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1.
J Allergy Clin Immunol ; 133(5): 1400-9, 1409.e1-5, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24589341

RESUMO

BACKGROUND: Identifying genetic syndromes that lead to significant atopic disease can open new pathways for investigation and intervention in allergy. OBJECTIVE: We sought to define a genetic syndrome of severe atopy, increased serum IgE levels, immune deficiency, autoimmunity, and motor and neurocognitive impairment. METHODS: Eight patients from 2 families with similar syndromic features were studied. Thorough clinical evaluations, including brain magnetic resonance imaging and sensory evoked potentials, were performed. Peripheral lymphocyte flow cytometry, antibody responses, and T-cell cytokine production were measured. Whole-exome sequencing was performed to identify disease-causing mutations. Immunoblotting, quantitative RT-PCR, enzymatic assays, nucleotide sugar, and sugar phosphate analyses, along with matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry of glycans, were used to determine the molecular consequences of the mutations. RESULTS: Marked atopy and autoimmunity were associated with increased T(H)2 and T(H)17 cytokine production by CD4(+) T cells. Bacterial and viral infection susceptibility were noted along with T-cell lymphopenia, particularly of CD8(+) T cells, and reduced memory B-cell numbers. Apparent brain hypomyelination resulted in markedly delayed evoked potentials and likely contributed to neurologic abnormalities. Disease segregated with novel autosomal recessive mutations in a single gene, phosphoglucomutase 3 (PGM3). Although PGM3 protein expression was variably diminished, impaired function was demonstrated by decreased enzyme activity and reduced uridine diphosphate-N-acetyl-D-glucosamine, along with decreased O- and N-linked protein glycosylation in patients' cells. These results define a new congenital disorder of glycosylation. CONCLUSIONS: Autosomal recessive hypomorphic PGM3 mutations underlie a disorder of severe atopy, immune deficiency, autoimmunity, intellectual disability, and hypomyelination.


Assuntos
Doenças Autoimunes/genética , Transtornos Cognitivos/genética , Imunodeficiência de Variável Comum/genética , Doenças Genéticas Inatas/genética , Hipersensibilidade/genética , Mutação , Fosfoglucomutase/genética , Doenças Autoimunes/enzimologia , Doenças Autoimunes/imunologia , Doenças Autoimunes/patologia , Linfócitos B/enzimologia , Linfócitos B/imunologia , Linfócitos B/patologia , Linfócitos T CD8-Positivos/enzimologia , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/patologia , Criança , Pré-Escolar , Transtornos Cognitivos/enzimologia , Transtornos Cognitivos/imunologia , Transtornos Cognitivos/patologia , Imunodeficiência de Variável Comum/enzimologia , Imunodeficiência de Variável Comum/imunologia , Imunodeficiência de Variável Comum/patologia , Família , Feminino , Doenças Genéticas Inatas/enzimologia , Doenças Genéticas Inatas/imunologia , Doenças Genéticas Inatas/patologia , Humanos , Hipersensibilidade/enzimologia , Hipersensibilidade/imunologia , Hipersensibilidade/patologia , Imunoglobulina E/genética , Imunoglobulina E/imunologia , Masculino , Linhagem , Fosfoglucomutase/imunologia , Fosfoglucomutase/metabolismo , Células Th17/enzimologia , Células Th17/imunologia , Células Th17/patologia , Células Th2/enzimologia , Células Th2/imunologia , Células Th2/patologia , Adulto Jovem
2.
J Allergy Clin Immunol ; 131(6): 1624-34, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23541320

RESUMO

BACKGROUND: Impaired signaling in the IFN-γ/IL-12 pathway causes susceptibility to severe disseminated infections with mycobacteria and dimorphic yeasts. Dominant gain-of-function mutations in signal transducer and activator of transcription 1 (STAT1) have been associated with chronic mucocutaneous candidiasis. OBJECTIVE: We sought to identify the molecular defect in patients with disseminated dimorphic yeast infections. METHODS: PBMCs, EBV-transformed B cells, and transfected U3A cell lines were studied for IFN-γ/IL-12 pathway function. STAT1 was sequenced in probands and available relatives. Interferon-induced STAT1 phosphorylation, transcriptional responses, protein-protein interactions, target gene activation, and function were investigated. RESULTS: We identified 5 patients with disseminated Coccidioides immitis or Histoplasma capsulatum with heterozygous missense mutations in the STAT1 coiled-coil or DNA-binding domains. These are dominant gain-of-function mutations causing enhanced STAT1 phosphorylation, delayed dephosphorylation, enhanced DNA binding and transactivation, and enhanced interaction with protein inhibitor of activated STAT1. The mutations caused enhanced IFN-γ-induced gene expression, but we found impaired responses to IFN-γ restimulation. CONCLUSION: Gain-of-function mutations in STAT1 predispose to invasive, severe, disseminated dimorphic yeast infections, likely through aberrant regulation of IFN-γ-mediated inflammation.


