Project description:We executed CUT&RUN-seq for SWI/SNF components ARID1A, BRD9, SMARCA4, SMARCB1, SMARCE1, as well as ESRRB, SOX2, and EZH2 in asynchronous and mitotic cells and reported that, in asynchronous cells, ARID1A localized primarily at enhancer regions and EZH2 preferentially deposited at bivalent promoters and silent enhancer domains. The remaining factors were enriched at both TSS/promoters and to varying degrees at active enhancers. Unexpectedly, in mitosis, the chromatin regulatory factors almost all tethered at proximal gene regions with very little binding at enhancers. While the SWI/SNF subunits were bound principally at promoters, EZH2, the catalytic subunit of Polycomb Repressive Complex 2 was bound at both promoters and silent enhancers in mitotic cells. Moreover, we reported that upon the degradation of SMARCE1 in mitosis, the occupancy of SOX2, ESRRB, and EZH2 on mitotic chromatin was disrupted.
Project description:We report genome wide mapping of the histone variant H2A.Z during G0/G1 and mitosis in T24 bladder cancer cells. The results show that the broad enrichment pattern of H2A.Z near transcription start sites of active genes is maintained during mitosis. Furthermore, using H2A.Z localization to visualize nucleosome positioning near the start site, we see that the +1 nucleosome of active genes shifts upstream to occupy the transcription start sites during mitosis and the nucleosome depleted region is shortened. H2A.Z is also maintained on the -2 nucleosome which also shifts towrds the transcription start site during mitosis, further contributing to the shorteneing of the nucleosome depleted region. Examination of H2A.Z duing G0/G1 and mitosis in bladder cancer cells
Project description:SMARCE1 binding on mitotic chromatin is required for the timely reinitiation of expression of SMARCE1-bookmarked genes and maintaining identity memory in cell division.
Project description:Here we compare the distribution of insulator proteins during interphase and mitosis. We performed ChIP-seq analysis on purified populations of interphase and mitotic Kc cells, using antibodies against CP190, dCTCF, BEAF, and Su(Hw). Examination of 4 different insulator proteins during interphase and mitosis
Project description:SMARCE1 binding on mitotic chromatin is required for the timely reinitiation of expression of SMARCE1-bookmarked genes and maintaining identity memory in cell division.
Project description:Mitosis entails global alterations to chromosome structure and nuclear architecture, concomitant with transient silencing of transcription. How cells transmit transcriptional states through mitosis remains incompletely understood. While many nuclear factors dissociate from mitotic chromosomes, the observation that certain nuclear factors and chromatin features remain associated with individual loci during mitosis originated the hypothesis that they could provide transcriptional memory through mitosis. To obtain the first genome-wide view of the dynamics of chromatin structure during mitosis, we compared the DNase sensitivity of interphase and mitotic chromatin at two stages of cellular maturation in a rapidly dividingmurine erythroblastmodel. Despite global chromosome condensation visible during mitosis at the microscopic level, the chromatin accessibility landscape is largely unaltered. However, mitotic chromatin accessibility is locally dynamic, with individual loci maintaining none, some, or all of their interphase accessibility. Mitotic reduction in accessibility occurs primarily within narrow, highly hypersensitive sites that frequently coincide with transcription factor binding sites, whereas broader domains of moderate accessibility tend to be more stable. In mitosis, proximal promoters generally maintain their accessibility, whereas distal regulatory elements preferentially lose accessibility. Promoters with the highest degree of accessibility preservation in mitosis tend to also be accessible across many murine tissues in interphase. Transcription factor GATA1 exerts site-specific changes in interphase accessibility that are most pronounced at distal regulatory elements, but does not visibly influence mitotic accessibility. We conclude that features of open chromatin are remarkably stable through mitosis and are modulated at the level of individual genes and regulatory elements. Dnase-Seq data is integrated with Chip-seq [GSE36589, GSE30142] and RNA-seq to examine epigentic changes in mitosis. We performed DNase-seq on two cell lines, G1E and G1E-ER4, both on an asynchronus population, and on a sample of cells in mitosis; each of the 4 experiments in triplicate.
