Project description:Non-coding RNA has a proven ability to direct and regulate chromatin modifications by acting as scaffolds between DNA and histone-modifying complexes. However, it is unknown if ncRNA plays any role in DNA replication and epigenome maintenance, including histone eviction and re-instalment of histone-modifications after genome duplication. Isolation of nascent chromatin has identified a large number of RNA-binding proteins in addition to unknown components of the replication and epigenetic maintenance machinery. Here, we isolated and characterized long and short RNAs associated with nascent chromatin at active replication forks and track RNA composition during chromatin maturation across the cell cycle. Shortly after fork passage, GA-rich-, Alpha repeats and TERRA RNA are associated with replicated DNA. These repeat RNAs arise from loci undergoing replication, suggesting an interaction in cis. Post-replication during chromatin maturation, and even after mitosis in G1, the repeats remain enriched on DNA. This argues that specific types of repeat RNAs are transcribed shortly after DNA replication and stably associates with their loci of origin throughout cell cycle. Our rich data set provides a resource to understand how repeat RNAs and their engagement with chromatin are regulated with respect to DNA replication and across the cell cycle.
Project description:Non-coding RNA has a proven ability to direct and regulate chromatin modifications by acting as scaffolds between DNA and histone-modifying complexes. However, it is unknown if ncRNA plays any role in DNA replication and epigenome maintenance, including histone eviction and re-instalment of histone-modifications after genome duplication. Isolation of nascent chromatin has identified a large number of RNA-binding proteins in addition to unknown components of the replication and epigenetic maintenance machinery. Here, we isolated and characterized long and short RNAs associated with nascent chromatin at active replication forks and track RNA composition during chromatin maturation across the cell cycle. Shortly after fork passage, GA-rich-, Alpha repeats and TERRA RNA are associated with replicated DNA. These repeat RNAs arise from loci undergoing replication, suggesting an interaction in cis. Post-replication during chromatin maturation, and even after mitosis in G1, the repeats remain enriched on DNA. This argues that specific types of repeat RNAs are transcribed shortly after DNA replication and stably associates with their loci of origin throughout cell cycle. Our rich data set provides a resource to understand how repeat RNAs and their engagement with chromatin are regulated with respect to DNA replication and across the cell cycle.
Project description:Noncoding RNA has a proven ability to direct and regulate chromatin modifications by acting as scaffolds between DNA and histone-modifying complexes. However, it is unknown if ncRNA plays any role in DNA replication and epigenome maintenance, including histone eviction and reinstallment of histone modifications after genome duplication. Isolation of nascent chromatin has identified a large number of RNA-binding proteins in addition to unknown components of the replication and epigenetic maintenance machinery. Here, we isolated and characterized long and short RNAs associated with nascent chromatin at active replication forks and track RNA composition during chromatin maturation across the cell cycle. Shortly after fork passage, GA-rich-, alpha- and TElomeric Repeat-containing RNAs (TERRA) are associated with replicated DNA. These repeat containing RNAs arise from loci undergoing replication, suggesting an interaction in cis. Post-replication during chromatin maturation, and even after mitosis in G1, the repeats remain enriched on DNA. This suggests that specific types of repeat RNAs are transcribed shortly after DNA replication and stably associate with their loci of origin throughout the cell cycle. The presented method and data enable studies of RNA interactions with replication forks and post-replicative chromatin and provide insights into how repeat RNAs and their engagement with chromatin are regulated with respect to DNA replication and across the cell cycle.
Project description:The regulation of replication forks stalling and replication origins firing must be tightly coordinated to prevents genomic instability. Here we show that GNL3/nucleostemin, a GTP-binding protein able to shuttle between the nucleolus and the nucleoplasm, limits replicative stress by limiting replication origins firing. GNL3 is in proximity of nascent DNA and its depletion reduces forks speed but increases forks density and replication origins firing. When subjected to exogenous replicative stress, cells impaired for GNL3 exhibits MRN-dependent resection and RPA phosphorylation. Strikingly, inhibition of origin firing using CDC7 inhibitor decreased resection in absence of GNL3 but not in absence of BRCA1, suggesting that GNL3 does not protect nascent strand directly from resection. Consistent with this, overexpression of GNL3 leads to an increased resection in response to replicative stress and enhanced origin firing efficiency. These data indicate that the probability of origins firing is tightly regulated by GNL3 to limit replicative stress. Finally, we show that ORC2 and GNL3 interacts together in the nucleolus. We propose a model where GNL3 level is crucial to determine the correct amount of ORC2 on chromatin by sequestrating it in the nucleolus thanks to the capacity of GNL3 to shuttle between nucleoplasm and nucleolus.