Assuntos
Coccidioidomicose/genética , Histoplasmose/genética , Mutação , Fator de Transcrição STAT1/genética , Adolescente , Adulto , Linhagem Celular Transformada , Criança , Coccidioidomicose/diagnóstico , Coccidioidomicose/imunologia , Citocinas/biossíntese , Feminino , Regulação da Expressão Gênica , Histoplasmose/diagnóstico , Histoplasmose/imunologia , Humanos , Masculino , Fosforilação , Proteínas Inibidoras de STAT Ativados/metabolismo , Fator de Transcrição STAT1/metabolismo , Células Th17/imunologia , Ativação Transcricional , Adulto Jovem
3.
Am J Hum Genet ; 91(4): 713-20, 2012 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-23000145

RESUMO

Whole-exome sequencing was performed in a family affected by dominantly inherited inflammatory disease characterized by recurrent blistering skin lesions, bronchiolitis, arthralgia, ocular inflammation, enterocolitis, absence of autoantibodies, and mild immunodeficiency. Exome data from three samples, including the affected father and daughter and unaffected mother, were filtered for the exclusion of reported variants, along with benign variants, as determined by PolyPhen-2. A total of eight transcripts were identified as possible candidate genes. We confirmed a variant, c.2120C>A (p.Ser707Tyr), within PLCG2 as the only de novo variant that was present in two affected family members and not present in four unaffected members. PLCG2 encodes phospholipase Cγ2 (PLCγ2), an enzyme with a critical regulatory role in various immune and inflammatory pathways. The p.Ser707Tyr substitution is located in an autoinhibitory SH2 domain that is crucial for PLCγ2 activation. Overexpression of the altered p.Ser707Tyr protein and ex vivo experiments using affected individuals' leukocytes showed clearly enhanced PLCγ2 activity, suggesting increased intracellular signaling in the PLCγ2-mediated pathway. Recently, our laboratory identified in individuals with cold-induced urticaria and immune dysregulation PLCG2 exon-skipping mutations resulting in protein products with constitutive phospholipase activity but with reduced intracellular signaling at physiological temperatures. In contrast, the p.Ser707Tyr substitution in PLCγ2 causes a distinct inflammatory phenotype that is not provoked by cold temperatures and that has different end-organ involvement and increased intracellular signaling at physiological temperatures. Our results highlight the utility of exome-sequencing technology in finding causal mutations in nuclear families with dominantly inherited traits otherwise intractable by linkage analysis.


Assuntos
Doenças Hereditárias Autoinflamatórias/genética , Síndromes de Imunodeficiência/genética , Mutação de Sentido Incorreto , Fosfolipase C gama/genética , Exoma/genética , Éxons , Feminino , Ligação Genética , Predisposição Genética para Doença , Doenças Hereditárias Autoinflamatórias/enzimologia , Doenças Hereditárias Autoinflamatórias/metabolismo , Humanos , Síndromes de Imunodeficiência/enzimologia , Síndromes de Imunodeficiência/metabolismo , Leucócitos/metabolismo , Masculino , Domínios de Homologia de src/genética
4.
N Engl J Med ; 366(4): 330-8, 2012 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-22236196

