Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
Mais filtros

Base de dados
Tipo de documento
País de afiliação
Intervalo de ano de publicação
1.
Cancer Cell ; 12(5): 457-66, 2007 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17996649

RESUMO

Hematopoietic transcription factors are involved in chromosomal translocations, which generate fusion proteins contributing to leukemia pathogenesis. Analysis of patient's primary leukemia blasts revealed that those carrying the t(8;21) generating AML1/ETO, the most common acute myeloid leukemia-associated fusion protein, display low levels of a microRNA-223 (miR-223), a regulator of myelopoiesis. Here, we show that miR-223 is a direct transcriptional target of AML1/ETO. By recruiting chromatin remodeling enzymes at an AML1-binding site on the pre-miR-223 gene, AML1/ETO induces heterochromatic silencing of miR-223. Ectopic miR-223 expression, RNAi against AML1/ETO, or demethylating treatment enhances miR-223 levels and restores cell differentiation. Here, we identify an additional action for a leukemia fusion protein linking the epigenetic silencing of a microRNA locus to the differentiation block of leukemia.


Assuntos
Subunidade alfa 2 de Fator de Ligação ao Core/genética , Subunidade alfa 2 de Fator de Ligação ao Core/fisiologia , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/fisiologia , Epigênese Genética , Regulação Leucêmica da Expressão Gênica , Inativação Gênica , Leucemia/genética , MicroRNAs/genética , Proteínas Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/fisiologia , RNA Mensageiro/fisiologia , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologia , Linhagem Celular Tumoral , Células HL-60 , Humanos , Cariotipagem , MicroRNAs/fisiologia , Modelos Biológicos , Mielopoese , Proteína 1 Parceira de Translocação de RUNX1 , Ativação Transcricional
2.
Blood ; 119(17): 4034-46, 2012 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-22327224

RESUMO

Epigenetic modifications regulate developmental genes involved in stem cell identity and lineage choice. NFI-A is a posttranscriptional microRNA-223 (miR-223) target directing human hematopoietic progenitor lineage decision: NFI-A induction or silencing boosts erythropoiesis or granulopoiesis, respectively. Here we show that NFI-A promoter silencing, which allows granulopoiesis, is guaranteed by epigenetic events, including the resolution of opposing chromatin "bivalent domains," hypermethylation, recruitment of polycomb (PcG)-RNAi complexes, and miR-223 promoter targeting activity. During granulopoiesis, miR-223 localizes inside the nucleus and targets the NFI-A promoter region containing PcGs binding sites and miR-223 complementary DNA sequences, evolutionarily conserved in mammalians. Remarkably, both the integrity of the PcGs-RNAi complex and DNA sequences matching the seed region of miR-223 are required to induce NFI-A transcriptional silencing. Moreover, ectopic miR-223 expression in human myeloid progenitors causes heterochromatic repression of NFI-A gene and channels granulopoiesis, whereas its stable knockdown produces the opposite effects. Our findings indicate that, besides the regulation of translation of mRNA targets, endogenous miRs can affect gene expression at the transcriptional level, functioning in a critical interface between chromatin remodeling complexes and the genome to direct fate lineage determination of hematopoietic progenitors.


Assuntos
Regulação da Expressão Gênica , Granulócitos/citologia , MicroRNAs/genética , Fatores de Transcrição NFI/genética , Regiões Promotoras Genéticas/genética , Proteínas Repressoras/metabolismo , Transcrição Gênica , Sequência de Bases , Western Blotting , Imunoprecipitação da Cromatina , Epigenômica , Citometria de Fluxo , Inativação Gênica , Hematopoese/fisiologia , Heterocromatina/genética , Humanos , Imunoprecipitação , Leucemia/genética , Leucemia/metabolismo , Leucemia/patologia , Luciferases/metabolismo , MicroRNAs/metabolismo , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Mielopoese/fisiologia , Fatores de Transcrição NFI/antagonistas & inibidores , Fatores de Transcrição NFI/metabolismo , Proteínas do Grupo Polycomb , RNA Mensageiro/genética , RNA Interferente Pequeno/genética , Reação em Cadeia da Polimerase em Tempo Real , Homologia de Sequência do Ácido Nucleico
3.
Nat Cell Biol ; 9(7): 775-87, 2007 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-17589498

