RESUMO
We used DNA microarray screening to identify Ckap2 (cytoskeleton associated protein 2) as a novel p53 target gene in a mouse erythroleukemia cell line. DNA damage induces human and mouse CKAP2 expression in a p53-dependent manner and p53 activates the Ckap2 promoter. Overexpressed Ckap2 colocalizes with and stabilizes microtubules. In p53-null cells, overexpression of Ckap2 induces tetraploidy with aberrant centrosome numbers, suggesting disturbed mitosis and cytokinesis. In p53-competent cells, Ckap2 does not induce tetraploidy but activates p53-mediated cell cycle arrest and apoptosis. Our data suggest the existence of a functional positive feedback loop in which Ckap2 activates the G1 tetraploidy checkpoint and prevents aneuploidy.
Assuntos
Aneuploidia , Proteínas do Citoesqueleto/genética , Leucemia Eritroblástica Aguda/genética , Proteína Supressora de Tumor p53/genética , Animais , Apoptose/genética , Ciclo Celular/genética , Centrossomo/fisiologia , Proteínas do Citoesqueleto/metabolismo , Células HCT116 , Humanos , Leucemia Eritroblástica Aguda/patologia , Camundongos , Microtúbulos/metabolismo , Células NIH 3T3 , Análise de Sequência com Séries de Oligonucleotídeos , Regiões Promotoras Genéticas , Ativação TranscricionalRESUMO
The immediate-early gene Nur77, which encodes an orphan nuclear receptor, is rapidly induced by various stress stimuli, including tumor necrosis factor (TNF). Nur77 has been implicated in mediating apoptosis, particularly in T cells and tumor cells. We report here that Nur77 can play a role in antagonizing apoptosis in TNF signaling. Nur77 expression is strongly induced by TNF. Interestingly, unlike most antiapoptotic molecules, this induced expression of Nur77 is largely independent of NF-kappa B. Ectopic expression of Nur77 can protect wild-type, TRAF2-/-, and RelA-/- cells from apoptosis induced by TNF, whereas expression of a dominant-negative form of Nur77 (DN-Nur77) accelerates TNF-mediated cell death in the mutant cells. In mouse embryonic fibroblasts, Nur77 remains in the nucleus in response to TNF and is not translocated to the mitochondria, where it was reported to mediate apoptosis. Our results suggest that Nur77 is a survival effector protein in the context of TNF-mediated signaling.