RESUMO

BACKGROUND: Mendelian analysis of disorders of immune regulation can provide insight into molecular pathways associated with host defense and immune tolerance. METHODS: We identified three families with a dominantly inherited complex of cold-induced urticaria, antibody deficiency, and susceptibility to infection and autoimmunity. Immunophenotyping methods included flow cytometry, analysis of serum immunoglobulins and autoantibodies, lymphocyte stimulation, and enzymatic assays. Genetic studies included linkage analysis, targeted Sanger sequencing, and next-generation whole-genome sequencing. RESULTS: Cold urticaria occurred in all affected subjects. Other, variable manifestations included atopy, granulomatous rash, autoimmune thyroiditis, the presence of antinuclear antibodies, sinopulmonary infections, and common variable immunodeficiency. Levels of serum IgM and IgA and circulating natural killer cells and class-switched memory B cells were reduced. Linkage analysis showed a 7-Mb candidate interval on chromosome 16q in one family, overlapping by 3.5 Mb a disease-associated haplotype in a smaller family. This interval includes PLCG2, encoding phospholipase Cγ(2) (PLCγ(2)), a signaling molecule expressed in B cells, natural killer cells, and mast cells. Sequencing of complementary DNA revealed heterozygous transcripts lacking exon 19 in two families and lacking exons 20 through 22 in a third family. Genomic sequencing identified three distinct in-frame deletions that cosegregated with disease. These deletions, located within a region encoding an autoinhibitory domain, result in protein products with constitutive phospholipase activity. PLCG2-expressing cells had diminished cellular signaling at 37°C but enhanced signaling at subphysiologic temperatures. CONCLUSIONS: Genomic deletions in PLCG2 cause gain of PLCγ(2) function, leading to signaling abnormalities in multiple leukocyte subsets and a phenotype encompassing both excessive and deficient immune function. (Funded by the National Institutes of Health Intramural Research Programs and others.).


Assuntos
Doenças Autoimunes/genética , Síndromes Periódicas Associadas à Criopirina/genética , Síndromes de Imunodeficiência/genética , Fosfolipase C gama/genética , Deleção de Sequência , Temperatura Baixa/efeitos adversos , DNA Complementar/análise , DNA Complementar/isolamento & purificação , Feminino , Humanos , Masculino , Linhagem , Fenótipo , Fosfolipase C gama/metabolismo , Polimorfismo de Nucleotídeo Único , Análise de Sequência de DNA
5.
J Allergy Clin Immunol ; 127(2): 351-4, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21281865

RESUMO

Mounting evidence from animal models has demonstrated that alterations in T-cell receptor (TCR) signaling alone can lead to dramatically skewed differentiation of naive T cells into T(H)2 cells, to T(H)2 effector functions, and to T(H)2-related diseases. There is significant potential relevance of these observations to human disease. Specifically, a number of immunodeficiencies associated with atopic disease might have atopy as a manifestation because of aberrant TCR signaling. It is therefore important to attempt to identify a role for defects in TCR signaling in the pathogenesis of common atopic diseases.


Assuntos
Hipersensibilidade/etiologia , Receptores de Antígenos de Linfócitos T/fisiologia , Transdução de Sinais/fisiologia , Proteínas Adaptadoras de Transdução de Sinal/fisiologia , Animais , Fator de Transcrição GATA3/fisiologia , Humanos , Hipersensibilidade/imunologia , Imunofenotipagem , Proteínas de Membrana/fisiologia , Linfócitos T Reguladores/fisiologia , Células Th2/imunologia
6.
Trends Immunol ; 30(9): 430-8, 2009 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-19699149

RESUMO

Defects in T cell homeostatic mechanisms can result in T cell lymphopenia, defined as decreased numbers of lymphocytes. Lymphopenia results in homeostatic proliferation in order to maintain T cell homeostasis. It has been proposed that homeostatic proliferation can expand the pool of autoreactive T cells that promote autoimmunity, and indeed recent studies have further substantiated this observation in both animal models and humans. Conversely, homeostatic proliferation can promote tumor immunity by allowing tumor-specific T cells to accumulate. In this review, we discuss how the outcome of homeostatic proliferation can function both in a deleterious manner in autoimmunity and a beneficial way in tumor immunity. We also discuss the roles of various cytokines and T regulatory cells that control homeostatic proliferation.


