DOCSLIB.ORG

Smads Bind Directly to the Jun Family of AP-1 Transcription Factors (Smad3͞smad4͞cjun͞junb͞transforming Growth Factor)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Smads Bind Directly to the Jun Family of AP-1 Transcription Factors (Smad3͞smad4͞cjun͞junb͞transforming Growth Factor) Proc. Natl. Acad. Sci. USA Vol. 96, pp. 4844–4849, April 1999 Biochemistry Smads bind directly to the Jun family of AP-1 transcription factors (Smad3ySmad4ycJunyJunBytransforming growth factor) NICOLE T. LIBERATI,MICHAEL B. DATTO,JOSHUA P. FREDERICK,XING SHEN,CAROLYN WONG, ELISSA M. ROUGIER-CHAPMAN, AND XIAO-FAN WANG* Department of Pharmacology and Cancer Biology, Box 3813, Duke University Medical Center, Durham, NC 27708 Communicated by Gordon G. Hammes, Duke University Medical Center, Durham, NC, September 28, 1998 (received for review July 21, 1998) ABSTRACT Smad3 and Smad4 are sequence-specific cyte chemoattractant protein-1 (JEyMCP-1), type I collagen, DNA-binding factors that bind to their consensus DNA- and TGFb1 itself depends on specific AP-1 DNA-binding sites binding sites in response to transforming growth factor b in the promoter regions of these genes (3, 5–10). Furthermore, (TGFb) and activate transcription. Recent evidence impli- TGFb-mediated transcriptional activation of several of these cates Smad3 and Smad4 in the transcriptional activation of genes requires AP-1 proteins (5, 8–10). Intriguingly, the consensus AP-1 DNA-binding sites that do not interact with expression of many AP-1 proteins themselves is induced as an Smads directly. Here, we report that Smad3 and Smad4 can early response to TGFb in a cell type-specific manner (11–14). physically interact with AP-1 family members. In vitro binding It has been demonstrated that this induced expression of studies demonstrate that both Smad3 and Smad4 bind all particular AP-1 family members is involved in TGFb-mediated three Jun family members: JunB, cJun, and JunD. The Smad regulation of subsequent target genes (10). In addition, genetic interacting region of JunB maps to a C-terminal 20-amino studies of TGFb signaling in Drosophila melanogaster reveal a acid sequence that is partially conserved in cJun and JunD. direct overlap between AP-1 and TGFb signaling and suggest We show that Smad3 and Smad4 also associate with an an evolutionarily conserved convergence of these pathways endogenous form of cJun that is rapidly phosphorylated in (15). Together, these studies demonstrate a link between response to TGFb. Providing evidence for the importance of TGFb signaling and AP-1 in the TGFb-regulated expression this interaction between Smad and Jun proteins, we demon- of various genes. The molecular mechanisms responsible for strate that Smad3 is required for the activation of concatamer- the TGFb-mediated transcriptional activation of these genes ized AP-1 sites in a reporter construct that has previously are just beginning to be elucidated. been characterized as unable to bind Smad proteins directly. Insight into the mechanism of TGFb-regulated gene expres- Together, these data suggest that TGFb-mediated transcrip- sion has come about with the discovery of the Smad family of tional activation through AP-1 sites may involve a regulated proteins. The Smads are phosphorylated by the activated type interaction between Smads and AP-1 transcription factors. I receptor in response to ligand (16). Specifically, Smad2 and Smad3 were shown to be inducibly phosphorylated in response Transforming growth factor b (TGFb) is a multipotent cyto- to TGFb (17–19). Smad phosphorylation results in hetero- kine that regulates a variety of cellular activities, such as cell merization of either Smad2 or Smad3 with Smad4 (20–23). proliferation, differentiation, and extracellular matrix (ECM) Smad4-containing heteromers then enter the nucleus where formation. The combined actions of these cellular responses they can activate transcription of specific genes (24, 25). are likely to mediate more global effects of TGFb including its Current research is focused on elucidating the role of Smads role in development, wound