RESUMO
PURPOSES: To inform about a case of Revesz syndrome (RS) with initial ophthalmological symptomatology of severe proliferative vitreoretinopathy of the left eye (LE). After the aplastic anemia had developed, RS was established. The exudative retinopathy was successfully treated with photocoagulation on the right eye (RE). BACKGROUND: RS is characterized by fatal bone marrow failure, exudative retinopathy, neuroradiographic abnormalities, neurodevelopmental delay and skin abnormalities. Non-treated exudative retinopathy leads to blindness. METHODS: We report ophthalmological findings as follows: fundus photography and fluorescein angiography (FA) acquired by examinations under general anesthesia in patient with RS. Results of genetic tests helped to establish the diagnosis. RESULTS: Twoyear old Caucasian male was examined due to total retinal detachment on LE and signs of chorioretinal scarring on RE. In preoperative screening, thrombocytopenia was detected; later, severe pancytopenia developed. Considering the hematological findings and clinical appearance, we suspected RS, which was confirmed by genetic tests. We found a pathogenic mutation in gene TINF2 (variant c.865C>T;p.Pro289Ser) in a mosaic state with autosomal dominant mode of inheritance. This mutation has not been described in RS yet. Blind LE was enucleated because of dolorous neovascular glaucoma. FA of RE shows excessive areas of capillary nonperfusion with vascular abnormalities and exudation. After the photocoagulation, the visual acuity (VA) on RE remains 0.9 at the age of 7 years. CONCLUSIONS: RS is an extremely rare condition. The initial symptomatology could be ophthalmological or hematological. The positive finding of TINF2 gene mutation helped in establishing the correct diagnosis. The ischemic retinopathy was successfully treated by photocoagulation (Fig. 6, Ref. 6). Text in PDF www.elis.sk.
Assuntos
Anemia Aplástica , Doenças Ósseas Metabólicas , Doenças Retinianas , Anemia Aplástica/complicações , Doenças Ósseas Metabólicas/complicações , Pré-Escolar , Humanos , Fotocoagulação a Laser , Masculino , Retina/patologia , Doenças Retinianas/diagnóstico , Doenças Retinianas/etiologia , Acuidade VisualRESUMO
Congenital disorders of glycosylation (CDG) are a group of hereditary metabolic diseases characterized by abnormal glycosylation of proteins and lipids. Often, multisystem disorders with central nervous system involvement and a large variety of clinical symptoms occur. The main characteristics are developmental delay, seizures, and ataxia. In this paper we report the clinical and biochemical characteristics of a 5-year-old girl with a defective galactosylation of N-glycans, resulting in developmental delay, muscular hypotonia, epileptic seizures, inverted nipples, and visual impairment. Next generation sequencing revealed a de novo mutation (c.797G > T, p.G266V) in the X-chromosomal gene SLC35A2 (solute carrier family 35, UDP-galactose transporter, member A2; MIM 300896). While this mutation was found heterozygous, random X-inactivation of the normal allele will lead to loss of normal SLC35A2 activity in respective cells. The functional relevance of the mutation was demonstrated by complementation of UGT-deficient MDCK-RCA(r) and CHO-Lec8 cells by normal UGT-expression construct but not by the mutant version. The effect of dietary galactose supplementation on glycosylation was investigated, showing a nearly complete normalization of transferrin glycosylation.
