RESUMO
Elevation of p16(INK4a) has been described as an important mechanism for hydrogen peroxide (H2O2)-induced replicative senescence. However, the mechanisms underlying remain unknown. In this study, we demonstrate an important role of RNA-binding protein AUF1-mediated mRNA turnover in H2O2-induced p16(INK4a) expression. The induction of p16 by H2O2 was accompanied with declined cytoplasmic AUF1 level. Accordingly, exposure of cells to H2O2 remarkably reduced the binding of AUF1 to p16 3'UTR and increased the half-life of an EGFP-p16-3'UTR chimeric transcript. In AUF1-silenced cells, the effect of H2O2 on p16 induction was abolished. Furthermore, in cells co-transfected with vectors expressing AUF1s, treatment with H2O2 failed to significantly reduce the expression of AUF1 and subsequently elevate the levels of p16. Moreover, HeLa cells overexpressing AUF1s were resistant to H2O2-induced senescence. Our results indicate that AUF1 is critical for H2O2-induced p16 expression and cellular senescence.
Assuntos
Inibidor p16 de Quinase Dependente de Ciclina/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo D/metabolismo , Peróxido de Hidrogênio/farmacologia , Regiões 3' não Traduzidas/genética , Senescência Celular/efeitos dos fármacos , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Células HeLa , Ribonucleoproteína Nuclear Heterogênea D0 , Humanos , Ligação Proteica/efeitos dos fármacos , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
Twenty Israeli children diagnosed as having Attention Deficit Hyperactivity Disorder (ADHD) participated in the study. The study used a double-blind, cross-over, placebo-control design, in which each child received a three-week treatment of methylphenidate (MPH), and a three-week treatment with a placebo. Their teachers completed the Conners' Teacher Rating Scale (CTRS) along with ratings of other variables prior to the beginning of the study and during the two treatment periods. The subjects were tested on a specially designed battery of both cognitive and personality tests at the end of each treatment period. The results showed significant differences between ratings of children's behavior in pretest and subsequent placebo and MPH treatment periods. Comparison of the MPH and placebo treatment revealed no differences in any of the measures assessing cognitive ability and personality characteristics.
