RESUMO
E2F/DP transcription factors regulate cell proliferation and apoptosis. Here, we investigated the mechanism of the resistance of Drosophila dDP mutants to irradiation-induced apoptosis. Contrary to the prevailing view, this is not due to an inability to induce the apoptotic transcriptional program, because we show that this program is induced; rather, this is due to a mitochondrial dysfunction of dDP mutants. We attribute this defect to E2F/DP-dependent control of expression of mitochondria-associated genes. Genetic attenuation of several of these E2F/DP targets mimics the dDP mutant mitochondrial phenotype and protects against irradiation-induced apoptosis. Significantly, the role of E2F/DP in the regulation of mitochondrial function is conserved between flies and humans. Thus, our results uncover a role of E2F/DP in the regulation of mitochondrial function and demonstrate that this aspect of E2F regulation is critical for the normal induction of apoptosis in response to irradiation.
Assuntos
Apoptose , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Fatores de Transcrição E2F/metabolismo , Mitocôndrias/patologia , Osteossarcoma/patologia , Transativadores/metabolismo , Animais , Animais Geneticamente Modificados , Western Blotting , Neoplasias Ósseas/genética , Neoplasias Ósseas/metabolismo , Neoplasias Ósseas/patologia , Ciclo Celular , Proliferação de Células , Imunoprecipitação da Cromatina , Dano ao DNA/genética , Dano ao DNA/efeitos da radiação , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/crescimento & desenvolvimento , Fatores de Transcrição E2F/genética , Imunofluorescência , Raios gama , Humanos , Técnicas Imunoenzimáticas , Mitocôndrias/metabolismo , Mitocôndrias/efeitos da radiação , Osteossarcoma/genética , Osteossarcoma/metabolismo , Fenótipo , Transativadores/genética , Fatores de Transcrição , Células Tumorais CultivadasRESUMO
Epigenetic regulation underlies the robust changes in gene expression that occur during development. How precisely epigenetic enzymes contribute to development and differentiation processes is largely unclear. Here we show that one of the enzymes that removes the activating epigenetic mark of trimethylated lysine 4 on histone H3, lysine (K)-specific demethylase 5A (KDM5A), reinforces the effects of the retinoblastoma (RB) family of transcriptional repressors on differentiation. Global location analysis showed that KDM5A cooccupies a substantial portion of target genes with the E2F4 transcription factor. During ES cell differentiation, knockout of KDM5A resulted in derepression of multiple genomic loci that are targets of KDM5A, denoting a direct regulatory function. In terminally differentiated cells, common KDM5A and E2F4 gene targets were bound by the pRB-related protein p130, a DREAM complex component. KDM5A was recruited to the transcription start site regions independently of E2F4; however, it cooperated with E2F4 to promote a state of deepened repression at cell cycle genes during differentiation. These findings reveal a critical role of H3K4 demethylation by KDM5A in the transcriptional silencing of genes that are suppressed by RB family members in differentiated cells.