healing, immune responses, and in TGFb-induced transcriptional activation. the pathogenesis of cancer (1–3). The identification of genes Through attempts made at understanding the mechanism of transcriptionally regulated by TGFb and the elucidation of the Smad-mediated transcriptional activation, two distinct roles molecular mechanisms responsible for this transcriptional for Smads have emerged: Smads as DNA-binding factors and regulation will help define how TGFb exerts its cellular effects Smads as transcription factor-binding proteins. Several lines of and its role in resulting physiological processes. Although evidence suggest that Smads activate transcription by binding progress has been made in the identification of TGFb target directly to DNA. For instance, transcription of a reporter genes, including the cyclin-dependent kinase inhibitors p21 plasmid containing the concatamerized consensus Smad- and p15 (1, 2) and the ECM component plasminogen activator binding site is induced by TGFb in a Smad4-dependent inhibitor-1 (PAI-1) (3), which has subsequently contributed manner (26). Smad3 and Smad4 were recently shown to form toward our understanding of TGFb-mediated growth inhibi- a complex on similar DNA sequences derived from the PAI-1 tion and ECM deposition, the mechanisms by which TGFb promoter (27). Mutation of these sequences in the PAI-1 controls gene expression remain largely unknown. promoter reduced TGFb responsiveness. Furthermore, Gal4 Numerous studies have characterized the differential ex- fusions with the C-terminal domains of Smad1 and Smad4 pression of specific genes in response to TGFb, revealing a activate transcription from concatamerized Gal4 DNA- common link in the ability of TGFb to regulate many of these binding sites (28). genes through the functions of the AP-1 family of transcription Other evidence suggests that Smads can activate transcrip- factors. This protein family, which includes the Fos and Jun tion by binding to other transcription factors. For example, the proteins, binds a specific DNA sequence and facilitates tran- interaction between Smad2ySmad4 heteromers and the tran- scriptional regulation (4). The ability of TGFb to induce the scription factor FAST-1 is critical for the formation of the expression of several genes, including PAI-1, clusterin, mono- Abbreviations: TGFb, transforming growth factor b; HaCaT, human The publication costs of this article were defrayed in part by page charge keratinocyte cells; JNK, cJun N-terminal kinase; CMV, cytomegalo- virus; GST, glutathione S-transferase; TNT, transcription and trans- payment. This article must therefore be hereby marked ‘‘advertisement’’ in lation. accordance with 18 U.S.C. §1734 solely to indicate this fact. *To whom reprint requests should be addressed. e-mail: PNAS is available online at www.pnas.org. [email protected]. 4844 Downloaded by guest on October 1, 2021 Biochemistry: Liberati et al. Proc. Natl. Acad. Sci. USA 96 (1999) 4845 activin responsive factor (ARF), an activin-inducible DNA- tained 5 mM 3-aminotriazole. Transformants (242) were pos- binding complex in Xenopus (24, 29). Overexpression of the itive for b-galactosidase activity, which was measured by the Smad-binding domain of FAST-1 blocked ARF formation and appearance of blue color on colony filter lifts incubated in the transcriptional induction of an activin-inducible early response presence of 5-bromo-4-chloro-3-indolyl-b-D-galactosidase (X- gene. Together, these data indicate that although Smads bind Gal). Bait dependence for each positive transformant was DNA directly, association with other transcription factors may established similarly. play a crucial role in Smad-mediated transcriptional activation. Binding Studies. Full length JunB in pGEM4 was digested In an attempt to identify transcription factors involved in with BspHI, BssHII, or DraI (NEB). The full length construct Smad-mediated transcriptional activation, we performed a and the digested DNAs were used as templates for in vitro yeast two-hybrid screen using Smad3 as a bait. Two interacting transcription and