RESUMEN
Epigenetics, the modification of chromatin without changing the DNA sequence itself, determines whether a gene is expressed, and how much of a gene is expressed. Methylation of lysine 27 on histone 3 (H3K27me), a modification usually associated with gene repression, has established roles in regulating the expression of genes involved in lineage commitment and differentiation. Not surprisingly, alterations in the homeostasis of this critical mark have emerged as a recurrent theme in the pathogenesis of many cancers. Perturbations in the distribution or levels of H3K27me occur due to deregulation at all levels of the process, either by mutation in the histone itself, or changes in the activity of the writers, erasers, or readers of this mark. Additionally, as no single histone mark alone determines the overall transcriptional readiness of a chromatin region, deregulation of other chromatin marks can also have dramatic consequences. Finally, the significance of mutations altering H3K27me is highlighted by the poor clinical outcome of patients whose tumors harbor such lesions. Current therapeutic approaches targeting aberrant H3K27 methylation remain to be proven useful in the clinic. Understanding the biological consequences and gene expression pathways affected by aberrant H3K27 methylation may lead to identification of new therapeutic targets and strategies.
Asunto(s)
Metilación de ADN , Epigénesis Genética/genética , Regulación Neoplásica de la Expresión Génica , Histonas/metabolismo , Neoplasias/genética , Factores de Transcripción/metabolismo , Animales , Histonas/genética , Humanos , LisinaRESUMEN
MMSET/WHSC1 is a histone methyltransferase (HMT) overexpressed in t(4;14)+ multiple myeloma (MM) patients, believed to be the driving factor in the pathogenesis of this MM subtype. MMSET overexpression in MM leads to an increase in histone 3 lysine 36 dimethylation (H3K36me2), and a decrease in histone 3 lysine 27 trimethylation (H3K27me3), as well as changes in proliferation, gene expression and chromatin accessibility. Prior work linked methylation of histones to the ability of cells to undergo DNA damage repair. In addition, t(4;14)+ patients frequently relapse after regimens that include DNA damage-inducing agents, suggesting that MMSET may play a role in DNA damage repair and response. In U2OS cells, we found that MMSET is required for efficient non-homologous end joining as well as homologous recombination. Loss of MMSET led to loss of expression of several DNA repair proteins, as well as decreased recruitment of DNA repair proteins to sites of DNA double-strand breaks (DSBs). By using genetically matched MM cell lines that had either high (pathological) or low (physiological) expression of MMSET, we found that MMSET-high cells had increased damage at baseline. Upon addition of a DNA-damaging agent, MMSET-high cells repaired DNA damage at an enhanced rate and continued to proliferate, whereas MMSET-low cells accumulated DNA damage and entered cell cycle arrest. In a murine xenograft model using t(4;14)+ KMS11 MM cells harboring an inducible MMSET shRNA, depletion of MMSET enhanced the efficacy of chemotherapy, inhibiting tumor growth and extending survival. These findings help explain the poorer prognosis of t(4;14) MM and further validate MMSET as a potential therapeutic target in MM and other cancers.
