Project description:DAXX, a H3.3 histone chaperone known for its role in heterochromatin maintenance, has been understudied in the context of gene expression regulation. In this study, we generated Daxx knockout myogenic cells and observed a significant loss of myogenic markers expression and impaired differentiation. Transcriptome analysis revealed broad dysregulations in Daxx KO cells, including loss of myogenic identity and a concurrent upregulation of genes involved in DNA replication and telomere maintenance. Chromatin immunoprecipitation followed by sequencing demonstrated a marked reduction in H3.3 deposition, particularly in intronic and intergenic regions. Further analysis indicated that loss of DAXX leads to decreased H3K27ac at myogenic loci and a shift in repressive histone marks, which led to impaired gene expression. Intriguingly, double knockout of Daxx and Hira resulted in distinct transcriptomic alterations, demonstrating that DAXX and HIRA have both overlapping and unique roles in H3.3 incorporation. Our work also suggests the presence of additional histone chaperone complexes in maintaining chromatin integrity in myoblasts. Our findings establish DAXX as a critical regulator of myogenic gene expression and muscle cell identity through a distinct mechanism from that of HIRA and highlighted an unanticipated plasticity in the deposition loci for DAXX and HIRA in myoblasts.
Project description:DAXX, a H3.3 histone chaperone known for its role in heterochromatin maintenance, has been understudied in the context of gene expression regulation. In this study, we generated Daxx knockout myogenic cells and observed a significant loss of myogenic markers expression and impaired differentiation. Transcriptome analysis revealed broad dysregulations in Daxx KO cells, including loss of myogenic identity and a concurrent upregulation of genes involved in DNA replication and telomere maintenance. Chromatin immunoprecipitation followed by sequencing demonstrated a marked reduction in H3.3 deposition, particularly in intronic and intergenic regions. Further analysis indicated that loss of DAXX leads to decreased H3K27ac at myogenic loci and a shift in repressive histone marks, which led to impaired gene expression. Intriguingly, double knockout of Daxx and Hira resulted in distinct transcriptomic alterations, demonstrating that DAXX and HIRA have both overlapping and unique roles in H3.3 incorporation. Our work also suggests the presence of additional histone chaperone complexes in maintaining chromatin integrity in myoblasts. Our findings establish DAXX as a critical regulator of myogenic gene expression and muscle cell identity through a distinct mechanism from that of HIRA and highlighted an unanticipated plasticity in the deposition loci for DAXX and HIRA in myoblasts.
Project description:DAXX, a H3.3 histone chaperone known for its role in heterochromatin maintenance, has been understudied in the context of gene expression regulation. In this study, we generated Daxx knockout myogenic cells and observed a significant loss of myogenic markers expression and impaired differentiation. Transcriptome analysis revealed broad dysregulations in Daxx KO cells, including loss of myogenic identity and a concurrent upregulation of genes involved in DNA replication and telomere maintenance. Chromatin immunoprecipitation followed by sequencing demonstrated a marked reduction in H3.3 deposition, particularly in intronic and intergenic regions. Further analysis indicated that loss of DAXX leads to decreased H3K27ac at myogenic loci and a shift in repressive histone marks, which led to impaired gene expression. Intriguingly, double knockout of Daxx and Hira resulted in distinct transcriptomic alterations, demonstrating that DAXX and HIRA have both overlapping and unique roles in H3.3 incorporation. Our work also suggests the presence of additional histone chaperone complexes in maintaining chromatin integrity in myoblasts. Our findings establish DAXX as a critical regulator of myogenic gene expression and muscle cell identity through a distinct mechanism from that of HIRA and highlighted an unanticipated plasticity in the deposition loci for DAXX and HIRA in myoblasts.
Project description:Our previous studies have implicated CHIP as a co-chaperone/ubiquitin ligase, whose activities yield protection against stress-induced apoptotic events. In this report, we demonstrate a stress-dependent interaction between CHIP (carboxyl terminus of Hsp70-interacting protein) and Daxx, death domain-associated protein. This interaction interferes with the stress-dependent association of HIPK2 with Daxx, blocking phosphorylation of serine 46 in p53 and inhibiting the p53-dependent apoptotic program. Microarray analysis confirmed suppression of the p53-dependent transcriptional portrait in CHIP (+/+) but not in CHIP (-/-) heat shocked MEFs. The interaction between CHIP and Daxx results in ubiquitination of Daxx which is then partitioned to an insoluble compartment of the cell. In vitro ubiquitination of Daxx by CHIP revealed that Ub chain formation utilizes non canonical lysine linkages associated with resistance to proteasomal degradation. CHIP's ubiquitination of Daxx utilizes lysines 630 and 631 and competes with the cell's sumoylation machinery at these residues. These studies implicate CHIP as a stress-dependent regulator of Daxx that counters Daxx's pro-apoptotic influence in the cell. By abrogating p53-dependent apoptotic pathways and by ubiquitination competitive with Daxx sumoylation, CHIP integrates the cell's proteotoxic stress response with cell cycle pathways that influence cell survival. Keywords: p53, apoptosis, cell stress, ubiquitination We utilized a âsample x referenceâ experimental design strategy in which RNA extracted from mouse embryonic fibroblasts was hybridized to the microarray slide in the presence of labeled Universal Mouse Reference RNA (UMRR, Stratagene, LaJolla, CA). A total of 24 RNA samples were used in this analysis. Briefly, five hundred nanograms of total RNA were used for gene expression profiling following reverse transcription and T-7 polymerase-mediated amplification/labeling with Cyanine-5 CTP. Labeled subject cRNA was co-hybridized to Agilent G4112F Whole Mouse Genome 4x44K oligonucleotide arrays with equimolar amounts of Cyanine-3 labeled UHRR. Slides were hybridized, washed, and scanned on an Axon 4000b microarray scanner. The data were processed using Feature Extaction software (Agilent, Santa Clara, CA).
Project description:This study was aimed at understanding the genome-wide binding and regulatory role of the DAXX transcriptional repressor, recently implicated in PCa. ChIP-Seq analysis of genome-wide distribution of DAXX in PC3 cells revealed over 59,000 DAXX binding sites, found at regulatory enhancers and promoters. ChIP-Seq analysis of DNA methyltransferase 1 (DNMT1), which is a key epigenetic partner for DAXX repression, revealed that DNMT1 binding was restricted to a small number of DAXX sites. DNMT1 and DAXX bound close to transcriptional activator motifs. DNMT1 sites were found to be dependent on DAXX for recruitment by analyzing DNMT1 ChIP-Seq following DAXX knockdown (K/D), corroborating previous findings that DAXX recruits DNMT1 to repress its target genes. Massively parallel RNA sequencing (RNA-Seq) was used to compare the transcriptomes of WT and DAXX K/D PC3 cells. Genes induced by DAXX K/D included those involved in autophagy, and DAXX ChIP-Seq peaks were found close to the transcription start sites (TSS) of autophagy genes, implying they are more likely to be regulated by DAXX. To determine DAXX binding sites in the prostate cancer (PCa) genome, the PC3 cell line was used. A stable DAXX shRNA knockdown (K/D) PC3 cell line and a control shRNA counterpart, were compared in a ChIP-Seq study.