translation (TNT) with [35S]methionine in cDNAs encoding two different clones of the AP-1 family rabbit reticulocyte lysates (Promega). The TNT–JunB lysates member, JunB, were isolated, indicating that Smads may bind were incubated with an equal amount of bacterially purified to AP-1 members directly. Supporting a direct interaction glutathione S-transferase (GST), or GST-Smad3 or GST- between Smads and AP-1, we show that Smad3 and Smad4 Smad4 (30) in ByP (150 mM NaCly50 mM Tris, pH 7.5y0.1% bind all known members of the Jun family of proteins in vitro. Tweeny1 mM DTT) for 2.5 hours at 4°C. The GST reactions Furthermore, we demonstrate that Smad3 is critical for the were washed three times in TBS (500 mM NaCly25 mM Tris, ability of TGFb to activate AP-1 sites independent of Smad pH 7.5y0.1% Tween-20y1 mM DTT). Samples were resolved DNA binding. These data, therefore, provide insight into a by SDSyPAGE. The gels were treated with 10% sodium possible mechanism by which TGFb activates AP-1-mediated salicylate, dried, and exposed to film. Whole-cell COS lysates transcription through the induction of SmadyAP-1 complex overexpressing each AP-1 member were lysed as described formation. (30) and incubated with the GST fusions as described above. The binding reactions were washed three times with ByP and y MATERIALS AND METHODS separated by SDS PAGE. For endogenous protein interactions, HaCaT cells were Materials. TGFb1 was a generous gift of Amgen Biologicals. treated with 100 pM TGFb1 in DMEMy10% FBS for 15, 30, Human keratinocyte cells (HaCaT) were the generous gift of or 60 min. Cells were then lysed and either whole-cell or P. Baukamp and N. Fusenig. A HaCaT cDNA library in the nuclear extracts were prepared (30, 31). Four hundred fifty mg pACT2 expression vector was the generous gift of Y. Xiong. of each whole-cell lysate was incubated with an equal amount The full length cDNAs for murine Jun family members, FosB, of bacterially purified GST-Smad3 or GST-Smad4 normalized cFos, Fra2, and human Fra1, were the generous gifts of R. for protein by Coomassie blue and for volume of glutathione- Wisdom. Smad3 polyclonal antibody was generated against Sepharose added to each binding reaction.
Load more

Recommended publications
  • Activation of Smad Transcriptional Activity by Protein Inhibitor of Activated STAT3 (PIAS3)
    Activation of Smad transcriptional activity by protein inhibitor of activated STAT3 (PIAS3) Jianyin Long*†‡, Guannan Wang*†‡, Isao Matsuura*†‡, Dongming He*†‡, and Fang Liu*†‡§ *Center for Advanced Biotechnology and Medicine, †Susan Lehman Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, and ‡Cancer Institute of New Jersey, 679 Hoes Lane, Piscataway, NJ 08854 Communicated by Allan H. Conney, Rutgers, The State University of New Jersey, Piscataway, NJ, November 17, 2003 (received for review August 22, 2003) Smad proteins play pivotal roles in mediating the transforming of many transcription factors through distinct mechanisms. growth factor ␤ (TGF-␤) transcriptional responses. We show in this PIAS1 and PIAS3 bind and inhibit STAT1 and STAT3 DNA- report that PIAS3, a member of the protein inhibitor of activated binding activities, respectively (19, 20). PIASx␣ and PIASx␤ STAT (PIAS) family, activates TGF-␤͞Smad transcriptional re- were identified through interactions with the androgen receptor sponses. PIAS3 interacts with Smad proteins, most strongly with and the homeodomain protein Msx2, respectively (21, 22). Smad3. PIAS3 and Smad3 interact with each other at the endog- PIASx␣ and PIASx␤ inhibit IL12-mediated and STAT4- enous protein level in mammalian cells and also in vitro, and the dependent gene activation (23). PIAS1, PIAS3, PIASx␣, and association occurs through the C-terminal domain of Smad3. We PIASx␤ also regulate transcriptional activation by various ste- further show that PIAS3 can interact with the general coactivators roid receptors (21, 24–26). PIASy has been shown to antagonize p300͞CBP, the first evidence that a PIAS protein can associate with the activities of STAT1 (27), androgen receptor (28), p53 (29), p300͞CBP.
