Project description:We recently developed high-throughput sequencing approaches, eXcision Repair sequencing (XR-seq) and Damage-seq, to generate genome-wide mapping of DNA damage formation and excision repair, respectively, with single-nucleotide resolution. Here, we adopted time-course XR-seq data to profile UV-induced excision repair dynamics, paired with Damage-seq data to quantify the overall induced DNA damage. We identified genome-wide repair hotspots that are subject to exemplified amount of repair very soon after UV irradiation. We show that such repair hotspots do not result from hypersensitivity to DNA damage and are thus not damage hotspots. We find that the earliest repair occur preferentially in promoters and enhancers from open-chromatin regions. The repair hotspots are also significantly enriched for frequently interacting regions and super-enhancers, both of which are hotspots for local chromatin interactions. We further extend the interrogation of chromatin organization to DNA replication timing and conclude that early-repair hotspots are enriched for early-replication domains. Collectively, we report genome-wide early-repair hotspots of UV-induced damage, in association with chromatin states and epigenetic compartmentalization of the human genome.
Project description:Meiotic recombination, crucial for proper chromosome segregation and genome evolution, is initiated by programmed DNA double-strand breaks (DSBs) in budding and fission yeasts and likely all sexually reproducing species. In fission yeast, DSBs occur up to several hundred times more frequently at special sites, called hotspots, than in other regions of the genome. What distinguishes hotspots from cold regions is a major unsolved problem, although transcription factors determine some hotspots. We report here the discovery that three coiled-coil proteins -- Rec25, Rec27, and Mug20 -- bind essentially all hotspots with unprecedented, high specificity even without DSB formation. These small proteins are components of linear elements, are related to synaptonemal complex proteins, and are essential for nearly all DSBs at most hotspots. Our results indicate that these hotspot determinants activate or stabilize the DSB-forming protein Rec12 (Spo11 homolog) rather than promote its binding to hotspots. We propose here a new paradigm for hotspot determination and crossover control by linear element proteins.
Project description:Meiotic recombination, crucial for proper chromosome segregation and genome evolution, is initiated by programmed DNA double-strand breaks (DSBs) in budding and fission yeasts and likely all sexually reproducing species. In fission yeast, DSBs occur up to several hundred times more frequently at special sites, called hotspots, than in other regions of the genome. What distinguishes hotspots from cold regions is a major unsolved problem, although transcription factors determine some hotspots. We report here the discovery that three coiled-coil proteins -- Rec25, Rec27, and Mug20 -- bind essentially all hotspots with unprecedented, high specificity even without DSB formation. These small proteins are components of linear elements, are related to synaptonemal complex proteins, and are essential for nearly all DSBs at most hotspots. Our results indicate that these hotspot determinants activate or stabilize the DSB-forming protein Rec12 (Spo11 homolog) rather than promote its binding to hotspots. We propose here a new paradigm for hotspot determination and crossover control by linear element proteins.
Project description:Targeted protein degradation is a novel pharmacology established by drugs that recruit target proteins to E3 ubiquitin ligases. Based on the structure of the degrader and the target, different E3 interfaces are critically involved, thus forming defined "functional hotspots". Understanding disruptive mutations in functional hotspots informs on the architecture of the assembly, and highlights residues susceptible to acquire resistance phenotypes. Here, deep mutational scanning revealed hotspots that are conserved or specific for chemically distinct degraders and targets and validated hotspots mutated in patients that relapse from degrader treatment.
Project description:To determine meiotic recombination initiation sites in Arabidopsis thaliana genome we purified and sequenced oligonucleotides (35-45 nt) bound to SPO11-1, meiosis specific transesterase that induces meiotic DSB formation. This reveals that SPO11-1-oligonucleotide hotspots occur at nucleosome depleted regions of gene promoters, introns, terminators and specific families of DNA transposons (recomposons). To investigate the influence of chromatin structure and epigenetic factors on meiotic DSB formation we performed sequencing of SPO11-1-oligonucleotides in arp6, met1 and suvh4 suvh5 suvh6.
Project description:Mistakes in the maintenance of CG methylation is a source of heritable epimutations in plants. Multigenerational surveys indicate that the rate of these stochastic events varies substantially across the genome, with some regions harboring localized “epimutation hotspots”. Using Arabidopsis as a model, we show that epimutation hotspots are indexed by a specific set of chromatin states (CS) that map to sub-regions of gene body methylation genes. Although these regions comprise only ~12% of all CGs in the genome, they account for ~63% of all epimutation events per unit time. Molecular profiling revealed that these regions contain unique sequence features, harbor steady-state intermediate methylation levels, and act as putative targets of antagonistic DNA methylation pathways. We further demonstrate that experimentally-induced shifts in steady-state methylation in these hotspot regions are sufficient to significantly alter local epimutation intensities. Our work thus lays foundation for dissecting the molecular mechanisms of epimutation hotspots in plants.