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Sumter TF, Xian L, Huso T, Koo M, Chang YT, Almasri TN, Chia L, Inglis C, Reid D, Resar LMS. The High Mobility Group A1 (HMGA1) Transcriptome in Cancer and Development. Curr Mol Med 2016; 16:353-93. [PMID: 26980699 DOI: 10.2174/1566524016666160316152147] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 02/15/2016] [Accepted: 03/10/2016] [Indexed: 01/19/2023]
Abstract
BACKGROUND & OBJECTIVES Chromatin structure is the single most important feature that distinguishes a cancer cell from a normal cell histologically. Chromatin remodeling proteins regulate chromatin structure and high mobility group A (HMGA1) proteins are among the most abundant, nonhistone chromatin remodeling proteins found in cancer cells. These proteins include HMGA1a/HMGA1b isoforms, which result from alternatively spliced mRNA. The HMGA1 gene is overexpressed in cancer and high levels portend a poor prognosis in diverse tumors. HMGA1 is also highly expressed during embryogenesis and postnatally in adult stem cells. Overexpression of HMGA1 drives neoplastic transformation in cultured cells, while inhibiting HMGA1 blocks oncogenic and cancer stem cell properties. Hmga1 transgenic mice succumb to aggressive tumors, demonstrating that dysregulated expression of HMGA1 causes cancer in vivo. HMGA1 is also required for reprogramming somatic cells into induced pluripotent stem cells. HMGA1 proteins function as ancillary transcription factors that bend chromatin and recruit other transcription factors to DNA. They induce oncogenic transformation by activating or repressing specific genes involved in this process and an HMGA1 "transcriptome" is emerging. Although prior studies reveal potent oncogenic properties of HMGA1, we are only beginning to understand the molecular mechanisms through which HMGA1 functions. In this review, we summarize the list of putative downstream transcriptional targets regulated by HMGA1. We also briefly discuss studies linking HMGA1 to Alzheimer's disease and type-2 diabetes. CONCLUSION Further elucidation of HMGA1 function should lead to novel therapeutic strategies for cancer and possibly for other diseases associated with aberrant HMGA1 expression.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - L M S Resar
- Department of Medicine, Faculty of the Johns Hopkins University School of Medicine, 720 Rutland Avenue, Ross Research Building, Room 1025, Baltimore, MD 21205-2109, USA.
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2
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Abstract
The high mobility group A (HMGA) non-histone chromatin proteins alter chromatin structure and thereby regulate the transcription of several genes by either enhancing or suppressing transcription factors. This protein family is implicated, through different mechanisms, in both benign and malignant neoplasias. Rearrangements of HMGA genes are a feature of most benign human mesenchymal tumours. Conversely, unrearranged HMGA overexpression is a feature of malignant tumours and is also causally related to neoplastic cell transformation. Here, we focus on the role of the HMGA proteins in human neoplastic diseases, the mechanisms by which they contribute to carcinogenesis, and therapeutic strategies based on targeting HMGA proteins.
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Affiliation(s)
- Alfredo Fusco
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Facoltà di Medicina e Chirurgia, Università degli Studi di Napoli "Federico II", via Pansini, 5, 80131, Naples, Italy.
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3
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Goenka S, Boothby M. Selective potentiation of Stat-dependent gene expression by collaborator of Stat6 (CoaSt6), a transcriptional cofactor. Proc Natl Acad Sci U S A 2006; 103:4210-5. [PMID: 16537510 PMCID: PMC1449672 DOI: 10.1073/pnas.0506981103] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The molecular mechanisms by which transcription is selectively activated and precisely controlled by signal transducer and activator of transcription (Stat) factors represent a central issue in cytokine-mediated cellular responses. Stat6 mediates responses to IL-4 and antagonizes Stat1 activated by IFN-gamma. We have discovered that Stat6 binds to collaborator of Stat6 (CoaSt6), a protein that lacks conventional coactivator motifs but contains three iterations of a domain found in the variant histone macroH2A. Although macroH2A participates in transcriptional silencing, the macro domains of CoaSt6 increased IL-4-induced gene expression. Moreover, CoaSt6 amplified Stat6-mediated but not IFN-gamma-induced gene expression, providing evidence of a selective coregulator of Stat-mediated gene transcription.
