ABSTRACT
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.
Subject(s)
Apoptosis , Drosophila Proteins/metabolism , Drosophila melanogaster/metabolism , E2F Transcription Factors/metabolism , Mitochondria/pathology , Osteosarcoma/pathology , Trans-Activators/metabolism , Animals , Animals, Genetically Modified , Blotting, Western , Bone Neoplasms/genetics , Bone Neoplasms/metabolism , Bone Neoplasms/pathology , Cell Cycle , Cell Proliferation , Chromatin Immunoprecipitation , DNA Damage/genetics , DNA Damage/radiation effects , Drosophila Proteins/genetics , Drosophila melanogaster/genetics , Drosophila melanogaster/growth & development , E2F Transcription Factors/genetics , Fluorescent Antibody Technique , Gamma Rays , Humans , Immunoenzyme Techniques , Mitochondria/metabolism , Mitochondria/radiation effects , Osteosarcoma/genetics , Osteosarcoma/metabolism , Phenotype , Trans-Activators/genetics , Transcription Factors , Tumor Cells, CulturedABSTRACT
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.
