RESUMO
Acetylation is thought to be a key event for p53 activation. We demonstrate that p14ARF-induced senescence of human mammary epithelial cells (MEC) is associated with p53 acetylation and requires hAda3, a component of histone acetyltransferase complexes and a p53 transcriptional coactivator. Expression of the N-terminal domain of hAda3 that binds p53 but not p300 blocked p14ARF-induced p53 acetylation and protected MECs from senescence. Consistent with these findings, the human papillomavirus 16 E6 mutant Y54D, which selectively targets hAda3 but not p53 for degradation and protects MECs from p14ARF-induced senescence, inhibited p53 acetylation. In H1299 cells, hAda3 overexpression increased p300-mediated p53 acetylation, which conversely decreased following small interfering RNA (siRNA) knockdown of hAda3. Moreover, depletion of hAda3 by siRNA inhibited endogenous p53 acetylation and accumulation of p21cip1 in response to ectopic p14ARF. These studies reveal that, in addition to its known ability to inhibit Mdm2-mediated p53 degradation, p14ARF signals through hAda3 to stimulate p53 acetylation and the induction of cell senescence.
Assuntos
Senescência Celular/fisiologia , Fatores de Transcrição/metabolismo , Proteína Supressora de Tumor p14ARF/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Acetilação , Linhagem Celular Tumoral , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Células Epiteliais/metabolismo , Humanos , Interferência de RNA , Telomerase/genética , Telomerase/metabolismo , Fatores de Transcrição/genética , Proteína Supressora de Tumor p14ARF/genética , Proteína Supressora de Tumor p53/genéticaRESUMO
Recent data suggest that additional factors, other than UV radiation, are involved in the etiology of non-melanoma skin cancer. These include alterations in the tumor suppressor genes, p53, p16$L*I*U$LINK4a$L*I$L/CDKN2A, p21$L*I*U$LWAF1/CIP1$L*I$L and the PTCH gene, as well as cytokines. Papillomavirus infections have been implicated in the etiology of non-melanoma skin cancer. The interaction of tumor suppressor genes and cytokines with the oncoproteins of high-risk mucosal HPV types have been studied in detail, but very little is known about the cutaneous HPV types. We have studied the effect of UV radiation on the URRs of HPV 1, 2, 3, 5, 7, 20, 23, 27, 38, 41, and 77. Neither the CAT-expression and promoter activity of these HPV types, nor presence or absence of wild-type or mutated p53 in the cell lines used, could be related to the DNA sequence homology between the different HPV types or their biological behavior.
