CSB ablation induced apoptosis is mediated by Increased Endoplasmic Reticulum Stress Response: a gene expression study
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ABSTRACT: The DNA repair protein, Cockayne syndrome group B (CSB), has been recently identified as a promising anticancer target. Suppression, by antisense technology, of this protein causes devastating effects on tumor cells viability, through a massive induction of apoptosis, while being non-toxic to non-transformed cells. To gain insights into the mechanisms underlying the pro-apoptotic effects observed after CSB ablation, global gene expression patterns were determined, to identify genes that were significantly differentially regulated as a function of CSB expression. The one-color Agilent microarray platform was used. The study revealed that response to endoplasmic reticulum stress and response to unfolded proteins were ranked top amongst the cellular processes affected by CSB suppression.
Project description:Cockayne syndrome is a segmental progeria most often caused by mutations in the CSB gene encoding a SWI/SNF-like ATPase required for transcription-coupled DNA repair (TCR). Over 43 Mya before marmosets diverged from humans, a piggyBac3 (PGBD3) transposable element integrated into intron 5 of the CSB gene. As a result, primate CSB genes now generate both CSB protein and a conserved CSB-PGBD3 fusion protein in which the first 5 exons of CSB are alternatively spliced to the PGBD3 transposase. We show by microarray analysis that expression of the fusion protein alone in CSB-null UV-sensitive syndrome cells (UVSS1KO) cells induces an interferon-like response that resembles both the innate antiviral response and the prolonged interferon response normally maintained by unphosphorylated STAT1 (U-STAT1); moreover, as might be expected based on conservation of the fusion protein, this potentially cytotoxic interferon-like response is largely reversed by coexpression of functional CSB protein. Interestingly, expression of CSB and the CSB-PGBD3 fusion protein together, but neither alone, upregulates the insulin growth factor binding protein IGFBP5 and downregulates IGFBP7, suggesting that the fusion protein may also confer a metabolic advantage, perhaps in the presence of DNA damage. Finally, we show that the fusion protein binds in vitro to members of a dispersed family of 900 internally deleted piggyBac elements known as MER85s, providing a potential mechanism by which the fusion protein could exert widespread effects on gene expression. Our data suggest that the CSB-PGBD3 fusion protein is important in both health and disease, and could play a role in Cockayne syndrome. 12 samples total; 4 gene expression conditions in triplicate; 1 condition is a tag-only negative control
Project description:Cockayne syndrome is a segmental progeria most often caused by mutations in the CSB gene encoding a SWI/SNF-like ATPase required for transcription-coupled DNA repair (TCR). Over 43 Mya before marmosets diverged from humans, a piggyBac3 (PGBD3) transposable element integrated into intron 5 of the CSB gene. As a result, primate CSB genes now generate both CSB protein and a conserved CSB-PGBD3 fusion protein in which the first 5 exons of CSB are alternatively spliced to the PGBD3 transposase. We show by microarray analysis that expression of the fusion protein alone in CSB-null UV-sensitive syndrome cells (UVSS1KO) cells induces an interferon-like response that resembles both the innate antiviral response and the prolonged interferon response normally maintained by unphosphorylated STAT1 (U-STAT1); moreover, as might be expected based on conservation of the fusion protein, this potentially cytotoxic interferon-like response is largely reversed by coexpression of functional CSB protein. Interestingly, expression of CSB and the CSB-PGBD3 fusion protein together, but neither alone, upregulates the insulin growth factor binding protein IGFBP5 and downregulates IGFBP7, suggesting that the fusion protein may also confer a metabolic advantage, perhaps in the presence of DNA damage. Finally, we show that the fusion protein binds in vitro to members of a dispersed family of 900 internally deleted piggyBac elements known as MER85s, providing a potential mechanism by which the fusion protein could exert widespread effects on gene expression. Our data suggest that the CSB-PGBD3 fusion protein is important in both health and disease, and could play a role in Cockayne syndrome.
