Project description:Pseudoautosomal regions (PAR1 and PAR2) in eutherians retain homologous regions between the X and Y chromosomes that play a critical role in the obligatory X-Y crossover during male meiosis. Genes that reside in the PAR1 are exceptional in that they are rich in repetitive sequences and undergo a very high rate of recombination. Remarkably, murine PAR1 homologs have translocated to various autosomes, reflecting the complex recombination history during the evolution of the mammalian X chromosome. We now report that the SNF2-type chromatin remodeling protein ATRX controls the expression of eutherians ancestral PAR1 genes that have translocated to autosomes in the mouse. In addition, we have identified two potentially novel mouse PAR1 orthologs. We propose that the ancestral PAR1 genes share a common epigenetic environment that allows ATRX to control their expression. At E13.5, n = 3 biological replicates of littermate-matched wt/ko pairs. RNA from 2 forebrains were pooled to generate enough RNA for each sample. At P0.5, n = 4 biological replicates of littermate-matched wt/ko pairs (for pair #2 there is one wt and 2 Atrx-null samples (2A & 2B) and we count this as 2 pairs).
Project description:Pseudoautosomal regions (PAR1 and PAR2) in eutherians retain homologous regions between the X and Y chromosomes that play a critical role in the obligatory X-Y crossover during male meiosis. Genes that reside in the PAR1 are exceptional in that they are rich in repetitive sequences and undergo a very high rate of recombination. Remarkably, murine PAR1 homologs have translocated to various autosomes, reflecting the complex recombination history during the evolution of the mammalian X chromosome. We now report that the SNF2-type chromatin remodeling protein ATRX controls the expression of eutherians ancestral PAR1 genes that have translocated to autosomes in the mouse. In addition, we have identified two potentially novel mouse PAR1 orthologs. We propose that the ancestral PAR1 genes share a common epigenetic environment that allows ATRX to control their expression.
Project description:ATRX is a severe X-linked disorder characterized by mental retardation, facial dysmorphism, urogenital abnormalities and alpha-thalassemia. The disease is caused by mutations in ATRX gene, which encodes a protein belonging to the SWI/SNF DNA helicase family, a group of proteins involved in the regulation of gene transcription at the chromatin level. In order to identify specific genes involved in the pathogenesis of the disease, we compared, by cDNA microarray, the expression levels of approximately 8500 transcripts between ATRX and normal males of comparable age. The analysis has been performed on pooled RNA extracted by Peripheral blood mononuclear cell pellet of three male ATRX patients in comparison to that obtained from a pool of 42 normal males (age 7.6+ 2.4).
Project description:The X-linked alpha thalassaemia intellectual disability syndrome (ATRX) protein is a member of the SWI/SNF family of chromatin remodelling factors which acts as an ATP dependent molecular motor. Germline mutations in ATRX give rise to a severe form of syndromal intellectual disability (ATR-X syndrome). To date, only a small number of genes have been identified that are affected by pathogenic ATRX mutations in human. We performed microarray experiments on LCLs from normal individuals and patients with diverse pathogenic ATRX mutations, to identify more genes regulated by ATRX.
Project description:The histone variant macroH2A generally associates with transcriptionally inert chromatin, however the factors that regulate its chromatin incorporation remain elusive. Here, we identify the SWI/SNF helicase, ATRX, as a novel macroH2A interacting protein. Unlike its role in assisting H3.3 chromatin deposition, ATRX acts as a negative regulator of macroH2A’s chromatin association. In human erythroleukemic cells deficient for ATRX, ChIP-sequencing studies reveal that macroH2A accumulates at the HBA gene cluster on the subtelomere of chromosome 16, coinciding with the loss of α globin expression. Collectively, our results implicate deregulation of macroH2A’s distribution as a contributing factor to the α thalassemia phenotype of ATRX syndrome. Mononucleosomes from K562 cells bearing integrated lentiviral shRNA constructs targeting either luciferase (shluc) or ATRX (sh92) were isolated and ChIP'd with mH2A1 antibody. DNA from shluc Input and the two mH2A1 ChIPs were isolated and sequenced on Illumina's Hiseq.
Project description:ATRX is a severe X-linked disorder characterized by mental retardation, facial dysmorphism, urogenital abnormalities and alpha-thalassemia. The disease is caused by mutations in ATRX gene, which encodes a protein belonging to the SWI/SNF DNA helicase family, a group of proteins involved in the regulation of gene transcription at the chromatin level. In order to identify specific genes involved in the pathogenesis of the disease, we compared, by cDNA microarray, the expression levels of approximately 8500 transcripts between ATRX and normal males of comparable age.