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Affiliation(s)
| | - Mark Boothby
- *Department of Microbiology and Immunology and
- Division of Rheumatology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232-2363
- To whom correspondence should be addressed. E-mail:
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4
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Lin SC. Identification of an NF-Y/HMG-I(Y)-binding site in the human IL-10 promoter. Mol Immunol 2005; 43:1325-31. [PMID: 16256199 DOI: 10.1016/j.molimm.2005.09.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2005] [Accepted: 09/24/2005] [Indexed: 11/29/2022]
Abstract
The cis-acting elements and transcriptional factors that control interleukin 10 (IL-10) promoter activity remain to be clarified. In this report, by performing electrophoresis mobility shift assay (EMSA) with nuclear extracts from the Raji B cell line, the nuclear factor Y (NF-Y) was found to be capable of binding to a CCAAT box-containing region between the -215 and -192bps (the -215/-192 region), relative to the transcription initiation site, in the human IL-10 promoter. The binding of NF-Y to the promoter appears to be enhanced by the presence of HMG-I(Y), since anti-HMG-I(Y) antibody diminished the NF-Y-binding activity in EMSA. Two T nucleotides at -192 and -193bps were found to be critical for the binding of NF-Y and HMG-I(Y) to the -215/-192 promoter region, suggesting the possibility that HMG-I(Y) binds to the AT-rich promoter region downstream of the CCAAT box at the -210/-199 region. These findings suggest that NF-Y and HMG-I(Y) may play an important role in regulating the IL-10 promoter activity in B cells.
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Affiliation(s)
- Shih-Chang Lin
- Division of Allergy and Immunology, Department of Internal Medicine, Cathay General Hospital, Taipei, Taiwan.
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5
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Sandberg AA. Updates on the cytogenetics and molecular genetics of bone and soft tissue tumors: leiomyoma. ACTA ACUST UNITED AC 2005; 158:1-26. [PMID: 15771900 DOI: 10.1016/j.cancergencyto.2004.08.025] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Revised: 08/11/2004] [Accepted: 08/11/2004] [Indexed: 12/22/2022]
Affiliation(s)
- Avery A Sandberg
- Department of DNA Diagnostics, St. Joseph's Hospital and Medical Center, 350 West Thomas Road, Phoenix, AZ 85013, USA.
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6
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Kelly-Welch AE, Wang HY, Wang LM, Pierce JH, Jay G, Finkelman F, Keegan AD. Transgenic Expression of Insulin Receptor Substrate 2 in Murine B Cells Alters the Cell Density-Dependence of IgE Production In Vitro and Enhances IgE Production In Vivo. THE JOURNAL OF IMMUNOLOGY 2004; 172:2803-10. [PMID: 14978080 DOI: 10.4049/jimmunol.172.5.2803] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Previous studies have shown that insulin receptor substrate (IRS)1 and IRS2 mediate proliferative and antiapoptotic signaling through the IL-4R in 32D cells; however their role in regulating normal B cell responses is not clear. To investigate the role of IRS2 in normal B cell function, we developed IRS2 transgenic (Tg) mice on the C57BL/6 background. Western blot analysis revealed a 2-fold elevation in IRS2 protein levels in Tg(+) mice compared with littermate controls and a 3-fold increase in basal tyrosine phosphorylated IRS2 in the absence of IL-4 stimulation. IL-4-induced tyrosine phosphorylation of IRS2 was elevated in Tg(+) B cells, whereas IL-4-induced phosphorylation of STAT6 was similar between Tg(+) and Tg(-) B cells. Tg expression of IRS2 had little effect on IL-4-mediated proliferation and no effect on protection from apoptosis. However, production of IgE and IgG1 by Tg(+) B cells using standard in vitro conditions was diminished 50-60%. Because Ig production in vitro is known to be highly cell concentration-dependent, we performed experiments at different cell concentrations. Interestingly, at very low B cell concentrations (1000-5000 B cells/well), IgE and IgG1 production by Tg(+) B cells was greater than that of controls, whereas at higher cell concentrations (10,000-20,000 cells/well) Ig production by Tg(+) B cells was less than controls. Furthermore, in vivo immunization with OVA-alum or goat anti-IgD resulted in elevated serum IgE levels in the Tg(+) mice. These results indicate that overexpression of IRS2 alters the B cell intrinsic density-dependence of IgE and IgG1 production in vitro and enhances IgE responses in vivo.
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Affiliation(s)
- Ann E Kelly-Welch
- Department of Immunology, Jerome Holland Laboratories, American Red Cross, Rockville, MD 20855, USA
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7
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Affiliation(s)
- Jay L Hess
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, 413b Stellar-Chance Laboratories, 422 Curie Boulevard, Philadelphia, PA 19104-6100, USA.