Project description:The CSB-PGBD3 fusion protein arose over 43 million years ago when a 2.5 kb piggyBac 3 (PGBD3) transposon inserted into intron 5 of the Cockayne syndrome Group B (CSB) gene in the common ancestor of all higher primates. The CSB-PGBD3 fusion protein binds internally-deleted PGBD3 elements called MER85s in vitro, and induces a strong interferon-like innate antiviral immune response when expressed in CSB-null UVSS1KO cells. To explore the connection between DNA binding and gene expression changes induced by CSB-PGBD3, we investigated the genome-wide DNA binding profile of the fusion protein. 1 ChIP sample and 1 unenriched input control from the same crosslinked chromatin pool
Project description:The CSB-PGBD3 fusion protein arose over 43 million years ago when a 2.5 kb piggyBac 3 (PGBD3) transposon inserted into intron 5 of the Cockayne syndrome Group B (CSB) gene in the common ancestor of all higher primates. The CSB-PGBD3 fusion protein binds internally-deleted PGBD3 elements called MER85s in vitro, and induces a strong interferon-like innate antiviral immune response when expressed in CSB-null UVSS1KO cells. To explore the connection between DNA binding and gene expression changes induced by CSB-PGBD3, we investigated the genome-wide DNA binding profile of the fusion protein.
Project description:We investigated whether transcription-coupled repair deficient mice (Cockayne syndrome B knockout mice (Csb-/-)), known to be sensitive to oxidative stressors, have a different response to ozone than its repair-proficient control, Csb heterozygote (Csb+/-) mice.
Project description:Cockayne syndrome (CS) is a rare genetic neurodevelopmental disorder, characterized by a deficiency in the transcription-coupled nucleotide excision repair pathway. Mutation of Cockayne syndrome B (CSB) affects basal transcription which is considered a major cause of CS neurological dysfunction. Here, we generated a rat model by mimicking a nonsense mutation in the CSB(ERCC6) gene of CS-B patients. CSB-deficient rats exhibit the well-known CS repair characteristics: inability to resume RNA synthesis from stalled RNA polymerase II (RNAP II) and persistent gamma H2AX overexpression after UV damage. In contrast to that of the Csb-/- mouse models, the cerebella of the CSB-deficient rats are more profoundly affected. Both the molecular and the granular layers of the cerebellum cortex showed significant atrophy. The white matter of the cerebellum demonstrated high GFAP staining indicative of reactive astrogliosis. RNA-seq analysis of CSB-deficient rat cerebella revealed that even in the absence of UV damage, CSB affects the expression of hundreds of genes, many of which are neuronal genes, suggesting that transcription dysregulation could contribute to the neurological features in CSB rat models.
Project description:The DNA repair protein Cockayne syndrome group B (CSB) has been recently identified as a promising anticancer target. Suppression, by antisense technology, of this protein causes devastating effects on tumor cells viability, through a massive induction of apoptosis, while being non-toxic to non-transformed cells. To gain insights into the mechanisms underlying the pro-apoptotic effects observed after CSB ablation, global gene expression patterns were determined, to identify genes that were significantly differentially regulated as a function of CSB expression. Our findings revealed that response to endoplasmic reticulum stress and response to unfolded proteins were ranked top amongst the cellular processes affected by CSB suppression. The major components of the endoplasmic reticulum stress-mediated apoptosis pathway, including pro-apoptotic factors downstream of the ATF3-CHOP cascade, were dramatically up-regulated. Altogether our findings add new pieces to the understanding of CSB mechanisms of action and to the molecular basis of CS syndrome.
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:Mutations in the CSA and CSB genes are causative of Cockayne syndrome neurological disorder. Since the identification of the indispensable functions of these two proteins in transcription-coupled repair and restoring RNA synthesis following DNA damage, the paradoxical milder clinical spectrum in CS-A patients has been puzzling. In this study we compared the effect of a CSA and a CSB defect at the levels of the cell and the intact organism. We showed that CSA-deficient zebrafish embryos exhibited modest hypersensitive to UV damage than CSB depletion. We found that loss of CSA can effectively release aggregation of mutant crystallin proteins in vitro. We described the distinct effect of CSA and CSB on neuritogenesis and elucidated the differentiated gene expression pathways regulated by these two proteins. Our data demonstrate convergent and divergent roles for CSA and CSB in DNA repair and transcription regulation and provide explanations for the reported differences between CS-A and CS-B patients.
Project description:Cockayne syndrome is an inherited premature aging syndrome associated with developmental and neurological disorders. Mutations in the genomic locus encoding CSB are associated with 80% Cockayne syndrome cases. CSB is invovled in relieving UV-induced and oxidative stree. To gain more insights into the fucntion of CSB under these stress, we use ChIP-seq to determine the genomic localization of CSB 1 hour after UV irradiation and menadione treatment. Genomic localization of CSB and remodeling deficient CSBâN1