Asunto(s)
Proteínas de Unión al ADN/genética , Leucemia Promielocítica Aguda/genética , Mielopoyesis/genética , Proteínas Nucleares/genética , Proteínas de Fusión Oncogénica/genética , Transcripción Genética , Proteínas Supresoras de Tumor/genética , Secuencia de Bases , Línea Celular Tumoral , Humanos , Leucemia Promielocítica Aguda/metabolismo , Leucemia Promielocítica Aguda/patología , Datos de Secuencia Molecular , Proteínas de Fusión Oncogénica/antagonistas & inhibidores , Proteínas de Fusión Oncogénica/metabolismo , Regiones Promotoras Genéticas , Tretinoina/farmacologíaRESUMEN
Hepatitis C virus (HCV) is the major causative viral agent of cirrhosis and hepatocarcinoma (HCC). HCV core protein affects cell homeostasis, playing an important role in viral pathogenesis of HCC. We investigate the effects of HCV core protein expression on cell growth in HCC cell lines. Cell cycle distribution analysis of HepG2 polyclonal core positive cells reveals a peculiar accumulation of cells in G2/M phase. Different pathways mediate G2/M arrest: such as p53 and double strand RNA protein kinase (PKR). Flow cytometry in p53-null cells demonstrates that p53 plays only a marginal role in inducing HCV core-dependent G2/M phase accumulation that seems to be significantly affected by the functional inactivation of PKR. HCC core positive cells are characterized by a significant PKR phosphorylation in Thr 446 residue, which leads deregulation of mitosis. Moreover, we observe that the overexpression of the viral protein induces an upregulation of PKR activity, which does not correlate with an increased eIF-2 phosphorylation. This uncommon behavior of PKR suggests that its activation by HCV core protein could involve alternative PKR-dependent pathways, implicated in core-dependent G2/M accumulation. The described biological effects of HCV core protein on cell cycle could be an additional viral mechanism for both HCV resistance to interferon (IFN) and HCC HCV-related pathogenesis.
Asunto(s)
Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patología , División Celular , Fase G2 , Fosfotreonina/metabolismo , Proteínas del Núcleo Viral/metabolismo , eIF-2 Quinasa/metabolismo , Animales , Carcinoma Hepatocelular/genética , Línea Celular , Hepacivirus , Humanos , Ratones , Ratones Noqueados , Fosforilación , Proteína p53 Supresora de Tumor/deficiencia , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismo , Proteínas del Núcleo Viral/genética , eIF-2 Quinasa/química , eIF-2 Quinasa/genéticaRESUMEN
Increasing evidence indicates that the nm23 genes, initially documented as suppressors of metastasis progression, are involved in normal development and differentiation. We have shown previously that the murine nm23 gene enhances pheochromocytoma PC12 cells responsiveness to NGF by accelerating cell growth arrest and neurite outgrowth. The present study was aimed at elucidating the mechanisms by which nm23 controls cell proliferation and promotes neuronal differentiation. We demonstrated that nm23 modulates the expression of the Rb2/p130 gene, a negative regulator of cell cycle progression also implicated in the maintenance of the differentiated state. Furthermore, we showed that nm23-H1 mutants, defective in inhibiting the invasive phenotype, downregulate Rb2/p130 expression and inhibit NGF-induced PC12 cell differentiation. In synthesis, our results provide first evidence of interplay between the nm23 and the Rb2/p130 genes in driving PC12 cells neuronal differentiation and suggest that the antimetastatic and the differentiative nm23 functions can have similar features.
