DNA methylation of fibroblasts from Cockayne syndrome and UV-sensitivity syndrome patients [450k]
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ABSTRACT: Cockayne syndrome (CS) is a rare genetic disorder caused by mutation of the DNA repair and chromatin remodelling proteins CSA or CSB. Increasing evidences indicate that the progeroid phenotype of CS cannot be solely ascribed to impaired DNA repair, and UV-sensitivity syndrome (UVSS) patients that are also mutated for CSA or CSB do not age prematurely. Epigenetic modifications constitute a hallmark of ageing. We assessed genome-wide DNA methylation (DNAm) at single-nucleotide resolution on fibroblasts derived from CS versus UVSS patients and healthy donors.
Project description:Cockayne syndrome (CS) is a rare genetic disorder caused by mutation of the DNA repair and chromatin remodelling proteins CSA or CSB. Increasing evidences indicate that the progeroid phenotype of CS cannot be solely ascribed to impaired DNA repair, and UV-sensitivity syndrome (UVSS) patients that are also mutated for CSA or CSB do not age prematurely. Epigenetic modifications constitute a hallmark of ageing. We assessed genome-wide DNA methylation (DNAm) at single-nucleotide resolution on fibroblasts derived from CS versus UVSS patients and healthy donors.
Project description:Cockayne syndrome (CS) is an inherited neurodevelopmental disorder with progeroid features. Although the genes responsible for CS have been implicated in a variety of DNA repair- and transcription-related pathways, the nature of the molecular defect in CS remains mysterious. We sought to define this defect by expression analysis of cells lacking functional CSB, a SWI/SNF-like ATPase that is responsible for most CS cases. Keywords: primary disease rescue
Project description:Cockayne syndrome (CS) is an inherited neurodevelopmental disorder with progeroid features. Although the genes responsible for CS have been implicated in a variety of DNA repair- and transcription-related pathways, the nature of the molecular defect in CS remains mysterious. We sought to define this defect by expression analysis of cells lacking functional CSB, a SWI/SNF-like ATPase that is responsible for most CS cases.
Project description:Cockayne Syndrome (CS) is a rare neurodegenerative disease characterized by short stature, cachexia, sun-sensitivity, accelerated aging, and short lifespan. Mutations in two human genes, ERCC8/CSA and ERCC6/CSB, are causative for CS and the protein products of these genes, CSA and CSB, while structurally unrelated, play roles in DNA repair and other aspects of DNA metabolism in human cells. Many clinical and molecular features of CS remain poorly understood, and it has been suggested that CSA and CSB regulate transcription of rDNA genes and ribosome biogenesis. The goal of this study was to investigate the dysregulation of rRNA synthesis in CS. Here, we report that Nucleolin (Ncl), a nucleolar protein that regulates rRNA synthesis and ribosome biogenesis, interacts specifically with CSA and CSB. In addition, CSA induces ubiquitination of Ncl, enhances binding of CSB to Ncl, and CSA and CSB both stimulate binding of Ncl to rDNA and subsequent rRNA synthesis. These findings suggest that CSA and CSB are positive regulators of rRNA synthesis via Ncl regulation. A majority of CS patients carry mutations in CSA and CSB and present with similar clinical features, thus our findings may provide novel insights into disease mechanism and the neuropathological features of CS.
Project description:CSA and CSB proteins are key players in transcription-coupled nucleotide excision repair (TC-NER) pathway that removes UV-induced DNA lesions from the transcribed strands of expressed genes. Additionally, CS proteins play relevant but still elusive roles in other cellular pathways whose alteration may explain neurodegeneration and progeroid features in Cockayne syndrome (CS). Here we identify a CSA-dependent chromatin-associated protein complex that modulates rRNA transcription. Besides RNA polymerase I (RNAP1) and specific ribosomal proteins (RPs), the CSA complex includes ferrochelatase (FECH), a well-known mitochondrial enzyme whose deficiency causes erythropoietic protoporphyria (EPP). Impairment of either CSA or FECH functionality leads to reduced RNAP1 occupancy on rDNA promoter that is associated to reduced transcription when CSA is affected and abnormal ribosomal transcript accumulation after FECH silencing. Accordingly, primary fibroblasts from CS and EPP fibroblasts show opposed amount of total rRNAs. After cell irradiation with UV light, CSA triggers the dissociation of the CSA-FECH-RNAP1-RPs complex from the chromatin while it stabilizes its binding to FECH. Besides disclosing a function for FECH within nucleoli, this study sheds light on the still unknown mechanisms through which CSA modulates rRNA transcription.
Project description:The rare genetic disease Cockayne syndrome (CS) results in mutations in CSA and CSB. Upon UV irradiation, RNA synthesis was arrested: RNA-seq showed 70% of down-regulated genes in common between CSA and CSB deficient cells. ATF3, the product of an immediate early gene was overexpressed and bound to its CRE/ATF site to inhibit its responsive genes. ChIP experiments showed that CSA/CUL4A/DDB1 together with CSB and MDM2, target ATF3. In vivo and in vitro experiments showed that ATF3 was ubiquitilated by a concerted action of CSA and MDM2 ubiquitin-ligases and was further eliminated by the proteasome concomitantly with the recruitment of RNA polymerase II to restart transcription. In CS cells, dysfunctional CSA or CSB were unable to assemble the ubiquitin/proteasome complex, thereby maintaining the ATF3-dependent transcription arrested. Though, in addition to their function in DNA repair, CSA and CSB might thus regulate the timing of DNA binding factors on its specific target site via the ubiquitin/proteasome machinery.