Assuntos
Doenças do Sistema Imunitário/imunologia , Linfócitos T Reguladores/metabolismo , Linfócitos T/patologia , Animais , Autoimunidade , Proliferação de Células , Citocinas/imunologia , Homeostase , Humanos , Doenças do Sistema Imunitário/patologia , Vigilância Imunológica , Linfócitos T/imunologia , Linfócitos T/metabolismo , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/patologia
7.
PLoS One ; 3(9): e3118, 2008 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-18773086

RESUMO

BACKGROUND: IL-21, a member of the common gamma-chain utilizing family of cytokines, participates in immune and inflammatory processes. In addition, the cytokine has been linked to autoimmunity in humans and rodents. METHODOLOGY/PRINCIPAL FINDINGS: To investigate the mechanism whereby IL-21 affects the immune system, we investigated its role in T cell homeostasis and autoimmunity in both non-autoimmune C57BL/6 and autoimmune NOD mice. Our data indicate that IL-21R knockout C57BL/6 and NOD mice show increased size of their lymphocyte population and decreased homeostatic proliferation. In addition, our experimental results demonstrate that IL-21 inhibits T cell survival. These data suggest that IL-21 acts to limit the size of the T cell pool. Furthermore, our data suggest IL-21 may contribute to the development of autoimmunity. CONCLUSIONS/SIGNIFICANCE: Taken together, our results suggest that IL-21 plays a global role in regulating T cell homeostasis, promoting the continuous adaptation of the T cell lymphoid space.


Assuntos
Regulação da Expressão Gênica , Interleucinas/fisiologia , Linfócitos T/metabolismo , Linfócitos T/fisiologia , Animais , Antígenos/química , Autoimunidade , Proliferação de Células , Homeostase , Humanos , Interleucinas/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos NOD , Camundongos Knockout , Modelos Biológicos , Receptores de Interleucina-21/genética
8.
J Biol Chem ; 283(23): 15628-37, 2008 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-18413311

RESUMO

Mice were subjected to different dietary manipulations to selectively alter expression of hepatic sterol regulatory element-binding protein 1 (SREBP-1) or SREBP-2. mRNA levels for key target genes were measured and compared with the direct binding of SREBP-1 and -2 to the associated promoters using isoform specific antibodies in chromatin immunoprecipitation studies. A diet supplemented with Zetia (ezetimibe) and lovastatin increased and decreased nuclear SREBP-2 and SREBP-1, respectively, whereas a fasting/refeeding protocol dramatically altered SREBP-1 but had modest effects on SREBP-2 levels. Binding of both SREBP-1 and -2 increased on promoters for 3-hydroxy-3-methylglutaryl-CoA reductase, fatty-acid synthase, and squalene synthase in livers of Zetia/lovastatin-treated mice despite the decline in total SREBP-1 protein. In contrast, only SREBP-2 binding was increased for the low density lipoprotein receptor promoter. Decreased SREBP-1 binding during fasting and a dramatic increase upon refeeding indicates that the lipogenic "overshoot" for fatty-acid synthase gene expression known to occur during high carbohydrate refeeding can be attributed to a similar overshoot in SREBP-1 binding. SREBP co-regulatory protein recruitment was also increased/decreased in parallel with associated changes in SREBP binding, and there were clear distinctions for different promoters in response to the dietary manipulations. Taken together, these studies reveal that there are alternative molecular mechanisms for activating SREBP target genes in response to the different dietary challenges of Zetia/lovastatin versus fasting/refeeding. This underscores the mechanistic flexibility that has evolved at the individual gene/promoter level to maintain metabolic homeostasis in response to shifting nutritional states and environmental fluctuations.


Assuntos
Regulação Enzimológica da Expressão Gênica/fisiologia , Metabolismo dos Lipídeos/fisiologia , Fígado/enzimologia , Elementos de Resposta/fisiologia , Proteína de Ligação a Elemento Regulador de Esterol 1/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 2/metabolismo , Animais , Anticolesterolemiantes , Azetidinas/farmacologia , Suplementos Nutricionais , Ezetimiba , Farnesil-Difosfato Farnesiltransferase/biossíntese , Jejum/metabolismo , Ácido Graxo Sintases/biossíntese , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Homeostase/efeitos dos fármacos , Homeostase/fisiologia , Hidroximetilglutaril-CoA Redutases/biossíntese , Metabolismo dos Lipídeos/efeitos dos fármacos , Lovastatina/farmacologia , Masculino , Camundongos , RNA Mensageiro/metabolismo
9.
J Biol Chem ; 281(2): 807-12, 2006 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-16282330

