RESUMO
We previously identified the TFPT (FB1) gene as a molecular partner of TCF3 (E2A) in childhood pre-B cell acute lymphoblastic leukemia (ALL). TFPT (FB1) alignment in man, mouse and rat displays a very high degree of identity, indicating that it may play a basic role in mammalian cells. To get insights into this role, we have identified and studied the TFPT (FB1) promoter and its responsiveness to hematopoietic transcriptional factors. We found that the TFPT (FB1) 5' flanking sequence displays the features of a TATA-less promoter with weak homology to Inr (Initiator) elements. Starvation experiments suggested that TFPT (FB1) expression might be constitutive. Nevertheless, the TFPT (FB1) promoter, tested by transactivation assays, was found to be responsive to Ikaros 2 and, mainly, to PU.1, a transcription factor belonging to the Ets family. Thus, these hematopoietic factors, known to play critical roles during the early stages of B cell differentiation and to be involved in leukemia, might modulate TFPT (FB1) expression during hematopoiesis and/or leukemia development.
Assuntos
Proteínas de Ligação a DNA/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Regiões Promotoras Genéticas , Sequência de Aminoácidos , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Linhagem Celular , Criança , Sequência Conservada , Proteínas de Ligação a DNA/biossíntese , Éxons , Genes Reporter , Humanos , Íntrons , Camundongos , Dados de Sequência Molecular , Proteínas de Fusão Oncogênica/fisiologia , Leucemia-Linfoma Linfoblástico de Células Precursoras/metabolismo , RNA Mensageiro/biossíntese , Ratos , Homologia de Sequência de Aminoácidos , Transativadores/fisiologia , Fatores de Transcrição/genética , Ativação Transcricional , TransfecçãoRESUMO
The 'promiscuous' E2A gene, at 19p13.3, is fused with two different molecular partners, PBX1 and HLF, following two chromosome translocations recurrent in childhood pre-B ALL. We have identified a novel gene, FB1, by virtue of its fusion with E2A and by a combination of molecular techniques. FB1 was localized on 19q13.4, suggesting that the novel chimera originated by a cryptic rearrangement of chromosome 19. Two FB1 transcripts, of 1.2 kb and 1.1 kb, are differentially expressed at low level in a variety of human tissues, including hemopoietic cell lines from different lineages. Accordingly, FB1 cDNA displays high homology with a number of cDNA clones from different human tissues. High homology was found also with cDNA clones from mouse and rat, suggesting that the sequence might be conserved at least among mammals. The function of the putative FB1 protein, however, is currently unknown as database sequence comparisons have failed to reveal strong homology with known proteins. The E2A/FB1 fusion appears to be a recurrent feature of pre-B ALLs, suggesting that it might have a role in the development and/or progression of leukemogenesis.
Assuntos
Proteínas E2 de Adenovirus/genética , Proteínas de Ligação a DNA/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras B/genética , Fatores de Transcrição , Sequência de Aminoácidos , Sequência de Bases , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Criança , Mapeamento Cromossômico , Cromossomos Artificiais de Levedura , Cromossomos Humanos Par 19 , Clonagem Molecular , DNA Complementar , Humanos , Dados de Sequência Molecular , RNA Mensageiro/genéticaRESUMO
Several partner genes on different chromosomes have been reported to be fused with the ETV6 gene (located in chromosome band 12p13), with different breakpoints and different frequencies, in various hematologic malignancies, particularly acute myeloid and lymphoid leukemias and myelodysplastic syndromes. By using FISH and molecular analyses, we have analyzed five different pediatric and adult patients carrying cytogenetic abnormalities involving 12p13. Our findings demonstrate that ETV6 was rearranged in all the cases analyzed. In particular, ETV6 was disrupted by translocations with chromosomal bands 7q22, 7q36, 9q11, and 13q12, not previously described as partners of ETV6 in translocations, thus extending its promiscuity in rearranging with different partner genes.