Project description:The rare genetic disease Cockayne syndrome (CS) results in mutations in CSA and CSB. Upon UV irradiation, RNA synthesis was arrested: RNA-seq showed 70% of down-regulated genes in common between CSA and CSB deficient cells. ATF3, the product of an immediate early gene was overexpressed and bound to its CRE/ATF site to inhibit its responsive genes. ChIP experiments showed that CSA/CUL4A/DDB1 together with CSB and MDM2, target ATF3. In vivo and in vitro experiments showed that ATF3 was ubiquitilated by a concerted action of CSA and MDM2 ubiquitin-ligases and was further eliminated by the proteasome concomitantly with the recruitment of RNA polymerase II to restart transcription. In CS cells, dysfunctional CSA or CSB were unable to assemble the ubiquitin/proteasome complex, thereby maintaining the ATF3-dependent transcription arrested. Though, in addition to their function in DNA repair, CSA and CSB might thus regulate the timing of DNA binding factors on its specific target site via the ubiquitin/proteasome machinery.
Project description:Cockayne syndrome (CS) is an accelerated aging disorder characterized by progressive neurodegeneration caused by mutations in the genes encoding the DNA repair proteins CSA or CSB. Csbm/m mice were given a high-fat, caloric-restricted or resveratrol-supplemented diet. The high-fat diet rescued the phenotype of Csbm/m mice at the metabolic, transcriptomic and behavioral levels. Additional analysis suggests that the premature aging seen in CS mice, nematodes and human cells results from aberrant PARP activation due to deficient DNA repair leading to decreased SIRT1 activity and mitochondrial dysfunction. Notably, β-hydroxybutyrate levels are increased by the high-fat diet; and β-hydroxybutyrate, PARP inhibition, or NAD+ supplementation can activate SIRT1 and rescue CS-associated phenotypes. Mechanistically, CSB is able to displace activated PARP1 from damaged DNA to limit its activity. This study connects two emerging longevity metabolites, β-hydroxybutyrate and NAD+, through the deacetylase SIRT1 and suggests possible interventions for CS.
Project description:Cockayne syndrome (CS) is a rare premature aging disease, which in the majority of cases is caused by mutations of the genes encoding the CSA or CSB proteins. CS patients display cachectic dwarfism and severe neurological manifestations and die by 12 years of age on average. The CS proteins are involved in transcription and DNA repair, including a specialized form of DNA repair called transcription-coupled nucleotide excision repair (TC-NER). However, there is also evidence for mitochondrial dysfunction in CS, likely contributing to the severe premature aging phenotype of this disease. Our cross-species transciptomic analysis in CS postmortem brain tissue, CS mouse and C. elegans models showed that mitochondrial dysfunction is indeed a common feature in CS. Interestingly, the restoration of mitochondrial dysfunction through NAD+ supplementation significantly improved lifespan and healthspan in the C. elegans models of CS, highlighting mitochondrial dysfunction as a major driver of the aging features of CS. We proceeded to perform molecular studies on cerebellar samples obtained from CS patients. We found that these patients exhibited molecular signatures of dysfunctional mitochondrial dynamics that can be corrected with NAD+ supplementation in primary cells with depleted CSA or CSB. Our study provides support for the interconnection between two major aging theories, DNA damage and mitochondrial dysfunction. Together these two agents contribute to an accelerated aging program that can be averted by NAD+ supplementation.
Project description:Cockayne syndrome (CS) is a rare premature aging disease, which in the majority of cases is caused by mutations of the genes encoding the CSA or CSB proteins. CS patients display cachectic dwarfism and severe neurological manifestations and die by 12 years of age on average. The CS proteins are involved in transcription and DNA repair, including a specialized form of DNA repair called transcription-coupled nucleotide excision repair (TC-NER). However, there is also evidence for mitochondrial dysfunction in CS, likely contributing to the severe premature aging phenotype of this disease. Our cross-species transciptomic analysis in CS postmortem brain tissue, CS mouse and C. elegans models showed that mitochondrial dysfunction is indeed a common feature in CS. Interestingly, the restoration of mitochondrial dysfunction through NAD+ supplementation significantly improved lifespan and healthspan in the C. elegans models of CS, highlighting mitochondrial dysfunction as a major driver of the aging features of CS. We proceeded to perform molecular studies on cerebellar samples obtained from CS patients. We found that these patients exhibited molecular signatures of dysfunctional mitochondrial dynamics that can be corrected with NAD+ supplementation in primary cells with depleted CSA or CSB. Our study provides support for the interconnection between two major aging theories, DNA damage and mitochondrial dysfunction. Together these two agents contribute to an accelerated aging program that can be averted by NAD+ supplementation.