RESUMO

We investigated the role of microRNAs (miRNA) 17-5p, 20a and 106a in monocytic differentiation and maturation. In unilineage monocytic culture generated by haematopoietic progenitor cells these miRNAs are downregulated, whereas the transcription factor acute myeloid leukaemia-1 (AML1; also known as Runt-related transcription factor 1, Runx1) is upregulated at protein but not mRNA level. As miRNAs 17-5p, 20a and 106a bind the AML1 mRNA 3'UTR, their decline may unblock AML1 translation. Accordingly, transfection with miRNA 17-5p-20a-106a suppresses AML1 protein expression, leading to M-CSF receptor (M-CSFR) downregulation, enhanced blast proliferation and inhibition of monocytic differentiation and maturation. Treatment with anti-miRNA 17-5p, 20a and 106a causes opposite effects. Knockdown of AML1 or M-CSFR by short interfering RNA (siRNA) mimics the action of the miRNA 17-5p-20a-106a, confirming that these miRNAs target AML1, which promotes M-CSFR transcription. In addition, AML1 binds the miRNA 17-5p-92 and 106a-92 cluster promoters and transcriptionally inhibits the expression of miRNA 17-5p-20a-106a. These studies indicate that monocytopoiesis is controlled by a circuitry involving sequentially miRNA 17-5p-20a-106a, AML1 and M-CSFR, whereby miRNA 17-5p-20a-106a function as a master gene complex interlinked with AML1 in a mutual negative feedback loop.


Assuntos
Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Células-Tronco Hematopoéticas/citologia , MicroRNAs/fisiologia , Monócitos/citologia , Receptor de Fator Estimulador de Colônias de Macrófagos/biossíntese , Regulação para Cima , Diferenciação Celular/fisiologia , Células Cultivadas , Retroalimentação Fisiológica , Feminino , Células-Tronco Hematopoéticas/fisiologia , Humanos , Monócitos/metabolismo , Regiões Promotoras Genéticas , RNA Interferente Pequeno/metabolismo
4.
J Biol Chem ; 286(31): 27092-102, 2011 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-21659508

RESUMO

Polyunsaturated fatty acids (PUFAs) inhibit proliferation and induce differentiation in leukemia cells. To investigate the molecular mechanisms whereby fatty acids affect these processes, U937 leukemia cells were conditioned with stearic, oleic, linolenic, α-linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic acids. PUFAs affected proliferation; eicosapentaenoic acid (EPA) was the most potent on cell cycle progression. EPA enhanced the expression of the myeloid lineage-specific transcription factors CCAAT/enhancer-binding proteins (C/EBPß and C/EBPδ), PU.1, and c-Jun, resulting in increased expression of the monocyte lineage-specific target gene, the macrophage colony-stimulating factor receptor. Indeed, it is known that PU.1 and C/EBPs interact with their consensus sequences on a small DNA fragment of macrophage colony-stimulating factor receptor promoter, which is a determinant for expression. We demonstrated that C/EBPß and C/EBPδ bind the same response element as a heterodimer. We focused on the enhanced expression of C/EBPδ, which has been reported to be a tumor suppressor gene silenced by promoter hypermethylation in U937 cells. After U937 conditioning with EPA and bisulfite sequencing of the -370/-20 CpG island on the C/EBPδ promoter region, we found a site-specific CpG demethylation that was a determinant for the binding activity of Sp1, an essential factor for C/EBPδ gene basal expression. Our results provide evidence for a new role of PUFAs in the regulation of gene expression. Moreover, we demonstrated for the first time that re-expression of the tumor suppressor C/EBPδ is controlled by the methylation state of a site-specific CpG dinucleotide.