Asunto(s)
Antineoplásicos/farmacología , Daño del ADN , Reparación del ADN , Resistencia a Antineoplásicos , N-Metiltransferasa de Histona-Lisina/metabolismo , Proteínas Represoras/metabolismo , Animales , Línea Celular Tumoral , Proliferación Celular , Ensamble y Desensamble de Cromatina/efectos de los fármacos , Daño del ADN/efectos de los fármacos , Modelos Animales de Enfermedad , Resistencia a Antineoplásicos/genética , N-Metiltransferasa de Histona-Lisina/genética , Humanos , Ratones , Neoplasias/tratamiento farmacológico , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/patología , Pronóstico , Unión Proteica , Interferencia de ARN , ARN Interferente Pequeño/genética , Proteínas Represoras/genética , Transducción de Señal , Carga Tumoral , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Epigenetic deregulation of gene expression has a role in the initiation and progression of prostate cancer (PCa). The histone methyltransferase MMSET/WHSC1 (Multiple Myeloma SET domain) is overexpressed in a number of metastatic tumors, but its mechanism of action has not been defined. In this work, we found that PCa cell lines expressed significantly higher levels of MMSET compared with immortalized, non-transformed prostate cells. Knockdown experiments showed that, in metastatic PCa cell lines, dimethylation of lysine 36 and trimethylation of lysine 27 on histone H3 (H3K36me2 and H3K27me3, respectively) depended on MMSET expression, whereas depletion of MMSET in benign prostatic cells did not affect chromatin modifications. Knockdown of MMSET in DU145 and PC-3 tumor cells decreased cell proliferation, colony formation in soft agar and strikingly diminished cell migration and invasion. Conversely, overexpression of MMSET in immortalized, non-transformed RWPE-1 cells promoted cell migration and invasion, accompanied by an epithelial-mesenchymal transition (EMT). Among a panel of EMT-promoting genes analyzed, TWIST1 expression was strongly activated in response to MMSET. Chromatin immunoprecipitation analysis demonstrated that MMSET binds to the TWIST1 locus and leads to an increase in H3K36me2, suggesting a direct role of MMSET in the regulation of this gene. Depletion of TWIST1 in MMSET-overexpressing RWPE-1 cells blocked cell invasion and EMT, indicating that TWIST1 was a critical target of MMSET, responsible for the acquisition of an invasive phenotype. Collectively, these data suggest that MMSET has a role in PCa pathogenesis and progression through epigenetic regulation of metastasis-related genes.
Asunto(s)
Transición Epitelial-Mesenquimal , N-Metiltransferasa de Histona-Lisina/metabolismo , Proteínas Nucleares/metabolismo , Neoplasias de la Próstata/enzimología , Proteínas Represoras/metabolismo , Proteína 1 Relacionada con Twist/metabolismo , Línea Celular Tumoral , Movimiento Celular , Epigénesis Genética , Expresión Génica , Regulación Neoplásica de la Expresión Génica , Técnicas de Silenciamiento del Gen , N-Metiltransferasa de Histona-Lisina/genética , Histonas/metabolismo , Humanos , Masculino , Metilación , Invasividad Neoplásica , Proteínas Nucleares/genética , Neoplasias de la Próstata/patología , Unión Proteica , Procesamiento Proteico-Postraduccional , ARN Interferente Pequeño/genética , Proteínas Represoras/genética , Proteína 1 Relacionada con Twist/genéticaRESUMEN
Multiple myeloma (MM) represents the malignant proliferation of terminally differentiated B cells, which, in many cases, is associated with the maintenance of high levels of the oncoprotein c-MYC. Overexpression of the histone methyltransferase MMSET (WHSC1/NSD2), due to t(4;14) chromosomal translocation, promotes the proliferation of MM cells along with global changes in chromatin; nevertheless, the precise mechanisms by which MMSET stimulates neoplasia remain incompletely understood. We found that MMSET enhances the proliferation of MM cells by stimulating the expression of c-MYC at the post-transcriptional level. A microRNA (miRNA) profiling experiment in t(4;14) MM cells identified miR-126* as an MMSET-regulated miRNA predicted to target c-MYC mRNA. We show that miR-126* specifically targets the 3'-untranslated region (3'-UTR) of c-MYC, inhibiting its translation and leading to decreased c-MYC protein levels. Moreover, the expression of this miRNA was sufficient to decrease the proliferation rate of t(4;14) MM cells. Chromatin immunoprecipitation analysis showed that MMSET binds to the miR-126* promoter along with the KAP1 corepressor and histone deacetylases, and is associated with heterochromatic modifications, characterized by increased trimethylation of H3K9 and decreased H3 acetylation, leading to miR-126* repression. Collectively, this study shows a novel mechanism that leads to increased c-MYC levels and enhanced proliferation of t(4;14) MM, and potentially other cancers with high MMSET expression.
