Project description:DNA replicates once per cell cycle. Interfering with the regulation of DNA replication initiation generates genome instability through over-replication and has been linked to early stages of cancer development. Here, we engineered genetic systems in budding yeast to induce unscheduled replication in the G1-phase of the cell cycle. Unscheduled G1 replication initiated at canonical S-phase origins across the genome. We quantified differences in replisomes in G1- and S-phase and identified firing factors, polymerase α, and histone supply as factors that limit replication outside S-phase. G1 replication per se did not trigger cellular checkpoints. Subsequent replication during S-phase, however, resulted in over-replication and led to chromosome breaks via head-to-tail replication fork collisions that are marked by chromosome-wide, strand-biased occurrence of RPA-bound single-stranded DNA. Low-level, sporadic induction of G1 replication induced an identical response, indicating findings from synthetic systems are applicable to naturally occurring scenarios of unscheduled replication initiation by G1/S deregulation.
Project description:Identity-specific interphase chromosome conformation must be re-established each time a cell divides. To understand how interphase folding is inherited, we developed an experimental approach that segregates chromosome-intrinsic factors from those inherited through the cytoplasm during the establishment of G1 nuclear architecture. Endogenous RanGAP1 or Nup93 proteins were degraded in pro-metaphase arrested DLD-1 cells to prevent the establishment of nucleo-cytoplasmic transport during mitotic exit and isolate the decondensing mitotic chromatin of G1 daughter cells from the cytoplasm. Using this approach, we uncovered a transient folding intermediate entirely driven by chromosome-intrinsic factors. In addition to conventional compartmental segregation, this chromosome-intrinsic folding program leads to prominent genome-scale microcompartmentalization of mitotically bookmarked and cell type-specific cis-regulatory elements. The microcompartment conformation is formed during telophase and subsequently modulated by a second folding program driven by factors inherited through the cytoplasm in G1. The nuclear import-dependent folding program includes cohesin and factors involved in transcription and RNA processing. The combined and inter-dependent action of chromosome-intrinsic and cytoplasmic inherited folding programs determines the interphase chromatin conformation as cells exit mitosis.
Project description:Identity-specific interphase chromosome conformation must be re-established each time a cell divides. To understand how interphase folding is inherited, we developed an experimental approach that physically segregates mediators of G1 folding that are intrinsic to mitotic chromosomes from cytoplasmic factors. Proteins essential for nuclear transport, RanGAP1 and Nup93, were degraded in pro-metaphase arrested DLD-1 cells to prevent the establishment of nucleo-cytoplasmic transport during mitotic exit and isolate the decondensing mitotic chromatin of G1 daughter cells from the cytoplasm. Using this approach, we discover a transient folding intermediate entirely driven by chromosome-intrinsic factors. In addition to conventional compartmental segregation, this chromosome-intrinsic folding program leads to prominent genome-scale microcompartmentalization of mitotically bookmarked and cell type-specific cis-regulatory elements. The microcompartment conformation is formed during telophase and subsequently modulated by a second folding program driven by factors inherited through the cytoplasm in G1. This nuclear import-dependent folding program includes cohesin and factors involved in transcription and RNA processing. The combined and inter-dependent action of chromosome-intrinsic and cytoplasmic inherited folding programs determines the interphase chromatin conformation as cells exit mitosis. In our proteomics dataset we identify factors requiring nuclear import to access the genome at the end of mitosis.
Project description:Identity-specific interphase chromosome conformation must be re-established each time a cell divides. To understand how interphase folding is inherited, we developed an experimental approach that physically segregates mediators of G1 folding that are intrinsic to mitotic chromosomes from cytoplasmic factors. Proteins essential for nuclear transport, RanGAP1 and Nup93, were degraded in pro-metaphase arrested DLD-1 cells to prevent the establishment of nucleo-cytoplasmic transport during mitotic exit and isolate the decondensing mitotic chromatin of G1 daughter cells from the cytoplasm. Using this approach, we discover a transient folding intermediate entirely driven by chromosome-intrinsic factors. In addition to conventional compartmental segregation, the chromosome-intrinsic folding program leads to prominent genome-scale microcompartmentalization of mitotically bookmarked and cell type-specific cis-regulatory elements. The microcompartment conformation is formed during telophase and subsequently modulated by a second folding program driven by factors inherited through the cytoplasm in G1. This nuclear import-dependent folding program includes cohesin and factors involved in transcription and RNA processing. The combined and inter-dependent action of chromosome-intrinsic and cytoplasmic inherited folding programs determines the interphase chromatin conformation as cells exit mitosis.