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8
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Abstract
The HMG-I/Y gene encodes the HMG-I and -Y architectural, chromatin binding proteins originally identified based on their association with chromosomal DNA. HMG-I/Y proteins bind to AT-rich regions in chromosomal DNA and alter gene expression. Increased HMG-I/Y protein expression also correlates with neoplastic transformation. Previous work from our laboratory has shown that HMG-I/Y is a direct c-Myc target gene involved in neoplastic transformation in Burkitt's lymphoma. We also observed that HMG-I/Y proteins have several oncogenic properties. In this report, we show that HMG-I/Y proteins are increased in several human breast cancer cell lines compared to a human breast cell line derived from normal breast cells. Decreasing HMG-I/Y proteins using an antisense ribozyme approach inhibits transformation in human breast cancer cells, suggesting that HMG-I/Y is important for the transformed phenotype observed in these cells. In addition, increased expression of the HMG-I isoform in normal human breast cells leads to transformation. These results suggest that HMG-I/Y is an oncogene important in the pathogenesis of human breast cancer. Although additional studies with animal models are needed, the antisense experiments, which result in blocking transformation suggest that this approach may have therapeutic potential in patients with breast cancer characterized by increased HMG-I/Y expression.
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Affiliation(s)
- Christine E Dolde
- Department of Pediatrics, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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9
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Liu F, Chau KY, Arlotta P, Ono SJ. The HMG I proteins: dynamic roles in gene activation, development, and tumorigenesis. Immunol Res 2002; 24:13-29. [PMID: 11485207 DOI: 10.1385/ir:24:1:13] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The high mobility group I, Y, and I-C proteins are low-molecular-weight, nonhistone chromosomal proteins that play a general role modulating gene expression during development and the immune response. Consistent with their role in early development, all three proteins are expressed at high levels during embryogenesis, and their expression is markedly diminished in differentiated cells. Exceptions to the general repression of these genes in adult tissues involve (1) A burst of synthesis of the HMG I protein during the immune response (during lymphocyte activation and preceding cytokine/adhesion molecule gene expression), (2) A constitutive expression of the HMG I and Y proteins in photoreceptor cells, and (3) Derepression of HMG I, Y, and often I-C expression in neoplastic cells. Work from several laboratories has now uncovered how these proteins participate in gene activation: (1) By altering the chromatin structure around an inducible gene-and thus influencing accessibility of the locus to regulatory proteins-(2) By facilitating the loading of transcription factors onto the promoters, and (3) By bridging adjacent transcription factors on a promoter via protein/protein interactions. Despite the similar structures and biochemical properties of the three proteins, the work has also provided clues to a division of labor between these proteins. HMG I and Y have demonstrable roles in enhanceosome formation, whereas HMG I-C has a specific role in adipogenesis. C-terminal truncations of HMG I-C and wild-type HMG Y appear to function in a manner analogous to oncogenes, as assessed by cellular transforation assays and transgenic mice. Future work should clearly define the similarities and differences in the biological roles of the three proteins, and should evolve to include attempts at pharmaceutical intervention in disease, based upon structural information concerning HMG I interactions with DNA and with regulatory proteins.
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Affiliation(s)
- F Liu
- University College London, Institute of Ophthalmology, UK
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10
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Boothby M, Mora AL, Aronica MA, Youn J, Sheller JR, Goenka S, Stephenson L. IL-4 signaling, gene transcription regulation, and the control of effector T cells. Immunol Res 2002; 23:179-91. [PMID: 11444383 DOI: 10.1385/ir:23:2-3:179] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The central goal of our laboratory is to understand the regulation of lymphoid cells through molecular mechanisms of signal transduction and transcriptional control. A long-standing focus has been on changes that influence the effector function of mature lymphocytes. Work in the laboratory is oriented toward the identification of new regulatory mechanisms using cell lines and primary cells, and the validation of these in vitro findings in mouse models of immune responses and diseases. In this review, we summarize key insights into the regulation of T helper cell function during the phase of immunity where effector responses arise de novo. Particular interest has been centered on cytokine gene regulation as part of T cell differentiation into the Th1 and Th2 subsets. Information on IL-4 receptor signaling and the role of NF-kappaB transcription factors is reviewed. Our more recent work is designed to understand how regulation at the Th1/2 effector stages is related to the control of memory T cell survival, immune recall responses, and the role of these responses in immune-mediated disease.
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Affiliation(s)
- M Boothby
- Department of Microbiology and Immunology, Vanderbilt University Medical School, Nashville, TN 37232-2363, USA.
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12
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Rabah D, Grant S, Ma C, Conrad DH. Bryostatin-1 specifically inhibits in vitro IgE synthesis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 167:4910-8. [PMID: 11673496 DOI: 10.4049/jimmunol.167.9.4910] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Bryostatin-1, a macrocyclic lactone, is an antineoplastic agent that potently activates protein kinase C. Bryostatin-1 (Bryo) had an immunomodulatory effect on murine B cells in that it specifically inhibited IgE production. IgE levels were inhibited in a B cell dose-response curve, whereas IgM and IgG1 were induced by Bryo treatment. Taken together, ELISPOT and surface Ig staining data suggested that Bryo inhibition occurred at the level of class switching. RT-PCR and real time PCR data showed that this inhibition was achieved at an early step in switch recombination, namely, the appearance of Iepsilon germline transcripts. Although Bryo caused a delay in the proliferative response of IL-4/CD40 ligand trimer-stimulated B cells, CFSE studies revealed that the Bryo-mediated inhibition of class switching to IgE occurred independently of the number of division cycles. Notably, Bryo showed the same specific IgE inhibition in human B cells. This study provides evidence for a unique mechanism regulating IgE production possibly downstream of PKC by specifically modulating Iepsilon germline transcription.
