ABSTRACT
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.
Subject(s)
Carrier Proteins , DNA-Binding Proteins/metabolism , DNA/metabolism , Nerve Tissue Proteins/physiology , Transcription Factors/metabolism , Transcription, Genetic/physiology , Animals , Binding Sites , Cell Cycle Proteins/metabolism , DNA/antagonists & inhibitors , DNA/genetics , DNA-Binding Proteins/antagonists & inhibitors , DNA-Binding Proteins/genetics , E2F Transcription Factors , E2F1 Transcription Factor , Genes, Reporter/genetics , Glutathione Transferase/genetics , Humans , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , Peptide Mapping , Promoter Regions, Genetic , Rabbits , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/pharmacology , Retinoblastoma-Binding Protein 1 , Transcription Factor DP1 , Transcription Factors/antagonists & inhibitors , Transcription Factors/genetics , Transcription, Genetic/drug effects , TransfectionABSTRACT
We have previously identified NPDC-1, a gene specifically expressed in neural cells and involved in the control of cell proliferation and differentiation. In the present study, we have investigated the expression of this gene during mouse development and the interactions of the NPDC-1 protein with cell cycle regulatory proteins. The data show that NPDC-1 mRNA begins to be expressed in a variety of neural structures when the precursors enter into their terminal differentiation. They also indicate that in adult brain, the expression patterns of NPDC-1 and E2F-1 mRNA largely overlap. In addition, the NPDC-1 protein is able to interact directly with the transcription factor E2F-1 that participates in the regulation of the cell cycle, cell survival, and apoptosis. The present results suggest that NPDC-1 might be involved in the terminal differentiation and survival of neural cells and might act through interactions with E2F-1.
Subject(s)
Carrier Proteins , Cell Cycle Proteins/biosynthesis , DNA-Binding Proteins , Nerve Tissue Proteins/biosynthesis , Neurons/metabolism , Transcription Factors/biosynthesis , Animals , Blotting, Northern , Cell Differentiation/physiology , Cell Division/physiology , Cell Line , Cells, Cultured , E2F Transcription Factors , E2F1 Transcription Factor , Female , Immunohistochemistry , In Situ Hybridization , Mice , Neurons/physiology , PC12 Cells , Pregnancy , RNA, Messenger/biosynthesis , Rats , Retinoblastoma-Binding Protein 1 , Transcription Factor DP1ABSTRACT
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.