Assuntos
Defeitos Congênitos da Glicosilação/genética , Defeitos Congênitos da Glicosilação/terapia , Proteínas de Transporte de Monossacarídeos/genética , Animais , Células CHO , Pré-Escolar , Cricetinae , Cricetulus , Análise Mutacional de DNA , Cães , Feminino , Galactose/uso terapêutico , Humanos , Células Madin Darby de Rim Canino , Proteínas de Transporte de Monossacarídeos/deficiência , FenótipoRESUMO
OBJECTIVE: To assess the types and numbers of cases, gestational age at specific prenatal diagnosis and diagnostic accuracy of the diagnosis of skeletal dysplasias in a prenatal population from a single tertiary center. METHODS: This was a retrospective database review of type, prenatal and definitive postnatal diagnoses and gestational age at specific prenatal diagnosis of all cases of skeletal dysplasias from a mixed referral and screening population between 1985 and 2007. Prenatal diagnoses were grouped into 'correct ultrasound diagnosis' (complete concordance with postnatal pediatric or pathological findings) or 'partially correct ultrasound diagnosis' (skeletal dysplasias found postnatally to be a different one from that diagnosed prenatally). RESULTS: We included 178 fetuses in this study, of which 176 had a prenatal ultrasound diagnosis of 'skeletal dysplasia'. In 160 cases the prenatal diagnosis of a skeletal dysplasia was confirmed; two cases with skeletal dysplasias identified postnatally had not been diagnosed prenatally, giving 162 fetuses with skeletal dysplasias in total. There were 23 different classifiable types of skeletal dysplasia. The specific diagnoses based on prenatal ultrasound examination alone were correct in 110/162 (67.9%) cases and partially correct in 50/162 (30.9%) cases, (160/162 overall, 98.8%). In 16 cases, skeletal dysplasia was diagnosed prenatally, but was not confirmed postnatally (n = 12 false positives) or the case was lost to follow-up (n = 4). The following skeletal dysplasias were recorded: thanatophoric dysplasia (35 diagnosed correctly prenatally of 40 overall), osteogenesis imperfecta (lethal and non-lethal, 31/35), short-rib dysplasias (5/10), chondroectodermal dysplasia Ellis-van Creveld (4/9), achondroplasia (7/9), achondrogenesis (7/8), campomelic dysplasia (6/8), asphyxiating thoracic dysplasia Jeune (3/7), hypochondrogenesis (1/6), diastrophic dysplasia (2/5), chondrodysplasia punctata (2/2), hypophosphatasia (0/2) as well as a further 7/21 cases with rare or unclassifiable skeletal dysplasias. CONCLUSION: Prenatal diagnosis of skeletal dysplasias can present a considerable diagnostic challenge. However, a meticulous sonographic examination yields high overall detection. In the two most common disorders, thanatophoric dysplasia and osteogenesis imperfecta (25% and 22% of all cases, respectively), typical sonomorphology accounts for the high rates of completely correct prenatal diagnosis (88% and 89%, respectively) at the first diagnostic examination.
Assuntos
Doenças do Desenvolvimento Ósseo/diagnóstico por imagem , Anormalidades Musculoesqueléticas/diagnóstico por imagem , Algoritmos , Biometria , Doenças do Desenvolvimento Ósseo/embriologia , Doenças do Desenvolvimento Ósseo/genética , Feminino , Aconselhamento Genético , Idade Gestacional , Humanos , Anormalidades Musculoesqueléticas/embriologia , Anormalidades Musculoesqueléticas/genética , Gravidez , Resultado da Gravidez , Diagnóstico Pré-Natal , Garantia da Qualidade dos Cuidados de Saúde , Estudos Retrospectivos , UltrassonografiaRESUMO
Pantothenate kinase-associated neurodegeneration (PKAN), formerly Hallervorden-Spatz syndrome, is a rare autosomal recessive disorder characterized by extrapyramidal dysfunction as demonstrated by dystonia, rigidity, and choreoathetosis. Iron deposition in conjunction with destruction of the globus pallidus gives rise to the characteristic eye-of-the-tiger sign in MRI. It has been postulated that pantothenate kinase 2 mutations underlying all cases of classic Hallervorden-Spatz syndrome are always associated with the eye-of-the-tiger sign. Here, we report a patient with classic Hallervorden-Spatz syndrome and a homozygous pantothenate kinase 2 mutation in whom the initially present eye-of-the-tiger sign vanished during the course of the disease. Thus, the alleged one-to-one correlation between the eye-of-the-tiger sign and the presence of pantothenate kinase 2 mutation does not hold true over the course of the disease in PKAN.