Project description:For cells to initiate and sustain a differentiated state, it is necessary that a “memory” of this state is transmitted through mitosis to the daughter cells. Mammalian SWItch/ Sucrose Non- Fermentable (SWI/SNF) complexes, also called Brg1/ Brg- associated factors (BAF), control cell identity by modulating chromatin architecture to regulate gene expression, but whether they participate in cell fate memory is unclear. Here, we provide evidence that subunits of SWI/SNF act as mitotic bookmarks to safeguard cell identity during cell division. The SWI/SNF core subunits SMARCE1 and SMARCB1 are displaced from enhancers but bound on promoters during mitosis and we show that this binding is required for appropriate reactivation of bound genes after mitotic exit. Ablation of SMARCE1 during a single mitosis in mouse embryonic stem cells is sufficient to disrupt gene expression, impair the occupancy of several established bookmarks at a subset of their targets, and cause aberrant neural differentiation. Thus, SWI/SNF subunit SMARCE1 plays a mitotic bookmarking role and is essential for heritable epigenetic fidelity during transcriptional reprogramming.
Project description:Entry into and exit from mitosis is driven by precisely-timed changes in protein abundance, and involves transcriptional regulation and protein degradation. However, the role of translational regulation in modulating cellular protein content during mitosis remains poorly understood. Here, using ribosome profiling, we show that translational, rather than transcriptional regulation is the dominant mechanism for modulating protein synthesis at mitotic entry. The vast majority of regulated mRNAs are translationally repressed, which contrasts previous findings of selective mRNA translational activation at mitotic entry. One of the most pronounced translationally repressed genes in mitosis is Emi1, an inhibitor of the anaphase promoting complex (APC), which is degraded during mitosis. We show that Emi1 degradation is insufficient for full APC activation and that simultaneous translational repression is required. These results provide a genome-wide view of protein translation during mitosis and suggest that translational repression may be used to ensure complete protein inactivation Ribosome profiling and mRNA-seq from 3 time points in the cell cycle
Project description:Epigenetic regulation of gene expression, including by Polycomb Group (PcG) proteins, may depend on heritable chromatin states but how these states can be propagated through mitosis is unclear. Using immunofluorescence and biochemical fractionation, we find PcG proteins associated with mitotic chromosomes in Drosophila S2 cells. Genome-wide sequencing of chromatin immunoprecipitations (ChIP-SEQ) from mitotic cells indicates that Posterior Sex Combs (PSC) and Polyhomeotic (PH) are not present at well-characterized PcG targets including Hox genes in mitosis, but do remain at 11% of their interphase sites. 26% of interphase PSC sites overlap with recently described chromatin domain borders (Sexton et al., 2012), which are genomic regions characterized by low levels of long range contacts. PSC and PH are preferentially retained at these sites in mitosis, including borders flanking both Hox gene clusters. We hypothesize that disruption of long range chromatin contacts in mitosis contributes to PcG protein release from most sites, while persistent binding at sites with minimal long range contacts may nucleate re-establishment of PcG binding and chromosome organization after mitosis. Drosophila S2 cells were colchicine-treated and stained with anti-H3S10p antibody and FACS sorted to give mitotic samples. In parallel asynchronous Drosophila S2 cell cultures were stained for anti-H3 antibody and FACS sorted to give control samples. Chromatin from each of these sorted populations was immunoprecipitated using biotinylated antibodies against PSC. Two replicates of these samples are included. A stable Drosophila S2 cell line expressing biotin-tagged PH was also FACS sorted as above to give mitotic and control samples, and streptavidin-coated beads were used to pulldown biotinlyated PH. Inputs are included for each sample.
Project description:Entry into and exit from mitosis is driven by precisely-timed changes in protein abundance, and involves transcriptional regulation and protein degradation. However, the role of translational regulation in modulating cellular protein content during mitosis remains poorly understood. Here, using ribosome profiling, we show that translational, rather than transcriptional regulation is the dominant mechanism for modulating protein synthesis at mitotic entry. The vast majority of regulated mRNAs are translationally repressed, which contrasts previous findings of selective mRNA translational activation at mitotic entry. One of the most pronounced translationally repressed genes in mitosis is Emi1, an inhibitor of the anaphase promoting complex (APC), which is degraded during mitosis. We show that Emi1 degradation is insufficient for full APC activation and that simultaneous translational repression is required. These results provide a genome-wide view of protein translation during mitosis and suggest that translational repression may be used to ensure complete protein inactivation