Project description:Faithful duplication of DNA is essential for the maintenance of genomic stability in all organisms. DNA synthesis proceeds bi-directionally with continuous synthesis of leading strand DNA and discontinuous synthesis of lagging strand DNA. Herein, we describe a method of enriching and Sequencing of Protein-Associated Nascent strand DNA (eSPAN) to detect whether a protein binds the leading- and lagging-strands of DNA replication forks. We show that Pol-epsilon, PCNA, Cdc45, Mcm6 and Mcm10 preferentially associate with leading strands, whereas Pol-alpha, Pol32, Pol-delta, Rfa1 and Rfc1 associate with lagging strands of hydroxyurea (HU)-stalled replication forks. In contrast, PCNA is enriched at lagging strands of normal replication forks in wild type cells and HU-stalled forks in cells lacking Elg1. These studies demonstrate a strategy to reveal proteins at leading and lagging strands of DNA replication forks, and suggest that the unloading of PCNA from lagging strands of HU-stalled replication forks helps maintain genome integrity. We synchronized yeast cells at G1 and released into early S phase in the presence of BrdU, a nucleotide analog that can be incorporated into newly synthesized DNA strand, and hydroxyurea (HU), a ribonucleotide reductase inhibitor. HU has no effect on initiation of DNA replication at early replication origins, but inhibit late replication firing. In addition, replication forks are stalled due to depletion of dNTPs. We then performed chromatin-immunoprecipitation of 12 proteins of interest following a standard procedure. Protein-bound DNAs were then reverse-crosslinked and double strand DNA was denatured. Nascent DNA was enriched by immunoprecipitation using anti-BrdU antibodies. The recovered ssDNA was first marked with ligation to one oligo at 3M-bM-^@M-^Y end before conversion to dsDNA for library preparation and sequencing. In this way, the directionality of ssDNA and therefore strand information of each sequenced DNA were known. The sequencing tag was mapped to both Watson (red) and Crick (blue) strands of the reference genome. In addition to ChIP-eSPAN, we also performed BrdU-IP and single strand DNA sequence (BrdU-ssSeq) and protein ChIP followed by single-strand DNA sequencing (ChIP-ssSeq) for each corresponding ChIP-eSPAN experiment. We also performed Mcm4 and Mcm6 ChIP-seq using cells synchronized at G1 phase of the cell cycle for identification of replication origins in comparison with published dataset. Some protein ChIP-ssSeq and ChIP-eSPAN experiments were repeated and the data fits well each other. Therefore, we did not repeat all protein ChIP-ssSeq and ChIP-eSPAN experiments.
Project description:Faithful duplication of DNA is essential for the maintenance of genomic stability in all organisms. DNA synthesis proceeds bi-directionally with continuous synthesis of leading strand DNA and discontinuous synthesis of lagging strand DNA. Herein, we describe a method of enriching and Sequencing of Protein-Associated Nascent strand DNA (eSPAN) to detect whether a protein binds the leading- and lagging-strands of DNA replication forks. We show that Pol-epsilon, PCNA, Cdc45, Mcm6 and Mcm10 preferentially associate with leading strands, whereas Pol-alpha, Pol32, Pol-delta, Rfa1 and Rfc1 associate with lagging strands of hydroxyurea (HU)-stalled replication forks. In contrast, PCNA is enriched at lagging strands of normal replication forks in wild type cells and HU-stalled forks in cells lacking Elg1. These studies demonstrate a strategy to reveal proteins at leading and lagging strands of DNA replication forks, and suggest that the unloading of PCNA from lagging strands of HU-stalled replication forks helps maintain genome integrity.
Project description:Deregulation of RNA Polymerase II (RNAPII) by oncogenic signaling leads to collisions of RNAPII with DNA synthesis machinery (transcription-replication conflicts, TRCs). TRCs can result in DNA damage and underlie genomic instability in tumor cells. Here we provide evidence that elongating RNAPII promotes activation of the ATM kinase at TRCs to drive DNA repair. We show the ATPase Wrnip1 that binds and protects stalled replication forks, associates with RNAPII and limits ATM activation. Wrnip1 binding to elongating RNAPII requires catalytic activity of the ubiquitin ligase Huwe1. Mutation of Huwe1 promotes the transfer of Wrnip1 onto replisome and induces TRCs stimulating ATM activation on RNAPII. This mechanism is evoked early upon replicative stress to induce Wrnip1 translocation and ATM signaling at TRCs. Thus, although primarily considered as genotoxic events, TRCs can provide a mechanism to maintain genome stability under replicative stress.