Project description:ATRX is an X-linked gene of the SWI/SNF family whose role in vivo is currently unknown. Mutations in ATRX cause syndromal mental retardation. ATRX binds to tandem repeat (TR) sequences both in heterochromatin (e.g. telomeres) and euchromatin. Genes associated with these TRs can be dysregulated when ATRX is mutated and the degree to which their expression changes is determined by the size of the TR, producing skewed allelic expression. This explains the nature of the affected genes, the variable phenotypes seen with identical ATRX mutations and also illustrates a new mechanism underlying variable penetrance. Many of the TRs in ATRX targets are G-rich and predicted to form non-B DNA structures (including G quadruplex) in vivo. We have shown that ATRX binds G quadruplex structures in vitro suggesting a mechanism by which ATRX may play a role in various nuclear processes and how this is perturbed when ATRX is mutated. 4 Human Erythroblast, 1 HEP3B and 1 Fibroblast ChIP-ChIP Sample For ChIP-Seq: one human erythroblasts, one mouse ES, one human erythroblast reference Sample, and one mouse ES input reference Sample.
Project description:SWItch/Sucrose Non-Fermenting (SWI/SNF) complexes are a family of chromatin remodellers that are conserved across eukaryotes. Mutations in subunits of SWI/SNF cause a multitude of different developmental disorders in humans, most of which have no current treatment options. Here we identify an alanine to valine causing mutation in the SWI/SNF subunit snfc-5 (SMARCB1 in humans) that prevents embryonic lethality in C. elegans nematodes harbouring a loss-of-function mutation in the SWI/SNF subunit swsn-1 (SMARCC1/2 in humans). Furthermore, we found that the combination of this specific mutation in snfc-5 and a loss-of-function mutation in either of the E3 ubiquitin ligases ubr-5 (UBR5 in humans) or hecd-1 (HECTD1 in humans) can restore development to adulthood in swsn-1 loss-of-function mutants that otherwise die as embryos. Using these mutant models, we established a set of 335 genes that are dysregulated in SWI/SNF mutants that arrest their development embryonically but exhibit near wild-type levels of expression in the presence of suppressor mutations that prevent embryonic lethality, suggesting that SWI/SNF promotes development by regulating this specific subset of genes. In addition, we show that SWI/SNF protein levels are reduced in swsn-1; snfc-5 double mutants and partly restored to wild-type levels in swsn-1; snfc-5; ubr-5 triple mutants, consistent with a model in which UBR-5 regulates SWI/SNF levels by tagging the complex for proteasomal degradation. Our findings establish a link between two E3 ubiquitin ligases and SWI/SNF function and suggest that UBR5 and HECTD1 might be viable therapeutic targets for the many developmental disorders caused by missense mutations in SWI/SNF subunits.
Project description:Here we performed transcriptional profiling of the prostate cancer cell lines LNCaP and 22Rv1 comparing non-targeting siRNA treatment versus siRNAs targeting SWI/SNF complex proteins (SMARCA2, SMARCA4, and SMARCB1). Goal was to determine the effect of SWI/SNF knockdown on gene expression in prostate cancer. Two-condition experiment: non-targeting siRNA versus SWI/SNF-siRNA treated cells. Three SWI/SNF proteins were targeted: SMARCA2, SMARCA4, and SMARB1. Biological replicates: 1 control replicate, 2 treatment replicates per SWI/SNF protein. Technical replicates: 1 replicate per SWI/SNF protein. Cell lines: 22Rv1 and LNCaP.
Project description:The SWI/SNF ATP-dependent chromatin remodeler is a master regulator of the epigenome; controlling pluripotency, cell fate determination and differentiation. There is a sparsity of information on the autoregulation of SWI/SNF, the domains involved and their mode of action. We find a DNA or RNA binding module conserved from yeast to humans located in the C-terminus of the catalytic subunit of SWI/SNF called the AT-hook that positively regulates the chromatin remodeling activity of yeast and mouse SWI/SNF. The AT-hook in yeast SWI/SNF interacts with the SnAC and ATPase domains, which after binding to nucleosome switches to contacting the N-terminus of histone H3. Deletion of the AT-hooks in yeast SWI/SNF and mouse esBAF complexes reduces the remodeling activity of SWI/SNF without affecting complex integrity or its recruitment to nucleosomes. In addition, deletion of the AT-hook impairs the ATPase and nucleosome mobilizing activities of yeast SWI/SNF without disrupting the interactions of the ATPase domain with nucleosomal DNA. The AT-hook is also important in vivo for SWI/SNF-dependent response to amino acid starvation in yeast and for cell lineage priming in mouse embryonic stem cells. In summary, the AT-hook is shown to be an evolutionarily conserved autoregulatory domain of SWI/SNF that positively regulates SWI/SNF both in vitro and in vivo.