Assuntos
Encéfalo/patologia , Neurodegeneração Associada a Pantotenato-Quinase/patologia , Criança , Feminino , Seguimentos , Humanos , Imageamento por Ressonância Magnética , Reprodutibilidade dos TestesRESUMO
Common clinical, radiologic, and pathologic features in infantile neuroaxonal dystrophy (INAD) and pantothenate kinase-associated neurodegeneration (PKAN) have led to the hypothesis of an allelic relationship. With the discovery of the gene defect in PKAN, this can now be tested directly. The authors excluded linkage in one consanguineous INAD family by haplotype analysis. Moreover, sequencing in seven INAD families revealed no mutations in PANK2 or in other genes of CoA biogenesis. Thus, INAD and PKAN are genetically heterogeneous disorders.
Assuntos
Heterogeneidade Genética , Distrofias Neuroaxonais/genética , Neurodegeneração Associada a Pantotenato-Quinase/genética , Fosfotransferases (Aceptor do Grupo Álcool)/genética , Alelos , Axônios/patologia , Coenzima A/biossíntese , Feminino , Marcadores Genéticos , Genótipo , Haplótipos/genética , Humanos , Masculino , Repetições de Microssatélites , LinhagemRESUMO
The aim of the MitoP2 database (http://ihg.gsf.de/mitop2) is to provide a comprehensive list of mitochondrial proteins of yeast and man. Based on the current literature we created an annotated reference set of yeast and human proteins. In addition, data sets relevant to the study of the mitochondrial proteome are integrated and accessible via search tools and links. They include computational predictions of signalling sequences, and summarize results from proteome mapping, mutant screening, expression profiling, protein-protein interaction and cellular sublocalization studies. For each individual approach, specificity and sensitivity for allocating mitochondrial proteins was calculated. By providing the evidence for mitochondrial candidate proteins the MitoP2 database lends itself to the genetic characterization of human mitochondriopathies.
Assuntos
Bases de Dados Genéticas , Proteínas Mitocondriais , Proteoma , Proteínas de Saccharomyces cerevisiae , Biologia Computacional , Humanos , Armazenamento e Recuperação da Informação , Internet , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Mutação , Ligação Proteica , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMO
Deregulated expression of the proto-oncogene c- myc in Burkitt lymphoma (BL) cells carrying a t(2;8) translocation is mediated by a synergistic interaction of the translocated immunoglobulin (Ig) kappa gene intron (kappaEi) and 3' (kappaE3') enhancers and characterized by a strong activation of the promoter P1. We have investigated the functional role of distinct kappa enhancer sequence motifs in P1 activation on both mini-chromosomes and reporter gene constructs. Stable and transient transfections of BL cells revealed critical roles of the kappaEi and kappaE3' elements kappaB and PU, respectively. Joint mutation of kappaB and PU completely abolished P1 activity, implying that an interaction of kappaB- and PU-binding factors is essential for the enhancer synergism. Mutation of the E box 1 and E box 2 motifs markedly decreased P1 activity in transient but not in stable transfection experiments. Co-expression of the NF-kappaB subunit p65(RelA) and Sp1, an essential factor for P1 transcription, in Drosophila melanogaster SL2 cells synergistically enhanced promoter activity. Our results support a model which proposes cross-talk between promoter and enhancer binding factors as the basic mechanism for kappa enhancer-mediated c- myc activation in BL cells.