Assuntos
Cromossomos Humanos/genética , Proteínas de Ligação a DNA/genética , Leucemia Mieloide/genética , Proteínas Repressoras , Fatores de Transcrição/genética , Translocação Genética , Adulto , Cromossomos Humanos Par 12/genética , Cromossomos Humanos Par 13/genética , Cromossomos Humanos Par 7/genética , Cromossomos Humanos Par 9/genética , Feminino , Deleção de Genes , Humanos , Lactente , Cariotipagem , Leucemia Mieloide Aguda/genética , Masculino , Pessoa de Meia-Idade , Síndromes Mielodisplásicas/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Proteínas Proto-Oncogênicas c-ets , Variante 6 da Proteína do Fator de Translocação ETSRESUMO
Juvenile myelomonocytic leukemia (JMML) is a rare disorder of early childhood, to which no recurrent chromosome rearrangement has been yet associated. We report a case where leukemic cells harbored a 46,XX,der(12)t(3;12) (q21 approximately 22;p13.33) karyotype, resulting in partial trisomy of 3q. The origin of chromosome material translocated to chromosome 12 was assessed by chromosome painting using a whole chromosome 3-specific probe. The breakpoint regions were defined by FISH using YAC probes from 3q and 12p chromosomal regions. Interestingly, partial trisomy of 3q has been detected in a previously reported JMML case, consequent to the presence of a der(15)t(3;15)(q13.1;q26). The involvement of a similar chromosome 3 rearrangement in these two JMML cases suggests the hypothesis that either the resulting duplication of some gene/s on 3q or the loss of heterozygosity (LOH) of some gene/s on 3p may be involved in one of the steps leading to JMML. On the other hand, it cannot be ruled out that the relevant mutation in our case might be consequent to the particular breakpoints at bands 3q21 approximately 22 and 12p13.3, that may alter the structure and/or expression of the involved gene/s.
Assuntos
Aberrações Cromossômicas/genética , Leucemia Mielomonocítica Crônica/genética , Transtornos Mieloproliferativos/genética , Proteínas Repressoras , Transtornos Cromossômicos , Mapeamento Cromossômico , Cromossomos Humanos Par 12 , Cromossomos Humanos Par 3 , Proteínas de Ligação a DNA/genética , Humanos , Hibridização in Situ Fluorescente , Proteínas Proto-Oncogênicas c-ets , Fatores de Transcrição/genética , Translocação Genética , Trissomia , Variante 6 da Proteína do Fator de Translocação ETSRESUMO
The t(1;19) is the most frequent recurring chromosomal translocation in childhood acute lymphoblastic leukaemia (ALL). In most cases typical chimaeric E21-PBX1 transcripts are expressed as a consequence of this rearrangement, allowing the molecular detection of the t(1;19) at the RNA level. This translocations has been associated with a poor clinical outcome, although intensified chemotherapy has been reported to nullify its adverse prognostic impact. We therefore used reverse transcriptase/polymerase chain reaction (RT-PCR) to detect residual leukaemic cells at successive times during treatment and to monitor the response to chemotherapy in six t(1;19)-positive ALL pediatric patients. Five of these patients rapidly achieved molecular remission and no evidence of minimal residual disease (MRD) was found in the remission bone marrows beyond the third month of treatment. One patient still displayed residual leukaemic cells at the end of therapy, although she has been in continuous complete clinical remission (CCR) for 84 months. However, this patient is peculiar in our series in that two different types of chimaeric E2A-PBX1 transcripts were expressed in her leukaemic cells, only one being detectable in remission.
Assuntos
Cromossomos Humanos Par 19 , Cromossomos Humanos Par 1 , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Translocação Genética , Antineoplásicos/uso terapêutico , Southern Blotting , Criança , Pré-Escolar , Quimera , Feminino , Seguimentos , Humanos , Cariotipagem , Masculino , Neoplasia Residual , Reação em Cadeia da Polimerase/métodos , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , DNA Polimerase Dirigida por RNARESUMO
Four foci (type II or type III) of transformed cells, isolated from the murine line C3H10T1/2 after exposure to proton radiations, were expanded and cytogenetically examined. While the overall numerical chromosome distributions were similar, there were some differences between the various cell lines with regard to the presence and frequency of specific-marker chromosomes and to the colony-forming efficiency in soft-agarose medium. No association between any of these markers and the transformed phenotype could be established. However, in the line F4, derived from a type II focus, numerous double-minute chromosomes (DM) were observed after passage 22, and the phenomenon became more pronounced in the subclone C2. The finding of DMs in radiation-transformed cells is unusual. The DMs were observed in long-term subcultures, and in one of them they were partially replaced by a homogeneously staining chromosome region (HSR). DNAs from transformed cells of the line F4 and subclone C2 was digested with restriction enzymes and analyzed by Southern blotting with probes for seven oncogenes commonly amplified in cancer cells (c-myc, N-myc, N-ras, Ki-ras, Ha-ras, c-myb, c-abl) and with probes for the mouse MHC class I region. None of the regions tested was structurally altered or amplified in these transformed cells. The origin of the genetic material carried by DMs or homogeneously staining intrachromosomal regions (HSR) in cells of the line F4 and subclone C2, where it is believed to provide a selective advantage for in vitro growth, remains unknown.