites greatly decreases Smad7 induction by HER2/Neu and ER81. Furthermore, we show that Smad7 activation involves the processing of signals from HER2/Neu to ER81 via the ERK mitogen-activated protein kinase pathway. Thus, we have uncovered a novel mechanism by which oncogenic HER2/Neu, in collaboration with ER81, can induce carcinogenesis through Smad7 upregulation. Moreover, we show that TAK1, a TGF-␤-activated protein kinase, stimulates ER81 via the p38 mitogen-activated protein kinase pathway and thereby induces the Smad7 promoter. This suggests that attenuation of TGF-␤ signaling by activating Smad7 transcription may proceed not only through TGF-␤ receptorregulated Smad proteins but also through an independent pathway involving ER81 and TAK1.

Section: Smad7 Activation By Her2/neu Tak1 and Er81mentioning

confidence: 54%

HER2/Neu- and TAK1-mediated Up-regulation of the Transforming Growth Factor β Inhibitor Smad7 via the ETS Protein ER81

Dowdy¹,

Mariani²,

Janknecht

2003

“…Foxa2 has been proposed to act by remodeling chromatin and to functionally interact with multiple factors (26, 29 -32). Indeed, interactions between cell-specific factors and other regulators are believed to underlie tissue-specific control by the ubiquitous USF proteins (33)(34)(35)(36)(37)(38). Our overexpression and knockdown data indicate that Foxa2 activation of the CT/CGRP 18-bp enhancer requires the adjacent HLH site that is bound by a USF-1 and -2 heterodimer.…”

Section: Foxa2 and Usf Activation Of Ct/cgrpmentioning

confidence: 73%

Regulation of the Cell-specific Calcitonin/Calcitonin Gene-related Peptide Enhancer by USF and the Foxa2 Forkhead Protein

Viney

Schmidt

Gierasch

et al. 2004

An 18-bp enhancer controls cell-specific expression of the calcitonin/calcitonin gene-related peptide gene. The enhancer is bound by a heterodimer of the bHLH-Zip protein USF-1 and -2 and a cell-specific factor from thyroid C cell lines. In this report we have identified the cell-specific factor as the forkhead protein Foxa2 (previously HNF-3␤). Binding of Foxa2 to the 18-bp enhancer was demonstrated using electrophoretic mobility shift assays. The cell-specific DNA-protein complex was selectively competed by a series of Foxa2 DNA binding sites, and the addition of Foxa2 antiserum supershifted the complex. Likewise, a complex similar to that seen with extracts from thyroid C cell lines was generated using an extract from heterologous cells expressing recombinant The calcitonin/calcitonin gene-related peptide (CT 1 /CGRP) gene expresses the hormone CT in thyroid C cells and the neuropeptide CGRP in neurons. CT is a therapeutically useful modulator of bone metabolism and calcium homeostasis (1), but it may also play additional roles based on the recent unexpected finding of increased bone mass in CT/CGRP and CT receptor knock-out mice (2-4). CGRP is an alternative splicing product from the CT/CGRP gene (5) that is now appreciated to be a member of a gene family of multifunctional neuropeptides that act on related receptors (6 -8). Most notably, CGRP is the most potent peptide dilator known (9, 10), and abnormal levels of CGRP have been implicated in neurovascular and cardiovascular disorders (7,(11)(12)(13). Importantly, CGRP antagonists have recently been reported to be an effective treatment for migraine (14).Regulation of CGRP expression in response to extracellular stimuli is controlled exclusively at the transcriptional level. Studies on both the human and rat CT/CGRP gene have identified a cell-specific enhancer containing helix-loop-helix (HLH) motifs ϳ1 kb upstream of the transcription start site (15-19). We have shown that an 18-bp element with a single HLH site and a flanking octamer-like motif is both sufficient and necessary for cell-specific enhancer activity (18, 19). Using nuclear extracts prepared from the neuronal-like CA77 thyroid C cell line, bHLH-Zip proteins USF-1 and -2 were shown to bind the enhancer in vitro (19). Although Oct1 can bind the A/T-rich half of the flanking site, Oct1 cannot transactivate the enhancer (18). Instead, a cell-specific protein referred to as OB2 was shown to bind an adjacent 8-bp site that partially overlaps the HLH site (19). OB2 was identified as an ϳ68-kDa protein by UV-cross-linking and is present in human and rat thyroid C cell lines but not in cell lines that do not express the CT/CGRP gene (19).In this study have shown that OB2 is the forkhead protein Foxa2, formerly called HNF-3␤. We demonstrate that Foxa2 is able to bind and activate the CT/CGRP enhancer in heterologous cells. Importantly, this transactivation requires the adjacent HLH site and is increased upon co-expression of USF. The combinatorial role of Foxa2 and USF was further demonstrated by short...

“…Additionally, DNA binding of the maize chromosomal HMGB family can be regulated by phosphorylation of the acidic tail, indicating that acidic autoinhibitory regions can be regulated through multiple mechanisms (12). Other examples for such a model of transcription factor cooperation have also been found during the study of the autoinhibitory domains of Ets-1 and PEA3, which are neutralized upon interaction with the transcription factors AML1 and USF-1, respectively, thus enhancing DNA binding (9,43). Similarly, the transcription factor LEF-1 contains an autoinhibitory domain, which is neutralized upon binding of the coactivator ␤-catenin, resulting in enhanced DNA binding (44).…”

Section: Function Of Sox Proteins Is Highly Dependent On Theirmentioning

confidence: 93%

Identification of Novel Domains within Sox-2 and Sox-11 Involved in Autoinhibition of DNA Binding and Partnership Specificity

Wiebe

Nowling

Rizzino

2003

Sox transcription factors play key regulatory roles throughout development, binding DNA through a consensus (A/T)(A/T)CAA(A/T)G sequence. Although many different Sox proteins bind to this sequence, it has been observed that gene regulatory elements are commonly responsive to only a small subset of the entire family, implying that regulatory mechanisms exist to permit selective DNA binding and/or transactivation by Sox family members. To identify and explore the mechanisms modulating gene activation by Sox proteins further, we compared the function of Sox-2 and Sox-11. This led to the discovery that Sox proteins are regulated differentially at multiple levels, including transactivation, protein partnerships with Pit-Oct-Unc (POU) transcription factors, and DNA binding autoregulation. Specifically, we determined that Sox-11 activates transcription more strongly than Sox-2 and that the transactivation domain of Sox-11 is primarily responsible for this capability. Additionally, we demonstrate that the Sox-11 DNA binding domain is responsible for selective cooperation with the POU factor Brn-2. This requirement cannot be replaced by the DNA binding domain of Sox-2, indicating that the DNA binding domain of Sox proteins is critical for Sox-POU partnerships. Interestingly, we have also determined that a conserved domain of Sox-11 has the novel capability of autoinhibiting its ability to bind DNA in vitro and to activate gene expression in vivo. Our findings suggest that the autoinhibitory domain can repress promiscuous binding of Sox-11 to DNA and plays an important role in regulating the recruitment of Sox-11 to specific genes.