    [Show full text]
  • Tgfβ-Regulated Gene Expression by Smads and Sp1/KLF-Like Transcription Factors in Cancer VOLKER ELLENRIEDER
    ANTICANCER RESEARCH 28 : 1531-1540 (2008) Review TGFβ-regulated Gene Expression by Smads and Sp1/KLF-like Transcription Factors in Cancer VOLKER ELLENRIEDER Signal Transduction Laboratory, Internal Medicine, Department of Gastroenterology and Endocrinology, University of Marburg, Marburg, Germany Abstract. Transforming growth factor beta (TGF β) controls complex induces the canonical Smad signaling molecules which vital cellular functions through its ability to regulate gene then translocate into the nucleus to regulate transcription (2). The expression. TGFβ binding to its transmembrane receptor cellular response to TGF β can be extremely variable depending kinases initiates distinct intracellular signalling cascades on the cell type and the activation status of a cell at a given time. including the Smad signalling and transcription factors and also For instance, TGF β induces growth arrest and apoptosis in Smad-independent pathways. In normal epithelial cells, TGF β healthy epithelial cells, whereas it can also promote tumor stimulation induces a cytostatic program which includes the progression through stimulation of cell proliferation and the transcriptional repression of the c-Myc oncogene and the later induction of an epithelial-to-mesenchymal transition of tumor induction of the cell cycle inhibitors p15 INK4b and p21 Cip1 . cells (1, 3). In the last decade it has become clear that both the During carcinogenesis, however, many tumor cells lose their tumor suppressing and the tumor promoting functions of TGF β ability to respond to TGF β with growth inhibition, and instead, are primarily regulated on the level of gene expression through activate genes involved in cell proliferation, invasion and Smad-dependent and -independent mechanisms (1, 2, 4).
    [Show full text]
  • 5956.Full.Pdf
    Cancer Therapy: Preclinical Radiation and Transforming Growth Factor-B Cooperate inTranscriptional Activation of the Profibrotic Plasminogen Activator Inhibitor-1 Gene Jurre Hageman,1Bart J. Eggen,3 Tom Rozema,1, 2 Kevin Damman,1 Harm H. Kampinga,1and Robert P. Coppes1, 2 Abstract Radiation-induced fibrosis is an important side effect in the treatment of cancer. Profibrotic pro- teins, such as plasminogen activator inhibitor-1 (PAI-1), transforming growth factor-h (TGF-h), and tissue type inhibitor of metalloproteinases-1 (Timp-1), are thought to play major roles in the development of fibrosis via the modulation of extracellular matrix integrity.We did a detailed anal- ysis of transcriptional activation of these profibrotic genes by radiation and TGF-h. Irradiation of HepG2 cells led to a high increase in PAI-1mRNA levels and a mild increase in Timp-1mRNA lev- els. In contrast,TGF-h1and Smad7 were not increased. Radiation and TGF-h showed strong co- operative effects in transcription of the PAI-1 gene. The TGF-b1 gene showed a mild cooperative activation, whereas Timp-1and Smad7 were not cooperatively activated by radiation and TGF-h. Analysis using the proximal 800 bp of the human PAI-1promoter revealed a dose-dependent increase of PAI-1levels between 2 and 32 Gy g-rays that was independent of latent TGF-h acti- vation. Subsequent site-directed mutagenesis of the PAI-1promoter revealed that mutation of a p53-binding element abolished radiation-induced PAI-1 transcription. In line with this, PAI-1 was not activated in p53-null Hep3B cells, indicating that p53 underlies the radiation-induced PAI-1activation and the cooperativity with theTGF-h/Smad pathway.
    [Show full text]
  • Sensing Relative Signal in the Tgf-Β/Smad Pathway PNAS PLUS
    Sensing relative signal in the Tgf-β/Smad pathway PNAS PLUS Christopher L. Fricka,1, Clare Yarkaa, Harry Nunnsa, and Lea Goentoroa,1 aDivision of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125 Edited by Arup K. Chakraborty, Massachusetts Institute of Technology, Cambridge, MA, and approved February 3, 2017 (received for review July 12, 2016) How signaling pathways function reliably despite cellular varia- Smad4. In their heteromeric form, the Smad proteins are retained tion remains a question in many systems. In the transforming more strongly in the nucleus through reduced export rate, as well as, growth factor-β (Tgf-β) pathway, exposure to ligand stimulates as proposed recently (11), accelerated import rate. Thus, ligand nuclear localization of Smad proteins, which then regulate target activation leads to a net accumulation of the Smad complex in gene expression. Examining Smad3 dynamics in live reporter cells, the nucleus, where it regulates target genes. we found evidence for fold-change detection. Although the level The Tgf-β pathway is a particularly interesting system for of nuclear Smad3 varied across cells, the fold change in the level of testing for fold-change detection because it is known that the nuclear Smad3 was a more precise outcome of ligand stimulation. expression levels of its components vary considerably from cell to The precision of the fold-change response was observed through- cell. A recent study using proximity ligation assay in fixed cells out the signaling duration and across Tgf-β doses, and significantly revealed that the levels of Smad3/4 and Smad2/4 complexes vary increased the information transduction capacity of the pathway.
    [Show full text]
  • TGF-Β Signaling
    biomolecules Review TGF-β Signaling Kalliopi Tzavlaki and Aristidis Moustakas * Department of Medical Biochemistry and Microbiology, Science for Life Laboratory, Uppsala University, Box 582, SE-751 23 Uppsala, Sweden; [email protected] * Correspondence: [email protected]; Tel.: +46-18-4714732; Fax: +46-18-4714441 Received: 18 February 2020; Accepted: 20 March 2020; Published: 23 March 2020 Abstract: Transforming growth factor-β (TGF-β) represents an evolutionarily conserved family of secreted polypeptide factors that regulate many aspects of physiological embryogenesis and adult tissue homeostasis. The TGF-β family members are also involved in pathophysiological mechanisms that underlie many diseases. Although the family comprises many factors, which exhibit cell type-specific and developmental stage-dependent biological actions, they all signal via conserved signaling pathways. The signaling mechanisms of the TGF-β family are controlled at the extracellular level, where ligand secretion, deposition to the extracellular matrix and activation prior to signaling play important roles. At the plasma membrane level, TGF-βs associate with receptor kinases that mediate phosphorylation-dependent signaling to downstream mediators, mainly the SMAD proteins, and mediate oligomerization-dependent signaling to ubiquitin ligases and intracellular protein kinases. The interplay between SMADs and other signaling proteins mediate regulatory signals that control expression of target genes, RNA processing at multiple levels, mRNA translation and nuclear or cytoplasmic protein regulation. This article emphasizes signaling mechanisms and the importance of biochemical control in executing biological functions by the prototype member of the family, TGF-β. Keywords: extracellular matrix; phosphorylation; receptor serine/threonine kinase; signal transduction; SMAD; transcription; transforming growth factor-β; ubiquitylation 1.
