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
Juvenile myelomonocytic leukemia (JMML) is a rare myeloproliferative disease of early childhood, that is peculiarly characterized by the ability of bone marrow progenitors to spontaneously proliferate in vitro, giving rise to granulocyte-macrophage colonies. Although the genetic alteration/s leading to JMML development are still unclear, several lines of evidence indicate that the JMML initiating cell (JMML-IC) may belong to the pool of early stem-like hematopoietic progenitors. Increased EVI-1 gene expression has been detected in a number of myeloproliferative disorders including MDS, AML, blast crisis of CML, and more recently in the peripheral blood of some JMML patients. In order to investigate the nature of the cells expressing EVI-1 in JMML patients, we analyzed its expression in CFU-GM obtained from bone marrow and peripheral blood as well as from highly purified CD34+ progenitors. Normal CFU-GM obtained both from bone marrow mononuclear cells and from highly purified CD34+ cells were also analyzed. Overall, our results suggest that the EVI-1 gene may be normally expressed in early hematopoietic progenitor cells and that in JMML patients an expansion of the EVI-1 positive cell population can be revealed within the clonogenic progenitor pool.