Project description:DNA replicates once per cell cycle. Interfering with the regulation of DNA replication initiation generates genome instability through over-replication and has been linked to early stages of cancer development. Here, we engineered genetic systems in budding yeast to induce unscheduled replication in the G1-phase of the cell cycle. Unscheduled G1 replication initiated at canonical S-phase origins. We quantified the composition of replisomes in G1- and S-phase and identified firing factors, polymerase alpha, and histone supply as factors that limit replication outside S-phase. G1 replication per se did not trigger cellular checkpoints. Subsequent replication during S-phase, however, resulted in over-replication and led to chromosome breaks and chromosome-wide, strand-biased occurrence of RPA-bound single-stranded DNA indicating head-to-tail replication collisions as a key mechanism generating genome instability upon G1 replication. Low-level, sporadic induction of G1 replication induced an identical response, indicating findings from synthetic systems are applicable to naturally occurring scenarios of unscheduled replication initiation.
Project description:In the budding yeast, HMR, HML, telomere and rDNA domain are known as a silencing region. Sir2 need to make it at rDNA and, HMR, HML and the telomere need to Sir2, Sir3, Sir4 complex to control internal gene repression. In this report, we found a newly Sir3 binding domain, CN domain (Chromosome New region) 1~14, by the ChIP on chip analysis on S.cerevisiae chromosome. In addition, we also performed ChIP on chip analysis with anti-Sir3 antibody using G1 phase synchronized cell to find Sir3 distribution difference of stage of cell cycle and we found CN15~CN25 which was G1 phase specific Sir3 binding region. Furthermore, we analyzed difference of gene expression at CN region in sir3 strain, and some regions did not change level of gene expression. In the conventional report, Sir3 had recruited by Sir2 and Sir4 on chromosome, but recruit of Sir3 was independent on Sir2 and Sir4 at some CN regions. These data suggested that we found a newly Sir3 function and Sir3 recruited system on chromosome.
Project description:Chromatin accessibility in the nucleus is a predictor of gene expression, cell division and cell type specificity. NicE-viewSeq (Nicking Enzyme assisted viewing and Sequencing) allows accessible chromatin visualization and sequencing with lower mitochondrial DNA and duplicated sequences compared to ATACsee. Using NicE-viewSeq we interrogated cell cycle G1, S and G2M specific accessible chromatin in mammalian cells. Despite DNA replication and subsequent condensation of chromatin to chromosome, chromatin accessibility remained subtly altered and generally preserved. Genome-wide alteration of accessibility for TSS and enhancer gradually decreased as the cell progressed from G1 to G2M, with distinctive differential accessibility near consensus transcription factors sites. Inhibition of histone deacetylase promoted accessible chromatin of the gene body, correlating with apoptotic gene expression. In addition, reduced chromatin accessibility for MYC oncogene pathway correlated with gene down regulation. Surprisingly, repetitive RNA expression remained unaltered following histone acetylation mediated increased accessibility. Therefore, we suggest that subtle changes in chromatin accessibility is a prerequisite during cell cycle and histone deacetylase inhibitor mediated therapeutics.
Project description:Sequencing of mononucleosomal DNA during G1 and S phases in Saccharomyces cerevisiae Samples from mononucleosomal DNA from WT and rpd3 mutant strains (W303-1a background) in G1 or in S phase in the presence of 0.2 M HU were sequenced (Illumina Genome Analyzer IIx) using the single-end read protocol
Project description:Identity-specific interphase chromosome conformation must be re-established each time a cell divides. To understand how interphase folding is inherited, we developed an experimental approach that segregates chromosome-intrinsic factors from those inherited through the cytoplasm during the establishment of G1 nuclear architecture. Endogenous RanGAP1 or Nup93 proteins were degraded in pro-metaphase arrested DLD-1 cells to prevent the establishment of nucleo-cytoplasmic transport during mitotic exit and isolate the decondensing mitotic chromatin of G1 daughter cells from the cytoplasm. Using this approach, we uncovered a transient folding intermediate entirely driven by chromosome-intrinsic factors. In addition to conventional compartmental segregation, this chromosome-intrinsic folding program leads to prominent genome-scale microcompartmentalization of mitotically bookmarked and cell type-specific cis-regulatory elements. The microcompartment conformation is formed during telophase and subsequently modulated by a second folding program driven by factors inherited through the cytoplasm in G1. The nuclear import-dependent folding program includes cohesin and factors involved in transcription and RNA processing. The combined and inter-dependent action of chromosome-intrinsic and cytoplasmic inherited folding programs determines the interphase chromatin conformation as cells exit mitosis.
Project description:Here we apply single cell bisulfite sequencing to detect epigenetic and genetic changes that occur in BRAF V600E cells that escape G1 arrest and return to the cell cycle during treatment with the MEK inhibitor selumetinib. We detect no major changes in DNA methylation, but find that cells in G2 are enriched in large amplifications and deletions that we ascribe to abnormal mitotic chromosome segregation.