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Affiliation(s)
- D Rabah
- Department of Microbiology, Virginia Commonwealth University, Richmond, VA 23298, USA
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13
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Shannon MF, Coles LS, Attema J, Diamond P. The role of architectural transcription factors in cytokine gene transcription. J Leukoc Biol 2001. [DOI: 10.1189/jlb.69.1.21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- M. F. Shannon
- Division of Biochemistry and Molecular Biology, John Curtin School of Medical Research, Australian National University, Canberra
| | - L. S. Coles
- Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science, Adelaide, South Australia
| | - J. Attema
- Division of Biochemistry and Molecular Biology, John Curtin School of Medical Research, Australian National University, Canberra
| | - P. Diamond
- Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science, Adelaide, South Australia
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14
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Beaujean N, Bouniol-Baly C, Monod C, Kissa K, Jullien D, Aulner N, Amirand C, Debey P, Käs E. Induction of early transcription in one-cell mouse embryos by microinjection of the nonhistone chromosomal protein HMG-I. Dev Biol 2000; 221:337-54. [PMID: 10790330 DOI: 10.1006/dbio.2000.9668] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the mouse embryo, the onset of zygotic transcription occurs at the end of the first cell cycle, upon completion of DNA replication. We show that the nonhistone chromosomal protein HMG-I, whose translocation into the pronuclei of one-cell embryos is linked to this first round of DNA synthesis, plays a critical role in the activation of zygotic transcription. Indeed, microinjection of purified HMG-I results in a higher nuclear accumulation of the protein and triggers an earlier activation of zygotic transcription, an effect which is abolished by the preincubation of the protein with a specific antibody directed against its AT-hook DNA-binding motifs. Significantly, microinjection of this antibody also prevents the normal onset of transcription in the embryo, suggesting that endogenous HMG-I is similarly involved in this process. Finally, microinjection of the exogenous protein modifies chromatin structure as measured by in situ accessibility to DNase I. We propose that general chromosomal architectural factors such as HMG-I can modulate the accessibility of chromatin to specialized regulatory factors, thereby promoting a transcriptionally competent state.
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Affiliation(s)
- N Beaujean
- Institut de Biologie Physico-Chimique, INRA 806/EA 2703, IFR 63, Muséum National d'Histoire Naturelle, 13 Rue Pierre et Marie Curie, Paris, 75005, France
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15
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Klotzbücher M, Wasserfall A, Fuhrmann U. Misexpression of wild-type and truncated isoforms of the high-mobility group I proteins HMGI-C and HMGI(Y) in uterine leiomyomas. THE AMERICAN JOURNAL OF PATHOLOGY 1999; 155:1535-42. [PMID: 10550310 PMCID: PMC1866973 DOI: 10.1016/s0002-9440(10)65469-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/21/1999] [Indexed: 10/18/2022]
Abstract
High-mobility group I (HMGI) proteins are architectural transcription factors expressed predominantly during embryonic development. Their genetic loci are the most frequent targets of chromosomal rearrangements in uterine leiomyomas and other benign tumors. It was therefore suggested that both HMGI genes are involved in the neoplastic transformation of benign tumors. By Western analysis we found that 16 of 33 uterine leiomyomas expressed high levels of HMGI-C or HMGI(Y) proteins, whereas they were not detected in the corresponding myometrium. Immunohistochemistry demonstrated that the expression of HMGI-C is restricted to leiomyoma smooth muscle cells but is not expressed in vascular smooth muscle cells or the connective tissue of the tumor. Northern blotting confirmed the protein expression data for HMGI-C, whereas HMGI(Y) mRNA and protein levels did not correlate, suggesting that posttranscriptional mechanisms are involved in the regulation of HMGI(Y) expression. Three of the uterine leiomyomas analyzed expressed HMGI-C gene products with altered molecular weight. Two of them were proved to consist of the entire DNA-binding domain but lacked sequences of the C-terminal acidic tail. Conversely, other tumors expressed HMGI-C or HMGI(Y) genes that were not affected by mutations of the coding region. Thus we identified uterine leiomyomas that expressed mutated HMGI-C, whereas other uterine leiomyomas expressed wild-type HMGI-C or HMGI(Y). On the basis of our data we assume that the enhanced expression of functionally active HMGI proteins, whether they are wild-type or not, is important for the pathogenesis of uterine leiomyomas.