RESUMO

Cholesterol homeostasis in mammals involves pathways for biosynthesis, cellular uptake, and hepatic conversion to bile acids. Key genes for all three pathways are regulated by negative feedback control. Uptake and biosynthesis are directly regulated by cholesterol through its inhibition of the proteolytic activation of the sterol regulatory element binding proteins. The conversion of cholesterol into bile acids in the liver is regulated through the bile acid-dependent induction of the negatively acting small heterodimer partner nuclear receptor. In this report, we have shown that the small heterodimer partner also directly regulates cholesterol biosynthesis through inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase but has no effect on low density lipoprotein receptor expression. This has significant metabolic significance, as it provides both a mechanism to independently regulate cholesterol synthesis from uptake (an essential regulatory feature known to occur in vivo) and a pathway for direct regulation of cholesterol biosynthesis by bile acids. This latter feature ensures that the early phase of bile acid synthesis (pre-cholesterol) is in metabolic communication with the later stages of the pathway to properly regulate whole pathway flux. This highlights an important regulatory feature that is shared with other key branched, multienzyme pathways, such as glycolysis, where pathway outflow through pyruvate kinase is regulated by the concentration of a key early intermediate, fructose 1,6-bisphosphate.


Assuntos
Proteínas de Ligação a DNA/genética , Regulação Enzimológica da Expressão Gênica , Hidroximetilglutaril-CoA-Redutases NADP-Dependentes/genética , Regiões Promotoras Genéticas , Receptores Citoplasmáticos e Nucleares/genética , Fatores de Transcrição/genética , Animais , Linhagem Celular , Colesterol/química , Colesterol/metabolismo , Ácido Cólico/química , Cromatina/química , Imunoprecipitação da Cromatina , DNA/química , Dimerização , Frutosedifosfatos/química , Deleção de Genes , Humanos , Hidroximetilglutaril-CoA-Redutases NADP-Dependentes/química , Immunoblotting , Camundongos , Camundongos Transgênicos , Modelos Biológicos , Mutação , Ligação Proteica , Estrutura Terciária de Proteína , RNA/química , Receptores de LDL/química , Proteínas Recombinantes/química
10.
Mol Cell Biol ; 25(8): 2946-56, 2005 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15798184

RESUMO

Sterol regulatory element-binding proteins (SREBPs) are a subfamily of basic helix-loop-helix-leucine zipper proteins that regulate lipid metabolism. We show novel evidence of the in vivo occurrence and subnuclear spatial localization of both exogenously expressed SREBP-1a and -2 homodimers and heterodimers obtained by two-photon imaging and spectroscopy fluorescence resonance energy transfer. SREBP-1a homodimers localize diffusely in the nucleus, whereas SREBP-2 homodimers and the SREBP-1a/SREBP-2 heterodimer localize predominantly to nuclear speckles or foci, with some cells showing a diffuse pattern. We also used tethered SREBP dimers to demonstrate that both homo- and heterodimeric SREBPs activate transcription in vivo. Ultrastructural analysis revealed that the punctate foci containing SREBP-2 are electron-dense nuclear bodies, similar or identical to structures containing the promyelocyte (PML) protein. Immunofluorescence studies suggest that a dynamic interplay exists between PML, as well as another component of the PML-containing nuclear body, SUMO-1, and SREBP-2 within these nuclear structures. These findings provide new insight into the overall process of transcriptional activation mediated by the SREBP family.


Assuntos
Proteínas Estimuladoras de Ligação a CCAAT/análise , Proteínas Estimuladoras de Ligação a CCAAT/fisiologia , Núcleo Celular/química , Proteínas de Ligação a DNA/análise , Proteínas de Ligação a DNA/fisiologia , Fatores de Transcrição/análise , Fatores de Transcrição/fisiologia , Ativação Transcricional , Proteínas Estimuladoras de Ligação a CCAAT/genética , Linhagem Celular , Núcleo Celular/metabolismo , Núcleo Celular/ultraestrutura , Proteínas de Ligação a DNA/genética , Dimerização , Transferência Ressonante de Energia de Fluorescência , Genes Reporter/genética , Humanos , Metabolismo dos Lipídeos , Luciferases/análise , Luciferases/genética , Proteínas de Neoplasias/análise , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/análise , Proteínas Nucleares/metabolismo , Fótons , Regiões Promotoras Genéticas/genética , Proteína da Leucemia Promielocítica , Estrutura Terciária de Proteína , Receptores de LDL/genética , Proteína SUMO-1/análise , Proteína SUMO-1/metabolismo , Deleção de Sequência , Proteína de Ligação a Elemento Regulador de Esterol 1 , Proteína de Ligação a Elemento Regulador de Esterol 2 , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Genética , Proteínas Supressoras de Tumor
11.
J Biol Chem ; 280(5): 3338-45, 2005 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-15550381