Assuntos
Proteína delta de Ligação ao Facilitador CCAAT/metabolismo , Ilhas de CpG , Metilação de DNA/efeitos dos fármacos , Ácido Eicosapentaenoico/farmacologia , Oncogenes , Sequência de Bases , Proteína delta de Ligação ao Facilitador CCAAT/genética , Imunoprecipitação da Cromatina , Primers do DNA , Ensaio de Desvio de Mobilidade Eletroforética , Citometria de Fluxo , Humanos , Reação em Cadeia da Polimerase , Células U937
5.
J Clin Med ; 8(2)2019 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-30678026

RESUMO

Non-small cell lung cancer (NSCLC) is the primary cause of cancer-related death worldwide, with a low 5-year survival rate even in fully resected early-stage disease. Novel biomarkers to identify patients at higher risk of relapse are needed. We studied the prognostic value of 84 circulating microRNAs (miRNAs) in 182 patients with resected early-stage NSCLC (99 adenocarcinoma (ADC), 83 squamous cell carcinoma (SCC)) from whom peripheral blood samples were collected pre-surgery. miRNA expression was analyzed in relation to disease-free survival (DFS) and overall survival (OS). In univariable analyses, five miRNAs (miR-26a-5p, miR-126-3p, miR-130b-3p, miR-205-5p, and miR-21-5p) were significantly associated with DFS in SCC, and four (miR-130b-3p, miR-26a-5p, miR-126-3p, and miR-205-5p) remained significantly associated with OS. In ADC, miR-222-3p, miR-22-3p, and mir-93-5p were significantly associated with DFS, miR-22-3p remaining significant for OS. Given the high-dimensionality of the dataset, multivariable models were obtained using a regularized Cox regression including all miRNAs and clinical covariates. After adjustment for disease stage, only miR-126-3p showed an independent prognostic role, with higher values associated with longer DFS in SCC patients. With regard to ADC and OS, no miRNA remained significant in multivariable analysis. Further investigation into the role of miR-126 as a prognostic marker in early-stage NSCLC is warranted.

6.
PLoS One ; 9(1): e85025, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24454781

RESUMO

Epigenetic alterations, including aberrant DNA methylation, contribute to tumor development and progression. Silencing of tumor suppressor genes may be ascribed to promoter DNA hypermethylation, a reversible phenomenon intensely investigated as potential therapeutic target. Previously, we demonstrated that eicosapentaenoic acid (EPA) exhibits a DNA demethylating action that promotes the re-expression of the tumor suppressor gene CCAAT/enhancer-binding protein δ (C/EBPδ). The C/EBPß/C/EBPδ heterodimer formed appears essential for the monocyte differentiation commitment. The present study aims to evaluate the effect of EPA on RAS/extracellular signal regulated kinases (ERK1/2)/C/EBPß pathway, known to be induced during the monocyte differentiation program. We found that EPA conditioning of U937 leukemia cells activated RAS/ERK/C/EBPß pathway, increasing the C/EBPß and ERK1/2 active phosphorylated forms. Transcriptional induction of the upstream activator H-Ras gene resulted in increased expression of H-Ras protein in the active pool of non raft membrane fraction. H-Ras gene analysis identified an hypermethylated CpG island in intron 1 that can affect the DNA-protein interaction modifying RNA polymerase II (RNAPII) activity. EPA treatment demethylated almost completely this CpG island, which was associated with an enrichment of active RNAPII. The increased binding of the H-Ras transcriptional regulator p53 to its consensus sequence within the intronic CpG island further confirmed the effect of EPA as demethylating agent. Our results provide the first evidence that an endogenous polyunsaturated fatty acid (PUFA) promotes a DNA demethylation process responsible for the activation of RAS/ERK/C/EBPß pathway during the monocyte differentiation commitment. The new role of EPA as demethylating agent paves the way for studying PUFA action when aberrant DNA methylation is involved.