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Affiliation(s)
- M Klotzbücher
- Research Laboratories of Schering AG, Berlin, Germany
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16
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Reeves R, Nissen MS. Purification and assays for high mobility group HMG-I(Y) protein function. Methods Enzymol 1999; 304:155-88. [PMID: 10372360 DOI: 10.1016/s0076-6879(99)04011-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
MESH Headings
- Animals
- Base Sequence
- Cell Fractionation/methods
- Cell Nucleus/chemistry
- Cell Nucleus/ultrastructure
- Centrifugation/methods
- Chromatin/chemistry
- Chromatin/ultrastructure
- Chromatography, High Pressure Liquid/methods
- Chromatography, Ion Exchange/methods
- DNA Footprinting/methods
- DNA, Superhelical/chemistry
- DNA, Superhelical/isolation & purification
- DNA, Superhelical/metabolism
- Deoxyribonuclease I
- HMGA1a Protein
- HeLa Cells
- High Mobility Group Proteins/analysis
- High Mobility Group Proteins/isolation & purification
- High Mobility Group Proteins/metabolism
- Humans
- Indicators and Reagents
- Interleukin-4/genetics
- Leukemia, Erythroblastic, Acute/metabolism
- Leukemia, Erythroblastic, Acute/pathology
- Mice
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Neoplasm Proteins/isolation & purification
- Plasmids
- Receptors, Interleukin-2/genetics
- Recombinant Proteins/analysis
- Recombinant Proteins/isolation & purification
- Recombinant Proteins/metabolism
- Transcription Factors/analysis
- Transcription Factors/isolation & purification
- Transcription Factors/metabolism
- Transfection
- Tumor Cells, Cultured
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Affiliation(s)
- R Reeves
- Department of Biochemistry/Biophysics, Washington State University, Pullman 99164-4660, USA
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17
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Nelms K, Keegan AD, Zamorano J, Ryan JJ, Paul WE. The IL-4 receptor: signaling mechanisms and biologic functions. Annu Rev Immunol 1999; 17:701-38. [PMID: 10358772 DOI: 10.1146/annurev.immunol.17.1.701] [Citation(s) in RCA: 1193] [Impact Index Per Article: 47.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Interleukin-4 is a multifunctional cytokine that plays a critical role in the regulation of immune responses. Its effects depend upon binding to and signaling through a receptor complex consisting of the IL-4R alpha chain and the common gamma chain (gamma c), resulting in a series of phosphorylation events mediated by receptor-associated kinases. In turn, these cause the recruitment of mediators of cell growth, of resistance to apoptosis, and of gene activation and differentiation. Here we describe our current understanding of the organization of the IL-4 receptor, of the signaling pathways that are induced as a result of receptor occupancy, and of the various mechanisms through which receptor function is modulated. We particularly emphasize the modular nature of the receptor and the specialization of different receptor regions for distinct functions, most notably the independent regulation of cell growth and gene activation.
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Affiliation(s)
- K Nelms
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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18
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Chase MB, Haga SB, Hankins WD, Williams DM, Bi Z, Strovel JW, Obriecht C, Berg PE. Binding of HMG-I(Y) elicits structural changes in a silencer of the human beta-globin gene. Am J Hematol 1999; 60:27-35. [PMID: 9883803 DOI: 10.1002/(sici)1096-8652(199901)60:1<27::aid-ajh6>3.0.co;2-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Proteins involved in repression of the human beta-globin gene may be useful in the treatment of sickle cell anemia, in conjunction with therapy to reactivate fetal globin genes. If there is a reciprocal elevation of gamma-globin expression upon repression, this approach could be useful in additional hemoglobinopathies. We previously showed that repression of the beta-globin gene appears to be mediated through two DNA sequences, silencers I and II, and identified a protein termed BP1 which binds to both silencer sequences. In this study, we cloned two cDNAs encoding proteins which bind to an oligonucleotide in silencer I containing a BP1 binding site. These cDNAs correspond to HMG-I and HMG-Y, isoforms regarded as architectural proteins. We demonstrate that binding of HMG-I(Y) to this oligonucleotide causes bending/flexure of the DNA. HMG-I(Y) also binds to a second oligonucleotide containing a BP1 binding site located in a negative control region upstream of the delta-globin gene, suggesting a role for HMG-I(Y) in repression of adult globin genes. Expression studies revealed that HMG-I(Y) is ubiquitously expressed in human tissues that do not express beta-globin, being present in 48 of 50 tissues and six hematopoietic cell lines examined. Furthermore, HMG-I(Y) expression is down-regulated during differentiation of primary erythroid cells. We present a model in which HMG-I(Y) alters DNA conformation to allow binding of repressor proteins, and in which the relative amount of HMG-I(Y) helps to determine the repressive state of the beta-globin gene.