Asunto(s)
Proliferación Celular , Regulación Neoplásica de la Expresión Génica , N-Metiltransferasa de Histona-Lisina/metabolismo , MicroARNs/genética , Mieloma Múltiple/patología , Proteínas Proto-Oncogénicas c-myc/metabolismo , Proteínas Represoras/metabolismo , Apoptosis , Western Blotting , Inmunoprecipitación de Cromatina , N-Metiltransferasa de Histona-Lisina/antagonistas & inhibidores , N-Metiltransferasa de Histona-Lisina/genética , Humanos , Inmunoprecipitación , Mieloma Múltiple/genética , Mieloma Múltiple/metabolismo , Proteínas Proto-Oncogénicas c-myc/genética , ARN Mensajero/genética , ARN Interferente Pequeño/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Proteínas Represoras/antagonistas & inhibidores , Proteínas Represoras/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Células Tumorales CultivadasRESUMEN
BCR-ABL-negative myeloproliferative neoplasms (MPNs) are most frequently characterized by the JAK2V617F gain-of-function mutation, but several studies showed that JAK2V617F may not be the initiating event in MPN development, and recent publications indicate that additional alterations such as chromatin modification and microRNA (miRNA) deregulation may have an important role in MPN pathogenesis. Here we report that 61 miRNAs were significantly deregulated in CD34+ cells from MPN patients compared with controls (P<0.01). Global miRNA analysis also revealed that polycythemia vera (JAKV617F) and essential thrombocythemia (JAK2 wild type) patients have significantly different miRNA expression profiles from each other. Among the deregulated miRNAs, expression of miR-134, -214 and -433 was not affected by changes in JAK2 activity, suggesting that additional signaling pathways are responsible for the deregulation of these miRNAs in MPN. Despite its upregulation in MPN CD34+ and during normal erythropoiesis, both overexpression and knockdown studies suggest that miR-433 negatively regulates CD34+ proliferation and differentiation ex vivo. Its novel target GBP2 is downregulated during normal erythropoiesis and regulates proliferation and erythroid differentiation in TF-1 cells, indicating that miR-433 negatively regulates hematopoietic cell proliferation and erythropoiesis by directly targeting GBP2.
Asunto(s)
Biomarcadores de Tumor/genética , Diferenciación Celular , Proliferación Celular , Células Eritroides/citología , MicroARNs/genética , Trastornos Mieloproliferativos/genética , Antígenos CD34/metabolismo , Células Cultivadas , Células Eritroides/metabolismo , Eritropoyesis/fisiología , Proteínas de Unión al GTP/antagonistas & inhibidores , Proteínas de Unión al GTP/genética , Proteínas de Unión al GTP/metabolismo , Perfilación de la Expresión Génica , Humanos , Janus Quinasa 2/genética , Luciferasas/metabolismo , Mutación/genética , Trastornos Mieloproliferativos/metabolismo , Trastornos Mieloproliferativos/patología , Análisis de Secuencia por Matrices de Oligonucleótidos , ARN Mensajero/genética , ARN Interferente Pequeño/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
The WTX, Wilms tumor-associated tumor-suppressor gene, is present on the X chromosome and a single WTX mutation may be sufficient to promote carcinogenesis. Unlike the WT1 tumor suppressor, a transcription factor, WTX lacks conserved functional protein domains. To study the function of WTX, we constructed inducible cell lines expressing WTX and tumor-associated WTX mutants. Induction of WTX inhibited cell growth and caused G(1)/G(0) arrest. In contrast, a short, tumor-associated truncation mutant of WTX358 only slightly inhibited cell growth without a significant cell-cycle arrest, although expression of a longer truncation mutant WTX565 led to the growth inhibition and cell-cycle arrest to a similar extent as wild-type WTX. Like WT1, WTX slowed growth and caused cell-cycle arrest through p21 induction. Gene expression profiling showed that these two tumor-suppressors regulated genes in similar pathways, including those implicated in control of the cellular growth, cell cycle, cell death, cancer and cardiovascular system development. When gene expression changes mediated by wild-type WTX were compared with those affected by mutant forms, WTX565 showed a 55% overlap (228 genes) in differentially regulated genes, whereas WTX358 regulated only two genes affected by wild-type WTX, implying that amino-acid residues 358-561 are critical for WTX function.