Assuntos
Linfoma de Burkitt/genética , Elementos Facilitadores Genéticos/genética , Genes myc/genética , Cadeias kappa de Imunoglobulina/genética , Elementos de Resposta/genética , Ativação Transcricional/genética , Animais , Sequência de Bases , Linfoma de Burkitt/patologia , Linhagem Celular , Cromossomos/genética , Drosophila melanogaster/citologia , Regulação Neoplásica da Expressão Gênica/genética , Genes Reporter/genética , Íntrons/genética , Mutação/genética , NF-kappa B/genética , NF-kappa B/metabolismo , Regiões Promotoras Genéticas/genética , Fator de Transcrição Sp1/genética , Fator de Transcrição Sp1/metabolismo , Fator de Transcrição RelA , Transfecção , Translocação Genética/genéticaRESUMO
In Burkitt's lymphoma (BL) cells the proto-oncogene c-myc is juxtaposed to one of the immunoglobulin (Ig) loci on chromosomes 2, 14, or 22. The c-myc gene becomes transcriptionally activated as a consequence of the chromosomal translocation and shows preferential usage of promoter P1 over P2, a phenomenon referred to as promoter shift. In order to define the responsible regulatory elements within the Ig lambda locus, we studied the effect of the human Ig lambda enhancer (HuE lambda) on c-myc expression after stable transfection into BL cells. A 12 kb genomic fragment encompassing HuE lambda, but not HuE lambda alone, strongly activated c-myc expression and induced the promoter shift. To identify additional elements involved in c-myc deregulation, we mapped DNaseI hypersensitive sites within the 12 kb lambda fragment on the construct. Besides one hypersensitive site corresponding to HuE lambda, three additional sites were detected. Two of these elements displayed enhancer activity after transient transfection. The third element did not activate c-myc transcription, but was required for full c-myc activation and promoter shift. Deletion analyses of the c-myc promoter identified the immediate promoter region as sufficient for activation by the Ig lambda. locus, but also revealed that induction of the promoter shift requires additional upstream elements.
Assuntos
Linfoma de Burkitt/genética , Cromossomos Humanos Par 22 , Cromossomos Humanos Par 8 , Regulação Neoplásica da Expressão Gênica , Proteínas Proto-Oncogênicas c-myc/genética , Translocação Genética , Sítios de Ligação , Butiratos/farmacologia , Desoxirribonuclease I , Regulação para Baixo , Elementos Facilitadores Genéticos , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Cadeias lambda de Imunoglobulina/genética , Regiões Promotoras Genéticas , Proto-Oncogene Mas , TransfecçãoRESUMO
The disordered mobile loop L2 of the Escherichia coli RecA protein is known to play a central role in DNA binding and pairing. To investigate the local chemical environment in relation to function we performed saturation mutagenesis of the loop L2 region (amino acid positions 193-212) using a site-directed mutagenesis procedure, and determined the recombinational proficiency of the 380 mutants using genetic assays for homologous recombination and recombinational repair. Residues Asn193, Gln194, Arg196, Glu207, Thr209, Gly211, and Gly212 were identified as stringently required for recombinational events in bacterial cells. In addition, our findings suggest the involvement of loop L2 in the ATPase activity of RecA, and a role for residues Gln194, Arg196, Lys198 and Thr209 in the DNA-dependent hydrolysis of ATP. Finally, since 20 residue peptides that comprise this region can pair homologous DNAs by forming filamentous beta-structures, we propose how the information from the mutant analysis might facilitate the use of a simplified amino acid alphabet to design beta-structure forming L2 peptides with improved RecA-like activities.
Assuntos
Reparo do DNA , Escherichia coli/genética , Recombinases Rec A/metabolismo , Recombinação Genética , Modelos Moleculares , Mutagênese Sítio-Dirigida , Conformação de Ácido Nucleico , Conformação Proteica , Recombinases Rec A/química , Recombinases Rec A/genéticaRESUMO
Wolfram syndrome is an autosomal recessive disorder characterized by juvenile diabetes mellitus, diabetes insipidus, optic atrophy and a number of neurological symptoms including deafness, ataxia and peripheral neuropathy. Mitochondrial DNA deletions have been described in a few patients and a locus has been mapped to 4p16 by linkage analysis. Susceptibility to psychiatric illness is reported to be high in affected individuals and increased in heterozygous carriers in Wolfram syndrome families. We screened four candidate genes in a refined critical linkage interval covered by an unfinished genomic sequence of 600 kb. One of these genes, subsequently named wolframin, codes for a predicted transmembrane protein which was expressed in various tissues, including brain and pancreas, and carried loss-of-function mutations in both alleles in Wolfram syndrome patients.