    [Show full text]
  • Clinical Significance of Prognostic and Predictive Markers in Colorectal
    The Pharmacogenomics Journal (2002) 2, 209–216 2002 Nature Publishing Group All rights reserved 1470-269X/02 $25.00 www.nature.com/tpj CLINICAL IMPLICATION multiple genetic abnormalities are Clinical significance of prognostic accumulated over time during the pro- gression from adenoma to adenocarci- and predictive markers in colorectal noma (Figure 1).1 Mutations in genes such as the Kirsten-ras (K-ras), aden- cancer omatous polyposis coli (APC), deleted in colon cancer (DCC) and the p53 DB Longley, U McDermott and PG Johnston tumour suppressor gene are the most common genetic alterations found in Department of Oncology, Cancer Research Centre, Queen’s University Belfast, Belfast, sporadic CRC. Approximately 5% of Northern Ireland CRC is inherited and familial aden- omatous polyposis (FAP) and heredi- tary non-polyposis colon cancer The Pharmacogenomics Journal (2002) 2, fication and microsatellite instability (HNPCC) are the most well-charac- 209–216. doi:10.1038/sj.tpj.6500124 (MSI). In addition, the expression of terized syndromes.2 FAP is caused by individual genes can be assessed at the mutations in the APC gene, whereas INTRODUCTION levels of mRNA and protein using the 90% of HNPCC cases are caused by Colorectal cancer (CRC) is the second techniques of real-time reverse tran- mutations in genes involved in mis- most common cause of cancer death scription PCR and immunohistochem- match repair (MMR) leading to in the US. Approximately 130 000 new istry (IHC) respectively. The ultimate microsatellite instability (MSI). In cases of CRC are diagnosed in the US goal of this research is the tailoring of addition, 10–15% of sporadic cases of each year with an annual mortality of treatment to the molecular pheno- CRC have mutations in MMR genes.
    [Show full text]
  • IRF3 Prevents Colorectal Tumorigenesis Via Inhibiting the Nuclear Translocation of Β-Catenin
    ARTICLE https://doi.org/10.1038/s41467-020-19627-7 OPEN IRF3 prevents colorectal tumorigenesis via inhibiting the nuclear translocation of β-catenin Miao Tian1,7, Xiumei Wang1,7, Jihong Sun2,7, Wenlong Lin1, Lumin Chen2, Shengduo Liu3, Ximei Wu 4, ✉ ✉ Liyun Shi5, Pinglong Xu 3, Xiujun Cai 6 & Xiaojian Wang 1 Occurrence of Colorectal cancer (CRC) is relevant with gut microbiota. However, role of IRF3, a key signaling mediator in innate immune sensing, has been barely investigated in CRC. 1234567890():,; Here, we unexpectedly found that the IRF3 deficient mice are hyper-susceptible to the development of intestinal tumor in AOM/DSS and Apcmin/+ models. Genetic ablation of IRF3 profoundly promotes the proliferation of intestinal epithelial cells via aberrantly activating Wnt signaling. Mechanically, IRF3 in resting state robustly associates with the active β- catenin in the cytoplasm, thus preventing its nuclear translocation and cell proliferation, which can be relieved upon microbe-induced activation of IRF3. In accordance, the survival of CRC is clinically correlated with the expression level of IRF3. Therefore, our study identifies IRF3 as a negative regulator of the Wnt/β-catenin pathway and a potential prognosis marker for Wnt-related tumorigenesis, and describes an intriguing link between gut microbiota and CRC via the IRF3-β-catenin axis. 1 Institute of Immunology and Bone Marrow Transplantation Center, The First Affiliated Hospital, School of Medicine, Zhejiang University, 310003 Hangzhou, China. 2 Department of Radiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, 310016 Hangzhou, China. 3 The MOE Key Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, 310058 Hangzhou, China.
    [Show full text]
  • Nucleocytoplasmic Shuttling of Smad Proteins
    Cell Research (2009) 19:36-46. npg © 2009 IBCB, SIBS, CAS All rights reserved 1001-0602/09 $ 30.00 REVIEW www.nature.com/cr Nucleocytoplasmic shuttling of Smad proteins Caroline S Hill1 1Laboratory of Developmental Signalling, Cancer Research UK London Research Institute, 44 Lincoln’s Inn Fields, London WC2A 3PX, UK Nuclear accumulation of active Smad complexes is crucial for transduction of transforming growth factor β (TGF-β)- superfamily signals from transmembrane receptors into the nucleus. It is now clear that the nucleocytoplasmic distri- butions of Smads, in both the absence and the presence of a TGF-β-superfamily signal, are not static, but instead the Smads are continuously shuttling between the nucleus and the cytoplasm in both conditions. This article presents the evidence for continuous nucleocytoplasmic shuttling of Smads. It then reviews different mechanisms that have been proposed to mediate Smad nuclear import and export, and discusses how the Smad steady-state distributions in the absence and the presence of a TGF-β-superfamily signal are established. Finally, the biological relevance of continu- ous nucleocytoplasmic shuttling for signaling by TGF-β superfamily members is discussed. Keywords: Smad, nuclear import and export, TGF-β-superfamily signaling, karyopherin, nucleocytoplasmic shuttling Cell Research (2009) 19:36-46. doi: 10.1038/cr.2008.325; published online 30 December 2008 Introduction into three functional classes. The first class are the receptor-regulated Smads or R-Smads (Smad1, 2, 3, 5 The transforming growth factor b (TGF-b) superfam- and 8), which are phosphorylated by the type I receptor ily of ligands, which comprises TGF-bs, Activins, bone kinases on an SXS motif at their extreme C-termini.