Asunto(s)
Regulación Neoplásica de la Expresión Génica , Neoplasias Renales/genética , Proteínas Supresoras de Tumor/genética , Tumor de Wilms/genética , Proteínas Adaptadoras Transductoras de Señales , Línea Celular , Perfilación de la Expresión Génica , Humanos , Riñón/crecimiento & desarrollo , Riñón/metabolismo , Neoplasias Renales/metabolismo , Proteínas Proto-Oncogénicas p21(ras)/metabolismo , Eliminación de Secuencia , Proteínas Supresoras de Tumor/metabolismo , Tumor de Wilms/metabolismoRESUMEN
Polycythemia vera (PV), essential thrombocythemia and primary myelofibrosis, are myeloproliferative neoplasms (MPNs) with distinct clinical features and are associated with the JAK2V617F mutation. To identify genomic anomalies involved in the pathogenesis of these disorders, we profiled 87 MPN patients using Affymetrix 250K single-nucleotide polymorphism (SNP) arrays. Aberrations affecting chr9 were the most frequently observed and included 9pLOH (n=16), trisomy 9 (n=6) and amplifications of 9p13.3-23.3 (n=1), 9q33.1-34.13 (n=1) and 9q34.13 (n=6). Patients with trisomy 9 were associated with elevated JAK2V617F mutant allele burden, suggesting that gain of chr9 represents an alternative mechanism for increasing JAK2V617F dosage. Gene expression profiling of patients with and without chr9 abnormalities (+9, 9pLOH), identified genes potentially involved in disease pathogenesis including JAK2, STAT5B and MAPK14. We also observed recurrent gains of 1p36.31-36.33 (n=6), 17q21.2-q21.31 (n=5) and 17q25.1-25.3 (n=5) and deletions affecting 18p11.31-11.32 (n=8). Combined SNP and gene expression analysis identified aberrations affecting components of a non-canonical PRC2 complex (EZH1, SUZ12 and JARID2) and genes comprising a 'HSC signature' (MLLT3, SMARCA2 and PBX1). We show that NFIB, which is amplified in 7/87 MPN patients and upregulated in PV CD34+ cells, protects cells from apoptosis induced by cytokine withdrawal.
RESUMEN
Immediately following the 2010 annual American Society of Hematology (ASH) meeting, the 5th International Post-ASH Symposium on Chronic Myelogenous Leukemia and BCR-ABL1-Negative Myeloproliferative Neoplasms (MPNs) took place on 7-8 December 2010 in Orlando, Florida, USA. During this meeting, the most recent advances in laboratory research and clinical practice, including those that were presented at the 2010 ASH meeting, were discussed among recognized authorities in the field. The current paper summarizes the proceedings of this meeting in BCR-ABL1-negative MPN. We provide a detailed overview of new mutations with putative epigenetic effects (TET oncogene family member 2 (TET2), additional sex comb-like 1 (ASXL1), isocitrate dehydrogenase (IDH) and enhancer of zeste homolog 2 (EZH2)) and an update on treatment with Janus kinase (JAK) inhibitors, pomalidomide, everolimus, interferon-α, midostaurin and cladribine. In addition, the new 'Dynamic International Prognostic Scoring System (DIPSS)-plus' prognostic model for primary myelofibrosis (PMF) and the clinical relevance of distinguishing essential thrombocythemia from prefibrotic PMF are discussed.
RESUMEN
The activating transcription factor, ATF-2, is a target of p38 and JNK that are involved in stress-induced apoptosis. Heterozygous Atf-2 mutant (Atf-2+/-) mice are highly prone to mammary tumors. The apoptosis-regulated gene GADD45alpha and the breast cancer suppressor gene Maspin, both of which are known to be p53 target genes, are downregulated in the mammary tumors arisen in Atf-2+/- mice. Here, we have analysed how ATF-2 controls the transcription of GADD45alpha and Maspin. ATF-2 and p53 independently activate the GADD45alpha transcription. ATF-2 does not directly bind to the GADD45alpha promoter; instead, it is recruited via Oct-1 and NF-I. ATF-2 simultaneously binds to Oct-1, NF-I and breast cancer suppressor BRCA1 to activate transcription. With regard to Maspin, ATF-2 and p53 directly bind to different sites in the Maspin promoter to independently activate its transcription. Consistent with the observation that ATF-2 and p53 independently activate the transcription of Maspin and GADD45alpha is that the loss of one copy of p53 shortened the period required for mammary tumor development in Atf-2+/- mice. These studies suggest the functional link between the ATF-2 and the two tumor suppressors BRCA1 and p53.
Asunto(s)
Factor de Transcripción Activador 2/fisiología , Proteínas de Ciclo Celular/genética , Regulación Neoplásica de la Expresión Génica/fisiología , Neoplasias Mamarias Experimentales/genética , Neoplasias Mamarias Experimentales/prevención & control , Proteínas Nucleares/genética , Serpinas/genética , Proteína p53 Supresora de Tumor/fisiología , Factor de Transcripción Activador 2/deficiencia , Factor de Transcripción Activador 2/genética , Animales , Proteína BRCA1/fisiología , Proteínas de Ciclo Celular/biosíntesis , Línea Celular , Línea Celular Tumoral , Femenino , Genes Supresores de Tumor/fisiología , Humanos , Masculino , Neoplasias Mamarias Experimentales/enzimología , Neoplasias Mamarias Experimentales/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos CBA , Ratones Noqueados , Ratones Mutantes , Proteínas Nucleares/biosíntesis , Serpinas/biosíntesisRESUMEN
The molecular processes governing hematopoiesis involve the interplay between lineage-specific transcription factors and a series of epigenetic tags, including DNA methylation and covalent histone tail modifications, such as acetylation, methylation, phosphorylation, SUMOylation and ubiquitylation. These post-translational modifications, which collectively constitute the 'histone code', are capable of affecting chromatin structure and gene transcription and are catalysed by opposing families of enzymes, allowing the developmental potential of hematopoietic stem cells to be dynamically regulated. The essential role of these enzymes in regulating normal blood development is highlighted by the finding that members from all families of chromatin regulators are targets for dysregulation in many hematological malignancies, and that patterns of histone modification are globally affected in cancer as well as the regulatory regions of specific oncogenes and tumor suppressors. The discovery that these epigenetic marks can be reversed by compounds targeting aberrant transcription factor/co-activator/co-repressor interactions and histone-modifying activities, provides the basis for an exciting field in which the epigenome of cancer cells may be manipulated with potential therapeutic benefits.
Asunto(s)
Transformación Celular Neoplásica/patología , Epigénesis Genética/fisiología , Neoplasias Hematológicas/etiología , Neoplasias Hematológicas/patología , Hematopoyesis/fisiología , Animales , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Neoplasias Hematológicas/genética , Neoplasias Hematológicas/metabolismo , Hematopoyesis/genética , HumanosRESUMEN
Sprouty (Spry) proteins are ligand-inducible inhibitors of receptor tyrosine kinases-dependent signaling pathways, which control various biological processes, including proliferation, differentiation and survival. Here, we investigated the regulation and the role of Spry2 in cells of the central nervous system (CNS). In primary cultures of immature neurons, the neurotrophic factor BDNF (brain-derived neurotrophic factor) regulates spry2 expression. We identified the transcription factors CREB and SP1 as important regulators of the BDNF activation of the spry2 promoter. In immature neurons, we show that overexpression of wild-type Spry2 blocks neurite formation and neurofilament light chain expression, whereas inhibition of Spry2 by a dominant-negative mutant or small interfering RNA favors sprouting of multiple neurites. In mature neurons that exhibit an extensive neurite network, spry2 expression is sustained by BDNF and is downregulated during neuronal apoptosis. Interestingly, in these differentiated neurons, overexpression of Spry2 induces neuronal cell death, whereas its inhibition favors neuronal survival. Together, our results imply that Spry2 is involved in the development of the CNS by inhibiting both neuronal differentiation and survival through a negative-feedback loop that downregulates neurotrophic factors-driven signaling pathways.
Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/fisiología , Diferenciación Celular/fisiología , Proteínas de la Membrana/metabolismo , Neuronas/citología , Transducción de Señal , Proteínas Adaptadoras Transductoras de Señales , Animales , Apoptosis , Proteína de Unión a CREB/genética , Proteína de Unión a CREB/metabolismo , Proliferación Celular , Supervivencia Celular/fisiología , Células Cultivadas , Retroalimentación Fisiológica , Regulación de la Expresión Génica , Péptidos y Proteínas de Señalización Intracelular , Proteínas de la Membrana/genética , Ratones , Neuronas/metabolismo , Proteínas Serina-Treonina Quinasas , Proteínas Tirosina Quinasas Receptoras/genética , Proteínas Tirosina Quinasas Receptoras/metabolismo , Factor de Transcripción Sp1/genética , Factor de Transcripción Sp1/metabolismoRESUMEN
The PLZF gene is one of five partners fused to the retinoic acid receptor alpha in acute promyelocytic leukemia. PLZF encodes a DNA-binding transcriptional repressor and the PLZF-RARalpha fusion protein like other RARalpha fusions can inhibit the genetic program mediated by the wild tpe retinoic acid receptor. However an increasing body of literature indicates an important role for the PLZF gene in growth control and development. This information suggests that loss of PLZF function might also contribute to leukemogenesis.
Asunto(s)
Cromosomas Humanos Par 11 , Cromosomas Humanos Par 17 , Proteínas de Unión al ADN/genética , Leucemia Promielocítica Aguda/etiología , Leucemia Promielocítica Aguda/genética , Factores de Transcripción/genética , Translocación Genética , Animales , Humanos , Factores de Transcripción de Tipo Kruppel , Proteína de la Leucemia Promielocítica con Dedos de Zinc , Dedos de ZincRESUMEN
PLZF (promyelocytic leukemia zinc finger ) is a transcription factor disrupted in t(11;17)-associated acute promyelocytic leukemia which is highly expressed in undifferentiated myeloid cells. To address the tissue-specific regulation of the promoter, we isolated sequences 1.2-kb 5' to the transcriptional start site. Sequence analysis demonstrated that this region contains one TATA box and several putative transcription factor binding sites including four G/C-rich sites and one Evi-1-like site. A fragment of the promoter spanning 158-bp upstream of the transcription start site displayed relative specificity for PLZF-expressing myeloid cells. Functional promoter assays revealed that an Evi-1-like site at -140/-130 was essential for full promoter activity in every cell line tested while a G-rich site at -15/-7 was important for tissue specificity. Electrophoretic mobility shift assays showed that Evi-1 binds specifically to -140/-130 Evi-1-like site and overexpression of Evi-1 in K562 cells activated the PLZF promoter. UV cross-linking assays showed that the proximal, tissue specific element at -15/-7 bound a novel 28 kDa protein. These results indicate as with other myeloid genes, a relatively small segment of DNA can direct tissue-specific expression, but unlike other myeloid promoters, no critical PU.1 or C/EBP sites were found.
Asunto(s)
Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/fisiología , ADN/metabolismo , Secuencia Rica en GC/fisiología , Leucemia Promielocítica Aguda/genética , Proto-Oncogenes , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Transcripción Genética , Secuencia de Bases , Sitios de Unión , Proteínas de Unión al ADN/metabolismo , Ensayo de Cambio de Movilidad Electroforética , Eliminación de Gen , Regulación Neoplásica de la Expresión Génica , Humanos , Factores de Transcripción de Tipo Kruppel , Leucemia Promielocítica Aguda/metabolismo , Luciferasas/metabolismo , Proteína del Locus del Complejo MDS1 y EV11 , Datos de Secuencia Molecular , Regiones Promotoras Genéticas , Proteína de la Leucemia Promielocítica con Dedos de Zinc , Translocación Genética , Células Tumorales Cultivadas , Dedos de ZincAsunto(s)
Leucemia Promielocítica Aguda/genética , Leucemia Promielocítica Aguda/metabolismo , Transcripción Genética , Adhesión Celular , Inhibidores Enzimáticos/farmacología , Histona Desacetilasas/metabolismo , Humanos , Ácidos Hidroxámicos/metabolismo , Proteínas Recombinantes de Fusión , Tretinoina/metabolismo , VorinostatRESUMEN
Monocyte differentiation induced by 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is interrupted during the course of acute promyelocytic leukemia (APL). One form of APL is associated with the translocation t(11;17), which joins the promyelocytic leukemia zinc finger (PLZF) and retinoic acid receptor alpha (RARalpha) genes. Because PLZF is coexpressed in the myeloid lineage with the vitamin D(3) receptor (VDR), the interplay between PLZF and VDR was examined. It was found that PLZF interacts directly with VDR. This occurred at least partly through contacts in the DNA-binding domain of VDR and the broad complex, tram-trak, bric-a-brac/pox virus zinc finger (BTB/POZ) domain of PLZF. Moreover, PLZF altered the mobility of VDR derived from nuclear extracts when bound to its cognate binding site, forming a slowly migrating DNA-protein complex. Overexpression of PLZF in a monocytic cell line abrogated 1,25(OH)(2)D(3) activation from both a minimal VDR responsive reporter and the promoter of p21(WAF1/CIP1), a target gene of VDR. Deletion of the BTB/POZ domain significantly relieved PLZF-mediated repression of 1,25(OH)(2)D(3)-dependent activation. In addition, stable, inducible expression of PLZF in U937 cells inhibited the ability of 1,25(OH)(2)D(3) to induce surface expression of the monocytic marker CD14 and morphologic changes associated with differentiation. These results suggest that PLZF may play an important role in regulating the process by which 1,25(OH)(2)D(3) induces monocytic differentiation in hematopoietic cells.
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Calcitriol/farmacología , Diferenciación Celular/efectos de los fármacos , Proteínas de Unión al ADN/farmacología , Monocitos/efectos de los fármacos , Receptores de Calcitriol/efectos de los fármacos , Factores de Transcripción/farmacología , Sitios de Unión , Núcleo Celular/química , Inhibidor p21 de las Quinasas Dependientes de la Ciclina , Ciclinas/genética , ADN/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Expresión Génica , Humanos , Factores de Transcripción de Tipo Kruppel , Linfoma de Células B Grandes Difuso , Regiones Promotoras Genéticas , Proteína de la Leucemia Promielocítica con Dedos de Zinc , Receptores de Calcitriol/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Transcripción Genética/efectos de los fármacos , Transfección , Células U937 , Dedos de ZincRESUMEN
Acute promyelocytic leukemia (APL) has been recognized as a distinct clinical entity for over 40 years. Although relatively rare among hematopoietic malignancies (approximately 10% of AML cases), this disease has attracted a particularly good share of attention by becoming the first human cancer in which all-trans-retinoic acid (ATRA), a physiologically active derivative of vitamin A, was able to induce complete remission (CR). ATRA induced remission is not associated with rapid cell death, as in the case of conventional chemotherapy, but with a restoration of the 'normal' granulocytic differentiation pathway. With this remarkable medical success story APL has overnight become a paradigm for the differentiation therapy of cancer. A few years later, excitement with APL was further enhanced by the discovery that a cytogenetic marker for this disease, the t(15:17) reciprocal chromosomal translocation, involves a fusion between the retinoic acid receptor alpha (RARalpha) gene and a previously unknown locus named promyelocytic leukemia (PML). Consequence of this gene rearrangement is expression of the PML-RARalpha chimeric oncoprotein, which is responsible for the cellular transformation as well as ATRA response that is observed in APL. Since this initial discovery, a number of different translocation partner genes of RARalpha have been reported in rarer cases of APL, strongly suggesting that disruption of RARalpha underlies its pathogenesis. This article reviews various rearrangements of the RARalpha gene that have so far been described in literature, functions of the proteins encoded by the different RARalpha partner loci, and implications that these may have for the molecular pathogenesis of APL.
Asunto(s)
Leucemia Promielocítica Aguda/genética , Proteínas de la Leche , Receptores de Ácido Retinoico/genética , Translocación Genética/genética , Antígenos Nucleares , Proteínas de Ciclo Celular , Proteínas de Unión al ADN/genética , Humanos , Leucemia Promielocítica Aguda/tratamiento farmacológico , Proteínas de Neoplasias/genética , Proteínas Asociadas a Matriz Nuclear , Proteínas Nucleares/genética , Nucleofosmina , Proteínas de Fusión Oncogénica/genética , Receptor alfa de Ácido Retinoico , Factor de Transcripción STAT5 , Transactivadores/genética , TretinoinaRESUMEN
Sprouty was genetically identified as an antagonist of fibroblast growth factor signaling during tracheal branching in Drosophila. In this study, we provide a functional characterization of mammalian Sprouty1 and Sprouty2. Sprouty1 and Sprouty2 inhibited events downstream of multiple receptor tyrosine kinases and regulated both cell proliferation and differentiation. Using NIH3T3 cell lines conditionally expressing Sprouty1 or Sprouty2, we found that these proteins specifically inhibit the Ras/Raf/MAP kinase pathway by preventing Ras activation. In contrast, activation of the phosphatidylinositol 3-kinase pathway was not affected by Sprouty1 or Sprouty2. We further showed that Sprouty1 and Sprouty2 do no prevent the formation of a SNT.Grb2.Sos complex upon fibroblast growth factor stimulation, yet block Ras activation. Taken together, these results establish mammalian Sprouty proteins as important negative regulators of growth factor signaling and suggest that Sprouty proteins act downstream of the Grb2.Sos complex to selectively uncouple growth factor signals from Ras activation and the MAP Kinase pathway.
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Diferenciación Celular/fisiología , División Celular/fisiología , Proteínas de la Membrana/fisiología , Proteínas del Tejido Nervioso/fisiología , Fosfoproteínas/fisiología , Proteínas ras/antagonistas & inhibidores , Células 3T3 , Proteínas Adaptadoras Transductoras de Señales , Animales , Western Blotting , Sistema de Señalización de MAP Quinasas , Ratones , Células PC12 , Pruebas de Precipitina , Ratas , Proteínas ras/metabolismoAsunto(s)
Cromosomas Humanos Par 21 , Cromosomas Humanos Par 8 , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/fisiología , Leucemia Mieloide Aguda/etiología , Leucemia Mieloide Aguda/genética , Proteínas de Fusión Oncogénica/genética , Proteínas de Fusión Oncogénica/metabolismo , Proteínas de Fusión Oncogénica/fisiología , Proteínas Proto-Oncogénicas , Factores de Transcripción/genética , Factores de Transcripción/fisiología , Translocación Genética , Animales , Subunidad alfa 2 del Factor de Unión al Sitio Principal , Humanos , Modelos Genéticos , Familia de Multigenes , Proteína 1 Compañera de Translocación de RUNX1 , Relación Estructura-Actividad , Transcripción GenéticaRESUMEN
AP-2 transcription factors are sequence-specific DNA-binding proteins expressed in neural crest and other tissues during mammalian development. Three mammalian genes, AP-2alpha, AP-2beta, and AP-2gamma, have been reported previously. A partial predicted AP-2 gene was identified in tandem with AP-2beta on human chromosome 6p12-p21.1. The orthologous mouse gene, which we named Ap-2delta, was identified from a fetal mouse head cDNA library. Northern analysis revealed two transcripts in embryonic and newborn mouse brain, with markedly higher steady-state levels in the former. The predicted Ap-2delta protein comprised 452 amino acids and was highly similar to other AP-2 proteins across the DNA-binding and dimerization domains. Ap-2delta formed homodimers and heterodimers in vitro, bound an optimized AP-2 consensus DNA sequence, and transactivated gene expression in eukaryotic cells. Ap-2delta dimers bound poorly to an AP-2 binding sequence from the human metallothionein IIa promoter in vitro, revealing a sequence specificity not previously observed among other AP-2 proteins. The PY motif and critical residues in the transactivation domain, which are highly conserved in the AP-2 family and believed necessary for transactivation, were divergent in Ap-2delta. The unique protein sequence and functional features of Ap-2delta suggest mechanisms, besides tissue-specific AP-2 gene expression, for specific control of target gene activation.