Assuntos
Genes/genética , Proteínas de Membrana/genética , Síndrome de Wolfram/genética , Adolescente , Adulto , Sequência de Aminoácidos , Animais , Criança , Cromossomos Humanos Par 4/genética , DNA/química , DNA/genética , DNA/isolamento & purificação , Éxons , Saúde da Família , Feminino , Marcadores Genéticos , Humanos , Íntrons , Masculino , Camundongos , Dados de Sequência Molecular , Mutação , Linhagem , Mapeamento Físico do Cromossomo , Polimorfismo Conformacional de Fita Simples , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência de AminoácidosRESUMO
Organization of DNA into chromatin has been shown to contribute to a repressed state of gene transcription. Disruption of nucleosomal structure is observed in response to gene induction, suggesting a model in which RNA polymerase II (pol II) is recruited to the promoter upon reorganization of nucleosomes. Here we show that induction of c-myc transcription correlates with the disruption of two nucleosomes in the upstream promoter region. This nucleosomal disruption, however, is not necessary for the binding of pol II to the promoter. Transcriptionally engaged pol II complexes can be detected when the upstream chromatin is in a more closed configuration. Thus, upstream chromatin opening is suggested to affect activation of promoter-bound pol II rather than entry of polymerases into the promoter. Interestingly, pol II complexes are detectable in both sense and antisense transcriptional directions, but only complexes in the sense direction respond to activation signals resulting in processive transcription.
Assuntos
Genes myc/genética , Nucleossomos , Regiões Promotoras Genéticas , RNA Polimerase II/metabolismo , Transcrição Gênica , Linfócitos B , Linhagem Celular Transformada , Cromatina/química , Pegada de DNA , Células HL-60 , Humanos , Nucleossomos/enzimologia , RNA Polimerase II/análise , Ativação Transcricional , TransfecçãoRESUMO
The Schimmelpenning-Feuerstein-Mims syndrome (SFM), characterized by linear nevus sebaceous and ocular and neurologic abnormalities, is a sporadic condition without known familial cases or etiology. We report the occurrence of SFM in only one of two monozygotic (MZ) twins. After considering a variety of possible causative mechanisms, we suggest that a postzygotic dominant lethal mutation in mosaic form may best explain SFM and the discordancy for SFM in these MZ twins.
Assuntos
Anormalidades Múltiplas/genética , Gêmeos Monozigóticos , Anormalidades Múltiplas/patologia , Anormalidades Múltiplas/fisiopatologia , Pré-Escolar , Anormalidades do Olho/genética , Anormalidades do Olho/patologia , Anormalidades do Olho/fisiopatologia , Humanos , SíndromeRESUMO
Two genetic events contribute to the development of endemic Burkitt lymphoma (BL) infection of B lymphocytes with Epstein-Barr virus (EBV) and the activation of the protooncogene c-myc through chromosomal translocation. The viral genes EBV nuclear antigen 2 (EBNA2) and latent membrane protein 1 (LMP1) are essential for transformation of primary human B cells by EBV in vitro; however, these genes are not expressed in BL cells in vivo. To address the question whether c-myc activation might abrogate the requirement of the EBNA2 and LMP1 function, we have introduced an activated c-myc gene into an EBV-transformed cell line in which EBNA2 was rendered estrogen-dependent through fusion with the hormone binding domain of the estrogen receptor. The c-myc gene was placed under the control of regulatory elements of the immunoglobulin kappa locus composed a matrix attachment region, the intron enhancer, and the 3' enhancer. We show here that transfection of a c-myc expression plasmid followed by selection for high MYC expression is capable of inducing continuous proliferation of these cells in the absence of functional EBNA2 and LMP1. c-myc-induced hormone-independent proliferation was associated with a dramatic change in the growth behavior as well as cell surface marker expression of these cells. The typical lymphoblastoid morphology and phenotype of EBV-transformed cells completely changed into that of BL cells in vivo. We conclude that the phenotype of BL cells reflects the expression pattern of viral and cellular genes rather than its germinal center origin.
