RESUMO
We have previously identified NPDC-1, a neural factor involved in the control of proliferation and differentiation, and we have shown that the stable introduction of NPDC-1 into transformed cells down-regulates cell proliferation both by increasing the generation time and by suppressing transformed properties. The data presented here indicate that, in vitro, NPDC-1 is able to interact with the transcription factor E2F-1 and some cell cycle proteins, such as D-cyclins and cdk2. In addition, two-hybrid experiments in mammalian cells show that the interaction between NPDC-1 and E2F-1 can also occur in vivo. This interaction reduces the binding of E2F-1 to DNA and its transcriptional activity. Taken together, the data suggest that NPDC-1 could influence cell cycle progression and neural differentiation through its association with E2F-1.
Assuntos
Proteínas de Transporte , Proteínas de Ligação a DNA/metabolismo , DNA/metabolismo , Proteínas do Tecido Nervoso/fisiologia , Fatores de Transcrição/metabolismo , Transcrição Gênica/fisiologia , Animais , Sítios de Ligação , Proteínas de Ciclo Celular/metabolismo , DNA/antagonistas & inibidores , DNA/genética , Proteínas de Ligação a DNA/antagonistas & inibidores , Proteínas de Ligação a DNA/genética , Fatores de Transcrição E2F , Fator de Transcrição E2F1 , Genes Reporter/genética , Glutationa Transferase/genética , Humanos , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Mapeamento de Peptídeos , Regiões Promotoras Genéticas , Coelhos , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/farmacologia , Proteína 1 de Ligação ao Retinoblastoma , Fator de Transcrição DP1 , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/genética , Transcrição Gênica/efeitos dos fármacos , TransfecçãoRESUMO
Most of the genes involved in the regulation of proliferation and differentiation of neural cells remain to be identified. With the aim of identifying such genes, the strategy we used was to search for cDNAs which both hybridized with helix-loop-helix degenerated probes and corresponded to RNAs expressed preferentially when neural precursor cells become growth-arrested and began to differentiate. This led to the isolation of NPDC-1 cDNA and then of the genomic sequence. We observed that NPDC-1 is specially expressed in the nervous system and that the transfection of neural precursors with NPDC-1 cDNA results in the inhibition of cell proliferation. Moreover, the stable introduction of NPDC-1 into transformed cells downregulates cell proliferation both by increasing the generation time and by suppressing transformed and tumorigenic properties. We verified that these biological effects were reversed by NPDC-1 anti-sense oligonucleotides. Then we have examined the expression of NPDC-1 mRNA along mouse development and the interactions of the NPDC-1 protein with cell cycle regulatory proteins. The results showed that NPDC-1 mRNA begins to be expressed in a variety of neural structures, when the precursors enter their terminal differentiation. In addition, we have observed that NPDC-1 protein interacts with the transcription factor E2F-1. As a whole, the present results show that NPDC-1 down-regulates the proliferation of neural precursors, is able to suppress oncogenic transformation, is involved in the terminal differentiation of neural cells and acts probably through interactions with E2F-1.