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Affiliation(s)
- M B Chase
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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19
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Morton CC. Warner-Lambert/Parke-Davis Award lecture. Many tumors and many genes: genetics of uterine leiomyomata. THE AMERICAN JOURNAL OF PATHOLOGY 1998; 153:1015-20. [PMID: 9777932 PMCID: PMC1853042 DOI: 10.1016/s0002-9440(10)65645-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- C C Morton
- Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
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20
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Reeves R, Nissen MS. Cell cycle regulation and functions of HMG-I(Y). PROGRESS IN CELL CYCLE RESEARCH 1998; 1:339-49. [PMID: 9552376 DOI: 10.1007/978-1-4615-1809-9_28] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Members of the HMG-I(Y) family of "high mobility group" (HMG) proteins are distinguished from other nonhistone chromatin proteins by their ability to preferentially recognize the structure of the narrow minor groove of A.T-sequences of B-form DNA. In vivo the HMG-I(Y) proteins are localized in the A.T-rich G/Q bands and in the "scaffold-associated regions" (SARs) of metaphase chromosomes. These proteins also share with some of the other "HMG box" proteins the ability to recognize non-B-form structures, such as cruciforms (four-way junctions), as well as the possessing the capacity to introduce both bends and supercoils in substrate DNAs. These characteristics, along with their ability to specifically interact with a number of known transcription factors, enable the HMG-I(Y) proteins to function in vivo as structural transcription factors for a number mammalian genes. The HMG-I(Y) proteins are also in vivo substrates for the cell cycle regulated Cdc2 kinase which phosphorylates the DNA-binding domain(s) of the protein and, as a result, decreases their substrate binding affinity. This reversible in vivo pattern of Cdc2 kinase phosphorylations during the cell cycle is likely to play a major role in mediating the biological function(s) of the HMG-I(Y) proteins.
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Affiliation(s)
- R Reeves
- Department of Biochemistry/Biophysics, Washington State University, Pullman 99164-4660, USA
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21
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Keegan AD, Zamorano J. Regulation of gene expression, growth, and cell survival by IL-4: contribution of multiple signaling pathways. Cell Res 1998; 8:1-13. [PMID: 9570012 DOI: 10.1038/cr.1998.1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Interleukin-4 is a cytokine produced by activated T cells, mast cells, and basophils that elicits many important biological responses[1] (see Tab 1). These responses range from the regulation of helper T cell differentiation[2] and the production of IgE[3] to the regulation of the adhesive properties of endothelial cells via VCAM-1[4]. In keeping with these diverse biological effects, high-affinity binding sites for IL-4 (Kd 20 to 300 pM) have been detected on many hematopoietic and non-hematopoietic cell types at levels ranging from 50 to 5000 sites per cell[5]. This review will focus on the discrete signal transduction pathways activated by the IL-4 receptor and the coordination of these individual pathways in the regulation of a final biological outcome.
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Affiliation(s)
- A D Keegan
- Department of Immunology, Jerome H. Holland Laboratory, American Red Cross, Rockville, MD, USA
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22
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Arlotta P, Rustighi A, Mantovani F, Manfioletti G, Giancotti V, Tell G, Damante G. High mobility group I proteins interfere with the homeodomains binding to DNA. J Biol Chem 1997; 272:29904-10. [PMID: 9368066 DOI: 10.1074/jbc.272.47.29904] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Homeodomains (HDs) constitute the DNA binding domain of several transcription factors that control cell differentiation and development in a wide variety of organisms. Most HDs recognize sequences that contain a 5'-TAAT-3' core motif. However, the DNA binding specificity of HD-containing proteins does not solely determine their biological effects, and other molecular mechanisms should be responsible for their ultimate functional activity. Interference by other factors in the HD/DNA interaction could be one of the processes by which HD-containing proteins achieve the functional complexity required for their effects on the expression of target genes. Using gel-retardation assay, we demonstrate that two members of the high mobility group I (HMGI) family of nuclear proteins (HMGI-C and HMGY) can bind to a subset of HD target sequences and inhibit HDs from binding to the same sequences. The inhibition of the HD/DNA interaction occurs while incubating HMGI-C with DNA either before or after the addition of the HD. The reduced half-life of the HD.DNA complex in the presence of HMGI-C, and the shift observed in the CD spectra recorded upon HMGI-C binding to DNA, strongly suggest that structural modifications of the DNA are responsible for the inhibition of the HD.DNA complex formation. Moreover, by co-transfection experiments we provide evidence that this inhibition can occur also in vivo. The data reported here would suggest that HMGI proteins may be potential regulators of the function of HD-containing proteins and that they are able to interfere with the access of the HD to their target genes.
