RESUMO
Nuclear lamins are the main components of the nuclear lamina at the nuclear periphery, providing mechanical support to the nucleus. However, recent findings suggest that lamins also reside in the nuclear interior, as a distinct and dynamic pool with critical roles in transcriptional regulation. In our work we found a functional and evolutionary conserved crosstalk between Lamin A/C and the Polycomb group (PcG) of proteins, this being required for the maintenance of the PcG repressive functions. Indeed, Lamin A/C knock-down causes PcG foci dispersion and defects in PcG-mediated higher order structures, thereby leading to impaired PcG mediated transcriptional repression. By using ad-hoc algorithms for image analysis and PLA approaches we hereby show that PcG proteins are preferentially located in the nuclear interior where they interact with nucleoplasmic Lamin A/C. Taken together, our findings suggest that nuclear components, such as Lamin A/C, functionally interact with epigenetic factors to ensure the correct transcriptional program maintenance.
Assuntos
Evolução Molecular , Lamina Tipo A/metabolismo , Proteínas do Grupo Polycomb/metabolismo , Transporte Ativo do Núcleo Celular , Diferenciação Celular , Núcleo Celular/metabolismo , Células HEK293 , Humanos , Mioblastos/citologia , Ligação ProteicaRESUMO
Apaf1 is a key regulator of the mitochondrial intrinsic pathway of apoptosis, as it activates executioner caspases by forming the apoptotic machinery apoptosome. Its genetic regulation and its post-translational modification are crucial under the various conditions where apoptosis occurs. Here we describe Ku70/86, a mediator of non-homologous end-joining pathway of DNA repair, as a novel regulator of Apaf1 transcription. Through analysing different Apaf1 promoter mutants, we identified an element repressing the Apaf1 promoter. We demonstrated that Ku70/86 is a nuclear factor able to bind this repressing element and downregulating Apaf1 transcription. We also found that Ku70/86 interaction with Apaf1 promoter is dynamically modulated upon DNA damage. The effect of this binding is a downregulation of Apaf1 expression immediately following the damage to DNA; conversely, we observed Apaf1 upregulation and apoptosis activation when Ku70/86 unleashes the Apaf1-repressing element. Therefore, besides regulating DNA repair, our results suggest that Ku70/86 binds to the Apaf1 promoter and represses its activity. This may help to inhibit the apoptosome pathway of cell death and contribute to regulate cell survival.
Assuntos
Antígenos Nucleares/metabolismo , Fator Apoptótico 1 Ativador de Proteases/genética , Dano ao DNA , Reparo do DNA , Proteínas de Ligação a DNA/metabolismo , Animais , Antígenos Nucleares/química , Morte Celular/efeitos dos fármacos , Linhagem Celular , Dano ao DNA/genética , Reparo do DNA/efeitos dos fármacos , Reparo do DNA/genética , Proteínas de Ligação a DNA/química , Etoposídeo/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Peróxido de Hidrogênio/farmacologia , Autoantígeno Ku , Camundongos , Regiões Promotoras Genéticas/genética , Ligação Proteica/efeitos dos fármacos , Proteínas Repressoras/metabolismo , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Transcrição Gênica/efeitos dos fármacosRESUMO
During cell differentiation or metabolic switch, cells undergo profound changes in gene expression. These events are accompanied by complex modifications of chromosomal components and nuclear structures, including covalent modifications of DNA and chromatin up to topological reorganization of chromosomes and genes in the nucleus. To various extents, all these levels of organization appear to contribute to the stability and heritability of transcription programmes and define what is meant as the epigenomic level of gene regulation. Indeed, damage or perturbation of epigenome components may lead to deviations from a determined cellular programme, resulting in severe developmental disorders and tumour progression. Most recent data also suggest that tissue regeneration and transdifferentiation are controlled by epigenetic functions. Thus, the epigenome provides the molecular basis for the preservation and also for the plasticity of cell identity.
Assuntos
Regulação da Expressão Gênica , Genoma , Animais , Núcleo Celular/genética , Núcleo Celular/ultraestrutura , Cromatina/genética , Cromatina/fisiologia , Cromossomos/ultraestrutura , DNA/química , DNA/genética , Dimerização , Código Genético , Histonas/química , Histonas/genética , Humanos , Modelos Moleculares , Conformação de Ácido Nucleico , Nucleossomos/genéticaRESUMO
A small 78 codon ORF, named HTL1 (Chen et al., unpublished results), situated between loci MAK31 and HSP30 on chromosome III of Saccharomyces cerevisiae, is required for growth at 37 degrees C. In this communication, we characterize the ORF and show that disruption of HTL1, besides preventing growth at 37 degrees C, causes genetic and/or epigenetic instability at 26 degrees C: ploidy increases in about 10% of cells grown from individual disruptants and a fraction of disruptant clones are predestined to a rapid and progressive loss of fertility during growth at 26 degrees C.
