RESUMEN
The presence of actin in the nucleus has been well established, and several studies have implicated nuclear actin in transcriptional regulation. Neuronal Wiskott-Aldrich syndrome protein (N-WASP) is a member of the WASP family of proteins; these proteins function in the cytoplasm as key regulators of cortical actin filament. Interestingly, N-WASP has also been observed in the nucleus. However, a potential nuclear function for N-WASP has not been established. Here, we report the identification of nuclear N-WASP within a large nuclear-protein complex containing PSF-NonO (polypyrimidine-tract-binding-protein-associated splicing factor-non-Pou-domain octamer-binding protein/p54(nrb)), nuclear actin and RNA polymerase II. The PSF-NonO complex is involved in the regulation of many cellular processes, such as transcription, RNA processing, DNA unwinding and repair. We demonstrate that the interaction of N-WASP with the PSF-NonO complex can couple N-WASP with RNA polymerase II to regulate transcription. We also provide evidence that the potential function of N-WASP in promoting polymerization of nuclear actins has an important role in this process. Based on these results, we propose a nuclear function for N-WASP in transcriptional regulation.
Asunto(s)
Actinas/biosíntesis , Núcleo Celular/metabolismo , ARN Polimerasa II/metabolismo , Elementos Reguladores de la Transcripción/genética , Transcripción Genética/genética , Proteína Neuronal del Síndrome de Wiskott-Aldrich/metabolismo , Citoesqueleto de Actina/genética , Citoesqueleto de Actina/metabolismo , Actinas/genética , Núcleo Celular/genética , Proteínas de Unión al ADN , Humanos , Sustancias Macromoleculares/metabolismo , Proteínas Asociadas a Matriz Nuclear/genética , Proteínas Asociadas a Matriz Nuclear/metabolismo , Factores de Transcripción de Octámeros/genética , Factores de Transcripción de Octámeros/metabolismo , Factor de Empalme Asociado a PTB , Polímeros/metabolismo , ARN Polimerasa II/genética , ARN Mensajero/biosíntesis , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Proteína Neuronal del Síndrome de Wiskott-Aldrich/genéticaRESUMEN
Sangre de grado is an ethnomedicinal red tree sap obtained from Croton spp. that is used to treat gastrointestinal ulcers, cancer and to promote wound healing. To evaluate the potential role of sangre de grado (SdG) in cancer we examined its effects on human cancer cells, AGS (stomach), HT29 and T84 (colon). Viability of cells treated with SdG (10-200 microg/ml) decreased (P<0.01) in a dose dependent manner measured over a 24-h period. Cell proliferation at 48 h decreased (P<0.01) in all cells treated with SdG (>100 microg/ml). When cells in suspension were treated with SdG (100 microg/ml) cell adherence was severely compromised (>85%). Cells treated with SdG (100 microg/ml) underwent apoptosis as detected by nucleus condensation and DNA fragmentation determined by ELISA, and flow cytometry. Morphological changes as assessed by acridine orange. These effects were similar to that observed with Taxol (30 microM). A significant alteration of microtubular architecture was equally observed in both stomach and colon cancer cells exposed to SdG (100 microg/ml). The induction of apoptosis and microtubule damage in AGS, HT29 and T84 cells suggest that sangre de grado should be evaluated further as a potential source of anti-cancer agents.
Asunto(s)
Antineoplásicos/farmacología , Apoptosis , Croton , Extractos Vegetales/farmacología , Adhesión Celular/efectos de los fármacos , División Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Neoplasias Gastrointestinales , Humanos , Microscopía Fluorescente , Microtúbulos/efectos de los fármacos , Microtúbulos/ultraestructura , Células Tumorales CultivadasRESUMEN
The actin-related protein 2/3 (Arp2/3) complex is a crucial actin polymerization nucleator and is localized to the leading protrusions of migrating cells. However, how the multiprotein complex is targeted to the protrusions remains unknown. Here, we demonstrate that mRNAs for the seven subunits of the Arp2/3 complex are localized to the protrusions in fibroblasts, supporting a hypothesis that the Arp2/3 complex is targeted to its site of function by mRNA localization. Depletion of serum from culture medium inhibits Arp2/3-complex mRNA localization to the protrusion, whereas serum stimulation leads to significant mRNA localization within 30 minutes. The effect of serum suggests that Arp2/3-complex mRNA localization is a cellular response to extracellular stimuli. The localization of the Arp2/3 complex mRNAs is dependent on both actin filaments and microtubules, because disruption of either cytoskeletal system (with cytochalasin D and colchicine, respectively) inhibited the localization of all seven subunit mRNAs. In addition, myosin inhibitors significantly inhibit Arp2 mRNA localization in chicken embryo fibroblasts, suggesting a myosin motor dependent mechanism for Arp2/3-complex mRNA localization.