RESUMO
The TFPT/FB1 gene was identified because of its involvement in childhood pre-B acute lymphoblastic leukaemia (ALL). Although its specific function is still unclear, Tfpt has been implicated in cell proliferation and induction of programmed cell death (PCD). Given the critical role of PCD in leukemogenesis, we have investigated the responsiveness of different cell lines to TFPT over expression and the consequent induction of PCD by proliferation kinetic analysis, immunolocalization and TUNEL assay. We have also tested the involvement of factors implicated in cell cycle progression and apoptosis, i.e. caspases, p53, Cdc2. Our results indicate that over expression of TFPT promotes caspase 9-dependent apoptosis, nevertheless the apoptotic cascade is engaged only in culture conditions sustaining cell proliferation and different cell lines display differential responsiveness to TFPT induced apoptosis Although p53 is a main regulator of apoptosis in mammalian cells, the Tfpt induced apoptosis appears p53-independent. These results are discussed relatively to the role played by TFPT in leukemogenesis.
Assuntos
Apoptose , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Fatores de Transcrição TCF/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Regulação para Cima , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Caspases/metabolismo , Contagem de Células , Proliferação de Células , Ativação Enzimática , Expressão Gênica , Células HeLa , Humanos , Marcação In Situ das Extremidades Cortadas , Cinética , Camundongos , Modelos Biológicos , Células NIH 3T3 , Ligação Proteica , Proteína 1 Semelhante ao Fator 7 de TranscriçãoRESUMO
The yeast SDA1 gene was reported to play a critical role in G(1) events and to be involved in 60S ribosome biogenesis. Although the basic cellular mechanisms appear conserved from yeast to man, the human genes may have more diversified functions. In this view we obtained the first experimental evidences about the human ortholog of the yeast SDA1, i.e., hSDA. The gene is localized at the chromosomal region 4q21 and encodes for a 627a.a. long protein highly homologous to the yeast Sda1. Subcellular localization experiments indicate that the human protein behaves similarly to nucleolar proteins involved in rRNA processing machinery but not in RNA PolI transcriptional events. hSda appears localized in the granular component of the nucleolus and in the nucleoplasm, which is consistent with a role in early-intermediate steps of ribosome biogenesis. hSDA appears preferentially expressed in fetal tissues, pinpointing its role during development. Different expression levels in different tumor cell lines might suggest that the gene is involved also in tumorigenesis. However our preliminary results indicate that hSDA does not behave like a proapoptotic gene and its involvement in tumorigenesis is still to be clarified.