Project description:Histones modulate gene expression by chromatin compaction, regulating numerous processes such as differentiation. However, the mechanisms underlying histone degradation remain elusive. When compared with their differentiated counterparts, immortal human embryonic stem cells (hESCs) have a unique chromatin architecture and low levels of trimethylated histone H3 at lysine 9 (H3K9me3), a heterochromatin-associated modification. Here we assess a link between the intrinsic epigenetic landscape and ubiquitin-proteasome system of hESCs. We find that hESCs exhibit high expression of UBE2K, a ubiquitin-conjugating enzyme. Loss of UBE2K increases the levels of H3K9 trimethyltransferase SETDB1, resulting in H3K9 trimethylation and repression of neurogenic genes during differentiation. Concomitantly, loss of UBE2K impairs the ability of hESCs to differentiate into neural progenitors with neurogenic properties. Besides H3K9 trimethylation, we find that UBE2K binds histone H3 to induce its polyubiquitination and degradation by the proteasome. Notably, ubc-20, the worm orthologue of UBE2K, also regulates both histone H3 levels and H3K9 trimethylation in C. elegans germline. Thus, our results indicate that UBE2K crosses evolutionary boundaries to promote histone H3 degradation and reduce H3K9me3 repressive marks in immortal cells.
Project description:To elucidate the Nodal transcriptional network that governs endoderm formation, we used ChIP-Seq to identify genomic targets for SMAD2/3, SMAD3, SMAD4, FOXH1 and the active and repressive chromatin marks, H3K4me3 and H3K27me3, in human embryonic stem cells (hESCs) and derived endoderm. We demonstrate that while SMAD2/3, SMAD4 and FOXH1 target binding is highly dynamic, there is an optimal signature for driving endoderm commitment. Initially, this signature is marked by both H3K4me3 and H3K27me3 as a very broad bivalent domain in hESCs. Within the first 24 hours, at a few select promoters, SMAD2/3 accumulation coincides with H3K27me3 depletion so that these loci become selectively monovalent marked only by H3K4me3. The correlation between SMAD2/3 binding, monovalent formation and transcriptional activation suggests a mechanism by which SMAD proteins coordinate with chromatin at critical promoters to drive endoderm specification. Examination of 2 different histone modifications and 4 different transcription factor associations in 2 cell types. For transcription factor analysis, three biological replicate ChIPs were pooled from each antibody, as well as input controls, for both hESCs and derived endoderm. For histone modifications, two biological replicates for H3K4me3 and three for H3K27me3 were used.
Project description:O-GlcNAcylation performs a critical role in regulating stress response program and cellular homeostasis. However, systematic studies of O-GlcNAc regulated genotoxic stress-responsive transcriptional reprograming have been limited. The GalNAz metabolic labeled global chromatin-associated proteins were isolated from the cross-linked MCF-7 and MCF-7/ADR cells nucleus, and then modified by downstream click-chemistry. The de-crosslinked O-GlcNAz chromatin-bound proteins were enriched for label-free quantitative proteomics by LC-MS/MS.
Project description:To determine the role of autophagy in the maintenance of genome stability and nucleic acid metabolism, the chromatin-bound proteins in autophagy-deficient ATG7-/- HEK293 cells were compared with autophagy-proficient ATG7+/+ HEK293 cells by Data-independent acquisition mass spectrometry (DIA-MS).
Project description:We developed Chromatin Interaction Analysis by Paired-End Tag sequencing (ChIA-PET) for de novo detection of global chromatin interactions, and comprehensively mapped the chromatin interaction network bound by estrogen receptor α (ERα) in the human genome. We performed 454 and Illumina sequencing analyses. Keywords: Epigenetics Using 454, we examined 3 libraries: IHM001 (Estrogen Receptor ChIA-PET), IHM043 (Estrogen Receptor ChIP-PET) and IHM062 (IgG ChIA-PET) Using Illumina, we examined 4 libraries: IHM001 (Estrogen Receptor ChIA-PET replicate 1, Paired End Sequencing), IHH015 (Estrogen Receptor ChIA-PET replicate 2, Paired End Sequencing), H3K4me3 ChIP-Seq and RNA polymerase II ChIP-Seq
Project description:RB’s interaction with chromatin is key to understanding its molecular functions. Using a novel ChIP-sequencing protocol, we identify the precise chromatin loci bound by various forms of human RB. RB targets three fundamentally different types of loci (promoters, enhancers, CTCF-sites), that are largely distinguishable by the mutually exclusive presence of E2F1, c-JUN and CTCF. E2F/DP facilitates RB association with promoters, whereas AP-1 recruits RB to enhancers. RB’s association with promoters and enhancers fluctuates: G1-arrest enriched RB at promoters, while S-phase progression redistributed RB towards enhancers. RB binding to RB/CTCF sites was unaltered by cell cycle progression. RB-bound promoters include the classic E2F targets and are similar between cell types. However, RB-bound enhancers are associated with different gene categories, including, notably, MAPK signaling, and they vary between cell types. We propose that RB has a well-preserved role controlling E2F in G1, and cell type-specific effects at enhancers when cells enter S-phase.
Project description:Purpose: To investigate the transcriptomes of H9 human embryonic stem cells (hESCs)- and peripheral blood mononuclear cells (PBMC) originated induced pluripotent stem cells (iPSCs)-derived early stage lentoid bodies at day 24 through RNA-Seq based whole transcriptome sequencing. Methods: The PBMC obtained from a healthy donor were subjected to generate iPSCs using Sendai-virus delivery system Cytotune 2.0 whereas the H9 hESCs were obtained commercially. Both hESCs and iPSCs were differentiated into lentoid bodies using “fried egg” method with feeder-free conditions as described previously. The differentiating lentoid bodies were examined for the expression of lens-specific and pluripotency markers at days 0, 6, 10, 15 and 24 by quantitative real-time PCR (qRT-PCR). Briefly, four biological replicates for each hESCs- and iPSC-derived lentoid bodies at day 24 were used for the RNA-Seq library preparation followed by sequencing on a single lane of HiSeq 2500. The raw reads were processed and analyzed using Lasergene Genomics Suite and the expression profiles were examined for differential expression using Spotfire DecisionSite with Functional Genomics. Results: The differentiating lentoid bodies at day 24 revealed transparent lens like morphological features with an increased expression of lens-specific markers including CRYGC. A total of 193.41, and 170.00 million reads were obtained for hESCs- and iPSCs-derived lentoid bodies, respectively. Of these, >96% reads aligned to the human reference genome resulting in >200x sequence coverage for both hESCs- and iPSCs-derived lentoid bodies. Additional analysis identified expression (≥ 0.659 RPKM) of 13,991 and 14,018 genes in hESCs- and iPSCs-derived lentoid bodies, respectively, representing ~70% of the total human protein-coding transcriptome expressed in lentoid bodies. Finally, a comparative analysis of both hESCs- and iPSCs-derived lentoid bodies transcriptomes identified >96% similarity at the gene level. Conclusion: The transcriptome analysis revealed an overall similar transcriptional profile in both hESCs- and iPSCs-derived lentoid bodies during differentiation at day 24.