RESUMO
The p14(ARF) (ARF) tumour suppressor plays an important role in the cellular response to oncogene activation. In this report, we demonstrate an interaction between ARF and DAXX, a highly conserved protein with identified roles in the regulation of gene expression. HDM2 was shown to interact with each of ARF and DAXX upon upregulation of expression as well as at lower expression levels following transfection of ARF and DAXX. Through immunofluorescence analysis, we observed that endogenous ARF and DAXX colocalize both to nucleoli and to nuclear bodies in cell lines that co-express both proteins. Similar results were obtained upon co-transfection of ARF and DAXX. Co-expression of ARF and DAXX was further found to inhibit ARF-mediated HDM2 sumoylation and to induce sumoylation and ubiquitination of DAXX itself, implicating DAXX as a substrate of ARF-mediated post-translational events. We also observed induction of p53 sumoylation in the presence of ARF and DAXX, an effect that was inhibited by upregulation of HDM2 expression. In summary, we have identified DAXX as a novel ARF binding partner and substrate of ARF-mediated sumoylation and suggest that DAXX acts as a modifier of both p53-dependent and p53-independent ARF function.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Proto-Oncogênicas c-mdm2/metabolismo , Proteína Supressora de Tumor p14ARF/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/análise , Proteínas Adaptadoras de Transdução de Sinal/química , Animais , Sítios de Ligação , Linhagem Celular , Nucléolo Celular/química , Estruturas do Núcleo Celular/química , Proteínas Correpressoras , Humanos , Chaperonas Moleculares , Proteínas Nucleares/análise , Proteínas Nucleares/química , Proteínas Repressoras/metabolismo , Proteína SUMO-1/metabolismo , Proteína Supressora de Tumor p14ARF/análise , Proteína Supressora de Tumor p14ARF/química , Técnicas do Sistema de Duplo-Híbrido , UbiquitinaçãoRESUMO
Organization of the central nervous system during embryonic development is an intricate process involving a host of molecular players. The Drosophila segmentation genes, sloppy paired (slp) 1/2 have been shown to be necessary for development of a neuronal precursor cell subtype, the NB4-2 cells. Here, we show that slp1/2 also have roles in regulating glial cell fates. Using slp1/2 loss-of-function mutants, we show an increase in glial cell markers, glial cells missing (gcm) and reversed polarity. In contrast, misexpression of either slp1 or slp2 causes downregulation of glial cell-specific genes and alters the fate of glial and neuronal cells. Furthermore, we demonstrate that Slp1 and its mammalian ortholog, Foxg1, inhibit Gcm transcriptional activity as well as bind Gcm. Taken together, these data show that Slp1/Foxg1 regulate glial cell fates by inhibiting Gcm function.
Assuntos
Sistema Nervoso Central/embriologia , Proteínas de Ligação a DNA/metabolismo , Proteínas de Drosophila/genética , Drosophila melanogaster/embriologia , Neuroglia/metabolismo , Células-Tronco/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Animais , Células COS , Diferenciação Celular/genética , Linhagem da Célula/genética , Sistema Nervoso Central/citologia , Sistema Nervoso Central/metabolismo , Chlorocebus aethiops , Proteínas de Ligação a DNA/antagonistas & inibidores , Proteínas de Ligação a DNA/genética , Regulação para Baixo/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Desenvolvimento Embrionário/genética , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/genética , Mutação/genética , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Neuroglia/citologia , Neurônios/citologia , Neurônios/metabolismo , Ligação Proteica/genética , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Células-Tronco/citologia , Fatores de Transcrição/antagonistas & inibidoresRESUMO
PROLIFERATIVE CUES TRIGGER a complex series of molecular signaling events in cells. Early in the cell cycle, cells are faced with an important decision that affects their fate. They either initiate a round of replication or they withdraw from cell division. Passage through the restriction point, or "point of no return," marks cellular commitment to a new round of division. Genetic mutations that predispose individuals to tumorigenesis often affect pathways that influence cellular proliferation. Many of the mutated genes give rise to molecules that are no longer able to appropriately regulate the mammalian cell cycle; the end result is neoplasia. In this review, the critical elements that permit cell cycle progression and the positive and negative regulators that affect the process are reviewed.