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Affiliation(s)
- P Arlotta
- Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, Università di Trieste, 34100 Trieste, Italy
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23
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Wang D, Zamorano J, Keegan AD, Boothby M. HMG-I(Y) phosphorylation status as a nuclear target regulated through insulin receptor substrate-1 and the I4R motif of the interleukin-4 receptor. J Biol Chem 1997; 272:25083-90. [PMID: 9312117 DOI: 10.1074/jbc.272.40.25083] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Interleukin (IL)-4 is a cytokine that regulates both the growth and differentiation of hematopoietic cells. Its ligand binding specificity and important signal transduction mechanisms are conferred by the IL-4 receptor alpha chain (IL-4Ralpha). The I4R is a tyrosine-containing motif within IL-4Ralpha that is critical for proliferative responses to IL-4. Although the I4R also contributes to gene regulation, nuclear targets directly regulated by this motif have not been described. It is shown here that the tyrosine at position 497 in the I4R is critical for regulation of the phosphorylation status of a set of nuclear proteins that includes HMG-I(Y), small non-histone chromosomal proteins involved in the control of gene expression in hematopoietic cell lines. Moreover, IL-4 is unable to induce HMG-I(Y) phosphorylation in insulin receptor substrate-1-deficient cells, and the inhibitor wortmannin completely blocks IL-4 regulation of HMG-I(Y) phosphorylation status but not activation of an IL-4 Stat protein. Taken together, these data indicate that HMG-I(Y) is a nuclear target whose phosphorylation status is regulated through the I4R motif via insulin receptor substrate proteins, independent of activation of the Stat pathway.
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Affiliation(s)
- D Wang
- Department of Microbiology & Immunology, Vanderbilt University Medical School, Nashville, Tennessee 37232-2363, USA
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24
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Klein-Hessling S, Schneider G, Heinfling A, Chuvpilo S, Serfling E. HMG I(Y) interferes with the DNA binding of NF-AT factors and the induction of the interleukin 4 promoter in T cells. Proc Natl Acad Sci U S A 1996; 93:15311-6. [PMID: 8986808 PMCID: PMC26401 DOI: 10.1073/pnas.93.26.15311] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
HMG I(Y) proteins bind to double-stranded A + T oligonucleotides longer than three base pairs. Such motifs form part of numerous NF-AT-binding sites of lymphokine promoters, including the interleukin 4 (IL-4) promoter. NF-AT factors share short homologous peptide sequences in their DNA-binding domain with NF-kappa B factors and bind to certain NF-kappa B sites. It has been shown that HMG I(Y) proteins enhance NF-kappa B binding to the interferon beta promoter and virus-mediated interferon beta promoter induction. We show that HMG I(Y) proteins exert an opposite effect on the DNA binding of NF-AT factors and the induction of the IL-4 promoter in T lymphocytes. Introduction of mutations into a high-affinity HMG I(Y)-binding site of the IL-4 promoter, which decreased HMG I(Y)-binding to a NF-AT-binding sequence, the Pu-bB (or P) site, distinctly increased the induction of the IL-4 promoter in Jurkat T leukemia cells. High concentrations of HMG I(Y) proteins are able to displace NF-ATp from its binding to the Pu-bB site. High HMG I(Y) concentrations are typical for Jurkat cells and peripheral blood T lymphocytes, whereas E14 T lymphoma cells and certain T helper type 2 cell clones contain relatively low HMG I(Y) concentrations. Our results indicate that HMG I(Y) proteins do not cooperate, but instead compete with NF-AT factors for the binding to DNA even though NF-AT factors share some DNA-binding to DNA even though NF-AT factors share some DNA-binding properties with NF-kB factors. This competition between HMG I(Y) and NF-AT proteins for DNA binding might be due to common contacts with minor groove nucleotides of DNA and may be one mechanism contributing to the selective IL-4 expression in certain T lymphocyte populations, such as T helper type 2 cells.
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Affiliation(s)
- S Klein-Hessling
- Department of Molecular Pathology, University of Würzburg, Germany
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25
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Lin SC, Stavnezer J. Activation of NF-kappaB/Rel by CD40 engagement induces the mouse germ line immunoglobulin Cgamma1 promoter. Mol Cell Biol 1996; 16:4591-603. [PMID: 8756615 PMCID: PMC231458 DOI: 10.1128/mcb.16.9.4591] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Interaction between CD40 on B cells and CD40 ligand (CD40L) on T cells has been shown to mediate T-cell contact help for B-cell proliferation, differentiation, and immunoglobulin isotype switching. It has recently been shown that cross-linking CD40 on mouse B cells induces germ line gamma1 and epsilon transcripts and that interleukin-4 synergizes with CD40 signaling to further induce these germ line transcripts. Germ line transcripts have been shown to be required for class switch recombination. Here we show that signaling via CD40 increases expression of a transiently transfected luciferase reporter plasmid driven by the germ line Cgamma1 promoter in M12.4.1 B-lymphoma cells. By linker-scanning mutation analysis of the promoter, we have identified a CD40-responsive region (CD40RR) which is able to confer inducibility by CD40L to a minimal c-fos promoter. The CD40RR contains three binding sites for NF-kappaB/Rel proteins which are each required for maximal induction of CD40RR activity by CD40L. Binding of the NF-kappaB/Rel proteins p50, p65, c-Rel, and RelB to the CD40RR is induced by CD40 signaling in M12.4.1 cells and in splenic B cells. Cotransfection of expression plasmids for p50 and p65 or p50 and RelB, but not c-Rel, into M12.4.1 cells transactivates the CD40RR and the germ line gamma1 promoter. These data demonstrate that NF-kappaB Rel proteins activated by CD40 ligation play an important role in induction of the germ line Cgamma1 promoter.