    [Show full text]
  • Fos-Jun Interactions That Mediate Transcription Regulatory Speci®City
    Oncogene (2001) 20, 2438 ± 2452 ã 2001 Nature Publishing Group All rights reserved 0950 ± 9232/01 $15.00 www.nature.com/onc Close encounters of many kinds: Fos-Jun interactions that mediate transcription regulatory speci®city Yurii Chinenov1 and Tom K Kerppola*,1 1Howard Hughes Medical Institute, University of Michigan Medical School Ann Arbor, Michigan, MI 48109-0650, USA Fos and Jun family proteins regulate the expression of a Wang et al., 1992). However, only a few of the genes myriad of genes in a variety of tissues and cell types. that mediate the essential functions of speci®c Fos and This functional versatility emerges from their interac- Jun family members have been identi®ed (Bakin and tions with related bZIP proteins and with structurally Curran, 1999; Fu et al., 2000) unrelated transcription factors. These interactions at Fos and Jun family proteins function as dimeric composite regulatory elements produce nucleoprotein transcription factors that bind to AP-1 regulatory complexes with high sequence-speci®city and regulatory elements in the promoter and enhancer regions of selectivity. Several general principles including binding numerous mammalian genes (Curran and Franza, cooperativity and conformational adaptability have 1988). Jun proteins form both homodimers and emerged from studies of regulatory complexes containing heterodimers with Fos proteins, whereas Fos proteins Fos-Jun family proteins. The structural properties of do not form homodimers and require heterodimeriza- Fos-Jun family proteins including opposite orientations tion to bind DNA. The DNA-binding and dimerization of heterodimer binding and the ability to bend DNA can domains among dierent family members are highly contribute to the assembly and functions of such conserved and dierent members of the Fos and Jun complexes.
    [Show full text]
  • The Role of Smad Signaling in Hematopoiesis and Translational Hematology
    Leukemia (2011) 25, 1379–1388 & 2011 Macmillan Publishers Limited All rights reserved 0887-6924/11 www.nature.com/leu SPOTLIGHT REVIEW The role of Smad signaling in hematopoiesis and translational hematology U Blank and S Karlsson Division of Molecular Medicine and Gene Therapy, Laboratory Medicine, Lund Stem Cell Center, Lund University Hospital, Lund, Sweden Hematopoietic stem cells (HSCs) reside in the bone marrow ligands are reflected in vitro, often leading to opposing findings (BM) of adult individuals and function to produce and between in vitro and in vivo systems. regenerate the entire blood and immune system over the In this review, we will discuss the role of TGF-b and Smad course of an individual’s lifetime. Historically, HSCs are among the most thoroughly characterized tissue-specific stem cells. signaling in normal hematopoiesis, featuring aspects of transla- Despite this, the regulation of fate options, such as self-renewal tional hematology, particularly the role of Smad signaling in the and differentiation, has remained elusive, partly because of the development of hematologic malignancies and how the Smad expansive plethora of factors and signaling cues that govern circuitry may be exploited for the purpose of stem cell HSC behavior in vivo. In the BM, HSCs are housed in expansion. It should be emphasized that although some of the specialized niches that dovetail the behavior of HSCs with the findings discussed here come from studies of human and need of the organism. The Smad-signaling pathway, which operates downstream of the transforming growth factor-b patients’ cells, the majority of the data derive from studies in (TGF-b) superfamily of ligands, regulates a diverse set of bio- well-defined mouse models.