Assuntos
Antígenos Nucleares do Vírus Epstein-Barr/biossíntese , Regulação Viral da Expressão Gênica , Genes myc , Herpesvirus Humano 4/fisiologia , Transativadores/biossíntese , Proteínas da Matriz Viral/biossíntese , Antígenos CD/biossíntese , Linfoma de Burkitt , Divisão Celular , Linhagem Celular Transformada , Estrogênios/farmacologia , Citometria de Fluxo , Herpesvirus Humano 4/genética , Humanos , Proteínas Proto-Oncogênicas c-myc/biossíntese , Receptores de Estrogênio/biossíntese , Proteínas Recombinantes de Fusão/biossíntese , TransfecçãoRESUMO
50 kb of contiguous DNA sequences covering the human c-myc coding region and approximately 20 kb of flanking upstream and downstream sequences were cloned onto a prokaryotic F-factor derived plasmid, which also contains a selectable marker and the plasmid origin of DNA replication oriP of Epstein Barr virus (EBV). Since these plasmids replicate extrachromosomally after stable transfection into EBV-positive B-cell lines, the gene regulation of c-myc can be analysed independent from chromosomal integration positions. Despite the presence of all known c-myc regulatory elements on these constructs, expression from the stably transfected c-myc gene was barely detectable in either cell line. Hypermethylation of these plasmids could be excluded as a mechanism for the lack of gene expression. Insertion of the immunoglobulin kappa-intron and 3' enhancers, however, activated c-myc transcription, when placed adjacent to or separated from the c-myc promoters by as far as 30 kb. These results indicate that transcription of c-myc in vivo requires additional and still unidentified control elements located outside this 50 kb fragment, and experimentally demonstrate long range enhancer function in vivo.
Assuntos
Linfoma de Burkitt/genética , Elementos Facilitadores Genéticos , Regulação Neoplásica da Expressão Gênica , Genes myc , Cadeias kappa de Imunoglobulina/genética , Íntrons , Sequência de Bases , Linhagem Celular Transformada , Cromatina/fisiologia , Cromossomos Humanos , DNA de Neoplasias/genética , Fosfatos de Dinucleosídeos/metabolismo , Herpesvirus Humano 4 , Humanos , Cadeias kappa de Imunoglobulina/fisiologia , Metilação , Dados de Sequência Molecular , Plasmídeos/genética , Regiões Promotoras Genéticas , TransfecçãoRESUMO
In Burkitt's lymphoma (BL) cells the proto-oncogene c-myc is transcriptionally activated by chromosomal translocation to the immunoglobulin (Ig) gene loci. This activation is characterized by preferential transcription from the c-myc promoter P1 and accomplished by juxtaposed Ig enhancer elements. To identify promoter elements required for enhancer-activated P1 transcription, we studied the activation of c-myc reporter gene constructs by the Ig kappa intron and 3' enhancers. Deletion analysis defined the core promoter with a TATA box and two adjacent GC/GT boxes upstream sufficient for basal and enhancer-activated transcription. Gel retardation assays revealed Sp1's binding affinity to the GC/GT box proximal to the TATA box to be higher than to the distal one. This difference correlated well with the resulting levels of transcription mediated by Sp1 in contransfection experiments in BL and Sp1-deficient SL2 cells. Sp3 also bound to the core promoter in vitro, but failed to transactivate in vivo. Mutation of the distal Sp1 site moderately affected basal transcription concomitant with a modest decrease in enhancer stimulation. Mutation of the proximal Sp1 site almost entirely abolished basal as well as enhanced transcription. A considerable level of basal transcription was maintained upon mutation of the TATA box, whereas enhancer-activated transcription largely was abolished. Stable transfection of the BL cell line Raji with constructs containing core promoter mutations confirmed that the proximal Sp1 site and the TATA box are essential for the activation of promoter P1 by the Ig kappa enhancers.