RESUMO

Sterol regulatory element-binding proteins (SREBPs) are basic helix-loop-helix leucine zipper proteins that act as dimers to activate genes in lipid metabolism. Three SREBP isoforms, 1a, 1c, and 2, are expressed at varying levels in different tissues. Thus, homo- and heterodimers probably contribute to overall SREBP activity. No studies have directly evaluated the formation or activation properties of SREBP homo- and heterodimers. Studies with overexpressed SREBP monomers are inconclusive regarding the function of a particular SREBP dimer because of potential dimerization with endogenous proteins. To assess activation by a particular SREBP dimer, we fused DNA encoding individual monomers together via a predicted flexible polypeptide tether. Tethered SREBP dimers bound DNA equivalently to the monomeric proteins and were resistant to dominant negative SREBP-1 inhibition, confirming preferential formation of intramolecular dimers. Tethered SREBP-1a and -2 homodimers, similar to the monomeric forms, activated target genes more robustly than tethered SREBP-1c homodimers. A forced SREBP-1a/2 heterodimer had similar activity to the respective homodimers. However, SREBP-1c in a heterodimer with either SREBP-1a or -2 attenuated the activity relative to the SREBP-1a or -2 homodimers. These experiments provide some of the first data showing that the integrity of both activation domains in a dimeric transcription factor is required for maximal activity. In addition, the results support a model where changes in SREBP-1c protein expression that occur in response to insulin signaling and liver X receptor signaling would be predicted to increase or decrease overall SREBP activity in a tissue-specific fashion depending on the initial fractional contribution of SREBP-1c to total cellular levels of SREBP.


Assuntos
Proteínas Estimuladoras de Ligação a CCAAT/química , Proteínas Estimuladoras de Ligação a CCAAT/genética , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Fatores de Transcrição/química , Fatores de Transcrição/genética , Ativação Transcricional/fisiologia , Sítios de Ligação , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Linhagem Celular Transformada , Proteínas de Ligação a DNA/metabolismo , Dimerização , Regulação da Expressão Gênica/fisiologia , Humanos , Isomerismo , Regiões Promotoras Genéticas/fisiologia , Estrutura Terciária de Proteína , Proteína de Ligação a Elemento Regulador de Esterol 1 , Fatores de Transcrição/metabolismo
12.
Mol Cell Biol ; 24(18): 8288-300, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15340088

RESUMO

Requisite levels of intracellular cholesterol and fatty acids are maintained in part by the sterol regulatory element binding proteins (SREBPs). Three major SREBP isoforms exist; SREBP-1a and SREBP-1c are expressed from overlapping mRNAs, whereas SREBP-2 is encoded by a separate gene. The active forms of SREBP-1a and SREBP-1c differ only at their extreme N termini; SREBP-1c lacks 28 aa present in SREBP-1a and instead contains 4 unique aa of its own. While the SREBP-1a and -1c isoforms differentially activate transcription, the molecular basis of this difference is unknown. Here we define the differences between these proteins that confer the enhanced activity of SREBP-1a and demonstrate that this enhancement is a direct result of its avid binding to the coactivator CREB binding protein (CBP) and the mammalian mediator complex. While previous work determined that the C/H1 zinc finger and KIX domains of CBP bind to SREBP-1a, we provide evidence that the interaction with C/H1 is important for gene activation. We further show that the association between the activation domain of SREBP-1 and mediator is through aa 500 to 824 of DRIP150. Finally, we demonstrate the recruitment of mediator to an SREBP-responsive promoter in a sterol-dependent manner.


Assuntos
Proteínas Estimuladoras de Ligação a CCAAT/genética , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Regulação da Expressão Gênica , Fatores de Transcrição , Sequência de Aminoácidos , Sítios de Ligação , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Linhagem Celular , Corticosterona , Humanos , Dados de Sequência Molecular , Mutagênese , Regiões Promotoras Genéticas , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Homologia de Sequência de Aminoácidos , Proteína de Ligação a Elemento Regulador de Esterol 1 , Esteróis/metabolismo , Transativadores/genética , Transativadores/metabolismo , Ativação Transcricional
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