    [Show full text]
  • Specific Interactions Between Smad Proteins and AP-1
    Oncogene (2013) 32, 3606–3615 & 2013 Macmillan Publishers Limited All rights reserved 0950-9232/13 www.nature.com/onc ORIGINAL ARTICLE Specific interactions between Smad proteins and AP-1 components determine TGFb-induced breast cancer cell invasion A Sundqvist1, A Zieba2,5, E Vasilaki1,5, C Herrera Hidalgo1,OSo¨ derberg2, D Koinuma3, K Miyazono1,3, C-H Heldin1, U Landegren2, P ten Dijke1,4 and H van Dam1,4 Deregulation of the transforming growth factor b (TGFb) signal transduction cascade is functionally linked to cancer. In early phases, TGFb acts as a tumor suppressor by inhibiting tumor cell proliferation, whereas in late phases, it can act as a tumor promoter by stimulating tumor cell invasion and metastasis. Smad transcriptional effectors mediate TGFb responses, but relatively little is known about the Smad-containing complexes that are important for epithelial–mesenchymal transition and invasion. In this study, we have tested the hypothesis that specific members of the AP-1 transcription factor family determine TGFb signaling specificity in breast cancer cell invasion. Using a 3D model of collagen-embedded spheroids of MCF10A-MII premalignant human breast cancer cells, we identified the AP-1 transcription factor components c-Jun, JunB, c-Fos and Fra1 as essential factors for TGFb- induced invasion and found that various mesenchymal and invasion-associated TGFb-induced genes are co-regulated by these proteins. In situ proximity ligation assays showed that TGFb signaling not only induces complexes between Smad3 and Smad4 in the nucleus but also complexes between Smad2/3 and Fra1, whereas complexes between Smad3, c-Jun and JunB could already be detected before TGFb stimulation.
    [Show full text]
  • Coordinate Transcriptional and Translational Repression of P53 by TGF-B1 Impairs the Stress Response
    Molecular Cell Article Coordinate Transcriptional and Translational Repression of p53 by TGF-b1 Impairs the Stress Response Fernando J. Lo´ pez-Dı´az,1 Philippe Gascard,2 Sri Kripa Balakrishnan,1 Jianxin Zhao,2 Sonia V. del Rincon,3 Charles Spruck,3 Thea D. Tlsty,2 and Beverly M. Emerson1,* 1Regulatory Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA 2Department of Pathology, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA 3Sanford Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA *Correspondence: [email protected] http://dx.doi.org/10.1016/j.molcel.2013.04.029 SUMMARY been observed in human cancers (Saldan˜ a-Meyer and Recillas- Targa, 2011). Moreover, seminal studies have elegantly de- Cellular stress results in profound changes in RNA monstrated that de novo p53 translation mediated by the 60S and protein synthesis. How cells integrate this ribosomal protein RPL26 is required for efficient p53 accumula- intrinsic, p53-centered program with extracellular tion to direct specific cell-fate outcomes (Chen and Kastan, signals is largely unknown. We demonstrate that 2010; Schumacher et al., 2005; Takagi et al., 2005). b b TGF-b1 signaling interferes with the stress response Transforming growth factor (TGF- ) has a dual role in cancer through coordinate transcriptional and translational by acting as a tumor suppressor through cell-growth arrest and as a tumor facilitator at later stages (Massague´ , 2008). Central to repression of p53 levels, which reduces p53-acti- TGF-b1 signaling is phosphorylation of Smad 2/3 transcription vated transcription, and apoptosis in precancerous factors by the TGF-bRI/TGF-bRII receptor complex.
    [Show full text]