Assuntos
Elementos Facilitadores Genéticos , Genes myc , Cadeias kappa de Imunoglobulina/genética , Regiões Promotoras Genéticas , Fator de Transcrição Sp1/metabolismo , TATA Box , Linfoma de Burkitt/genética , Linfoma de Burkitt/patologia , Células Cultivadas , Humanos , Ligação Proteica , Proto-Oncogene Mas , Transcrição Gênica , Células Tumorais CultivadasRESUMO
Burkitt's lymphoma cells are characterized by chromosomal translocations involving the proto-oncogene c-myc on chromosome 8 and one of the immunoglobulin gene loci on chromosome 2, 14 or 22. The translocated c-myc allele is transcriptionally activated, shows a preferential usage of promoter P1 over P2 (promoter shift) and lacks the ability to retain the transcription complex at the P2 promoter. In order to define the elements of the immunoglobulin kappa gene involved in deregulation of c-myc in a t(2;8) translocation, we designed constructs consisting of c-myc and different parts of the immunoglobulin kappa gene locus. Chromatin analysis of these stably transfected constructs revealed DNase I hypersensitive sites within the c-myc 5' region characteristic for an actively transcribed c-myc gene and three sites within the immunoglobulin kappa locus corresponding to the matrix attachment region, the intron and 3' enhancers, respectively. These three regulatory elements were necessary and sufficient for maximal c-myc activation and formation of the promoter shift. Kinetic nuclear run on experiments were performed to study the distribution of transcription complexes on c-myc exon 1 on constructs with and without the immunoglobulin kappa regulatory elements. The absence of a pausing polymerase complex at the c-myc P2 promoter could be demonstrated for constructs consisting of c-myc and the two kappa enhancers. Therefore the two enhancers are sufficient to relief the elongational block at the P2 promoter, however, the matrix attachment region is additionally required for maximal c-myc activation observed in Burkitt's lymphoma cells.
Assuntos
Linfoma de Burkitt/genética , Elementos Facilitadores Genéticos , Regulação Neoplásica da Expressão Gênica , Genes myc , Cadeias kappa de Imunoglobulina/genética , Regiões Promotoras Genéticas , Sequência de Bases , Cromossomos Humanos Par 2 , Cromossomos Humanos Par 8 , Desoxirribonuclease I , Humanos , Dados de Sequência Molecular , Sondas de Oligonucleotídeos/química , Proto-Oncogene Mas , RNA Mensageiro/genética , Sequências Reguladoras de Ácido Nucleico , Transcrição Gênica , Translocação GenéticaAssuntos
Linfoma de Burkitt/genética , Cromossomos Humanos Par 8/ultraestrutura , Regulação Neoplásica da Expressão Gênica , Genes de Imunoglobulinas , Genes myc , Cadeias kappa de Imunoglobulina/genética , Sequências Reguladoras de Ácido Nucleico , Translocação Genética , Linfoma de Burkitt/patologia , Cromossomos Humanos Par 14/ultraestrutura , Cromossomos Humanos Par 2/ultraestrutura , Elementos Facilitadores Genéticos , Vetores Genéticos , Humanos , Plasmídeos , Regiões Promotoras Genéticas , TransfecçãoRESUMO
In Burkitt's lymphoma cells the proto-oncogene c-myc is constantly juxtaposed through chromosomal translocation to one of the immunoglobulin loci on chromosomes 14, 2 or 22. In the majority of cases the chromosomal breakpoint is localized 3' or 5' of the gene leaving the physiological c-myc transcription unit intact. As a consequence of the translocation the c-myc gene on the translocation chromosome becomes transcriptionally activated in such a manner that the c-myc promoter P1 is more active than promoter P2. In order to define elements involved in c-myc activation through t(2;8) translocation we have studied the expression of constructs consisting of c-myc and different parts of the immunoglobulin kappa locus after stable transfection into Burkitt's lymphoma cells. The c-myc gene under the control of the complete Ig kappa locus containing matrix attachment region, intron enhancer, constant kappa gene and 3' enhancer was strongly activated with predominant usage of promoter P1. Deletion analysis revealed that the intron or 3' enhancers alone activated c-myc to a much lesser extent and with normal promoter usage (P1 < P2). The cooperation of the same regulatory elements is required not only for transcriptional activation and induction of the promoter shift but also for down-regulation of promoter P1 of the translocated c-myc allele by sodium butyrate, another characteristic feature of Burkitt's lymphoma cells. This supports the notion that all elements involved in transcriptional activation and dysregulation of c-myc are contained within the myc-Ig specific minichromosome.