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Affiliation(s)
- S C Lin
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worecester 01655-0122, USA
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26
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Bustin M, Reeves R. High-mobility-group chromosomal proteins: architectural components that facilitate chromatin function. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1996; 54:35-100. [PMID: 8768072 DOI: 10.1016/s0079-6603(08)60360-8] [Citation(s) in RCA: 568] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- M Bustin
- Laboratory of Molecular Carcinogenesis, National Cancer Institute, National Institute of Health, Bethesda, Maryland 20892, USA
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27
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Abstract
Rapamycin has potent immunosuppressive properties reflecting its ability to disrupt cytokine signaling that promotes lymphocyte growth and differentiation. In IL-2-stimulated T cells, rapamycin impedes progression through the G1/S transition of the proliferation cycle, resulting in a mid-to-late G1 arrest. Two major biochemical alterations underlie this mode of action. The first one affects the phosphorylation/activation of the p70 S6 kinase (p70s6k), an early event of cytokine-induced mitogenic response. By inhibiting this enzyme, whose major substrate is the 40S ribosomal subunit S6 protein, rapamycin reduces the translation of certain mRNA encoding for ribosomal proteins and elongation factors, thereby decreasing protein synthesis. A second, later effect of rapamycin in IL-2-stimulated T cells is an inhibition of the enzymatic activity of the cyclin-dependent kinase cdk2-cyclin E complex, which functions as a crucial regulator of G1/S transition. This inhibition results from a prevention of the decline of the p27 cdk inhibitor, that normally follows IL-2 stimulation. To mediate these biochemical alterations, rapamycin needs to bind to intracellular proteins, termed FKBP, thereby forming a unique effector molecular complex. However, neither(p70s6k) inhibition, nor p27-induced cdk2-cyclin E inhibition are directly caused by the FKBP-rapamycin complex. Instead, this complex physically interacts with a novel protein, designated "mammalian target of rapamycin" (mTOR), which has sequence homology with the catalytic domain of phosphatidylinositol kinases and may therefore be itself a kinase. mTOR may act upstream of (p70s6K) and cdk2-cyclin E in a linear or bifurcated pathway of growth regulation. Molecular dissection of this pathway should further unravel cytokine-mediated signaling processes and help devise new immunosuppressants.
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Affiliation(s)
- F J Dumont
- Department of Immunology, Merck Research Laboratories, Rahway, NJ 07065, USA
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28
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Wang DZ, Ray P, Boothby M. Interleukin 4-inducible phosphorylation of HMG-I(Y) is inhibited by rapamycin. J Biol Chem 1995; 270:22924-32. [PMID: 7559428 DOI: 10.1074/jbc.270.39.22924] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The non-histone chromosomal protein HMG-I(Y) participates in repression of transcription directed by a promoter which confers interleukin 4 (IL-4)-inducible activation in transfected B cell lines. Metabolic labeling, phosphoamino acid analyses, and in vitro phosphorylation studies demonstrate that IL-4 induces serine phosphorylation of HMG-I(Y) in B lymphocytes. Phosphopeptide mapping shows that the predominant site of phosphorylation contains a casein kinase II consensus motif. The immunosuppressive agent rapamycin has been shown preferentially to inhibit IgE production by IL-4-treated human B cells. It is shown here that rapamycin inhibits both activation of the human germ line epsilon promoter by IL-4 and IL-4-inducible phosphorylation of HMG-I(Y). These findings demonstrate a rapamycin-sensitive pathway that transduces signals from the IL-4 receptor to nuclear factors that regulate inducible transcription. The affinity of normal nuclear HMG-I(Y) for DNA is increased by dephosphorylation in vitro, whereas in vitro kinase reactions using casein kinase II decrease recombinant HMG-I(Y) binding to DNA. These data further suggest a novel mechanism in which phosphorylation triggered by IL-4 or other cytokines could regulate the effects of HMG-I(Y) on gene transcription.
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Affiliation(s)
- D Z Wang
- Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2363, USA
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