Assuntos
Proteína delta de Ligação ao Facilitador CCAAT/metabolismo , Ilhas de CpG/genética , Metilação de DNA/genética , Ácido Eicosapentaenoico/farmacologia , Íntrons/genética , Leucemia/genética , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Proteínas Proto-Oncogênicas p21(ras)/genética , Azacitidina/farmacologia , Sequência de Bases , Metilação de DNA/efeitos dos fármacos , Éxons/genética , Humanos , Leucemia/patologia , Sistema de Sinalização das MAP Quinases/genética , Microdomínios da Membrana/efeitos dos fármacos , Microdomínios da Membrana/metabolismo , Dados de Sequência Molecular , Fosforilação/efeitos dos fármacos , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/genética , Isoformas de Proteínas/metabolismo , RNA Polimerase II/metabolismo , Transcrição Gênica/efeitos dos fármacos , Proteína Supressora de Tumor p53/metabolismo , Células U937
7.
Cell Cycle ; 11(19): 3543-9, 2012 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-22895111

RESUMO

Advances in the understanding of the epigenetic events underlying the regulation of developmental genes expression and cell lineage commitment are revealing novel regulatory networks. These also involve distinct components of the epigenetic pathways, including chromatin histone modification, DNA methylation, repression by polycomb complexes and microRNAs. Changes in chromatin structure, DNA methylation status and microRNA expression levels represent flexible, reversible and heritable mechanisms for the maintenance of stem cell states and cell fate decisions. We recently provided novel evidence showing that microRNAs, besides determining the post-transcriptional gene silencing of their targets, also bind to evolutionarily conserved complementary genomic seed-matches present on target gene promoters. At these sites, microRNAs can function as a critical interface between chromatin remodeling complexes and the genome for transcriptional gene silencing. Here, we discuss our novel findings supporting a role of the transcriptional chromatin targeting by polycomb-microRNA complexes in lineage fate determination of human hematopoietic cells.


Assuntos
Linhagem da Célula/genética , MicroRNAs/metabolismo , Proteínas do Grupo Polycomb/metabolismo , Transcrição Gênica , Sequência de Bases , Cromatina/metabolismo , Epigênese Genética , Evolução Molecular , Hematopoese/genética , Humanos , Modelos Genéticos , Regiões Promotoras Genéticas/genética
8.
EMBO J ; 24(6): 1232-42, 2005 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-15729358

RESUMO

The AML1/ETO and PML/RARalpha leukemia fusion proteins induce acute myeloid leukemia by acting as transcriptional repressors. They interact with corepressors, such as N-CoR and SMRT, that recruit a multiprotein complex containing histone deacetylases on crucial myeloid differentiation genes. This leads to gene repression contributing to generate a differentiation block. We expressed in leukemia cells containing PML/RARalpha and AML1/ETO N-CoR protein fragments derived from fusion protein/corepressor interaction surfaces. This blocks N-CoR/SMRT binding by these fusion proteins, and disrupts the repressor protein complex. In consequence, the expression of genes repressed by these fusion proteins increases and differentiation response to vitamin D3 and retinoic acid is restored in previously resistant cells. The alteration of PML/RARalpha-N-CoR/SMRT connections triggers proteasomal degradation of the fusion protein. The N-CoR fragments are biologically effective also when directly transduced by virtue of a protein transduction domain. Our data indicate that fusion protein activity is permanently required to maintain the leukemia phenotype and show the route to developing a novel therapeutic approach for leukemia, based on its molecular pathogenesis.


Assuntos
Proteínas de Ligação a DNA/metabolismo , Leucemia Mieloide/metabolismo , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/metabolismo , Proteínas de Fusão Oncogênica/metabolismo , Proteínas Repressoras/metabolismo , Fatores de Transcrição/metabolismo , Doença Aguda , Diferenciação Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Colecalciferol/farmacologia , Subunidade alfa 2 de Fator de Ligação ao Core , Proteínas de Ligação a DNA/antagonistas & inibidores , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Proteínas de Neoplasias/genética , Proteínas Nucleares/antagonistas & inibidores , Correpressor 1 de Receptor Nuclear , Correpressor 2 de Receptor Nuclear , Proteínas de Fusão Oncogênica/genética , Peptídeos/genética , Peptídeos/fisiologia , Estrutura Terciária de Proteína/genética , Estrutura Terciária de Proteína/fisiologia , Proteína 1 Parceira de Translocação de RUNX1 , Proteínas Repressoras/antagonistas & inibidores , Fatores de Transcrição/genética , Tretinoína/farmacologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA