Genome-wide kinetics of DNA excision repair in relation to chromatin state and mutagenesis
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ABSTRACT: We recently developed a high-resolution genome wide assay for mapping DNA excision repair named eXcision Repair-sequencing (XR-seq) (GEO accession: GSE67941) We have now used this assay to assay the effect of chromatin state on DNA repair. Here we report the results of a time-course of the repair of the UV induced damages cyclobutane pyrimidine dimers (CPDs) and (6-4) pyrimidine-pyrimidone photoproducts [(6-4)PPs] in normal human skin fibroblasts. Comparison of this data to histone modification and DNA-seq maps (ENCODE) revealed initial repair of both damages is enriched in open and active chromatin states, whereas repair in heterochromatic and repressed chromatin states is relatively low and persists to later time points. We performed XR-seq for two types of UV induced damages (CPD and (6-4)PP) at multiple time points after UV irradiation, in normal NHF1, and CS-B (CS1ANps3g2, GM16095) fibroblast cell lines. Two biological replicates were performed for each experiment in which independent independent cell populations were UV treated and subjected to XR-seq. For assaying CPD repair, cells were irradiated with 10J/m2 and for assaying (6-4)PP cells were irradiated with 20J/m2. Raw data for the 1h time points of (6-4)PP repair are the same as in GEO accession GSE67941).
Project description:We developed a method for genome-wide mapping of DNA excision repair named XR-seq (eXcision Repair-seq). Human nucleotide excision repair generates two incisions surrounding the site of damage, creating a ~30-mer. In XR-seq, this fragment is isolated and subjected to high-throughput sequencing. We used XR-seq to produce stranded, nucleotide-resolution maps of repair of two UV-induced DNA damages in human cells, cyclobutane pyrimidine dimers (CPDs) and (6-4) pyrimidine-pyrimidone photoproducts ((6-4)PPs). In wild-type cells, CPD repair was highly associated with transcription, specifically with the template strand. Experiments in cells defective in either transcription-coupled excision repair or general excision repair isolated the contribution of each pathway to the overall repair pattern, and showed that transcription-coupled repair of both photoproducts occurs exclusively on the template strand. XR-seq maps capture transcription-coupled repair at sites of divergent gene promoters and bi-directional eRNA production at enhancers. XR-seq data also uncovered the repair characteristics and novel sequence preferences of CPDs and (6-4)PPs. XR-seq and the resulting repair maps will facilitate studies of the effects of genomic location, chromatin context, transcription, and replication on DNA repair in human cells. We have performed XR-seq for two types of UV-induced damages (CPD and (6-4)PP) in three different cell lines: NHF1, XP-C (XP4PA-SV-EB, GM15983)), and CS-B (CS1ANps3g2, GM16095). Two biological replicates were performed for each experiment, in which independent cell populations were UV treated and subjected to XR-seq.
Project description:UV-induced DNA lesions are an important contributor to mutagenesis and cancer, but it is not fully understood how the chromosomal landscape influences UV lesion formation and repair. We have used a novel high-throughput sequencing method to precisely map UV-induced cyclobutane pyrimidine dimers (CPDs) at nucleotide resolution throughout the yeast genome. Analysis of CPD formation reveals that nucleosomal DNA having an inward rotational setting is protected from CPD lesions. In strongly positioned nucleosomes, this nucleosome 'photofootprint' overrides intrinsic dipyrimidine sequence preferences for CPD formation. CPD formation is also inhibited by DNA-bound transcription factors, in effect protecting important DNA elements from UV damage. Analysis of CPD repair revealed a clear signature of efficient transcription-coupled nucleotide excision repair. Repair was less efficient at translational positions near a nucleosome dyad and at heterochromatic regions in the yeast genome. These findings define the roles of nucleosomes and transcription factors in UV damage formation and repair. UV mapping data was analyzed for yeast cells irradiated with 125J/m2 and allowed to repair for 0hr (2 samples), 20 minutes, 1 hour, or 2 hours. Data is also included for naked DNA irradiated with UV 60 or 90 J/m2
Project description:Rad16 is required for global genomic nucleotide excision repair (GG-NER) of UV-induced CPD lesions. Here we have used a novel high-throughput sequencing method known as CPD-seq to map the repair of UV-induced cyclobutane pyrimidine dimers (CPDs) at single nucleotide resolution across the yeast genome in rad16 mutant cells. Analysis of CPD repair indicates that rad16 is generally required for CPD repair in the non-transcribed strand (NTS) of yeast genes and non-transcribed genomic regions.
Project description:UV-induced DNA lesions are an important contributor to mutagenesis and cancer, but it is not fully understood how the chromosomal landscape influences UV lesion formation and repair. We have used a novel high-throughput sequencing method to precisely map UV-induced cyclobutane pyrimidine dimers (CPDs) at nucleotide resolution throughout the yeast genome. Analysis of CPD formation reveals that nucleosomal DNA having an inward rotational setting is protected from CPD lesions. In strongly positioned nucleosomes, this nucleosome 'photofootprint' overrides intrinsic dipyrimidine sequence preferences for CPD formation. CPD formation is also inhibited by DNA-bound transcription factors, in effect protecting important DNA elements from UV damage. Analysis of CPD repair revealed a clear signature of efficient transcription-coupled nucleotide excision repair. Repair was less efficient at translational positions near a nucleosome dyad and at heterochromatic regions in the yeast genome. These findings define the roles of nucleosomes and transcription factors in UV damage formation and repair.
Project description:Here, we describe a genome-wide map of photoreactivation repair of UV-induced cyclobutane pyrimidine dimers (CPDs) in yeast (Saccharomyces cerevisiae) by the endogenous yeast CPD photolyase. CPDs were mapped at single nucleotide resolution across the yeast genome using the CPD-seq method immediately after UV radiation (0min) and following 30 or 60min photoreactivation with UVA light. Photoreactivation repair by photolyase was mapped in both wild-type yeast and rad14∆ cells deficient in nucleotide excision repair (NER). We used these data to analyze CPD repair by photolyase in yeast genes, nucleosomes, and transcription factor binding sites.
Project description:Here, we describe a new genome-wide map of UV-induced cyclobutane pyrimidine dimers (CPDs) in Drosophila S2 cells and a naked DNA control using CPD-seq. We used this data to analyze CPD formation in nucleosomes and different chromatin states across the Drosophila genome. We analyzed CPD formation alongside existing excision repair-sequencing (XR-seq) data to compare CPD damage and repair rates in five distinct chromatin types in Drosophila. This analysis revealed that CPD repair varied in different chromatin domains, while CPD formation was largely unaffected. Moreover, we observed distinct patterns of repair activity in nucleosomes in different chromatin types.
Project description:The rates at which lesions are removed by DNA repair can vary widely throughout the genome with important implications for genomic stability. We measured the distribution of nucleotide excision repair (NER) rates for UV induced lesions throughout the yeast genome. By plotting these repair rates in relation to all ORFs and their associated flanking sequences, we reveal that in normal cells, genomic repair rates display a distinctive pattern, suggesting that DNA repair is highly organised within the genome. We compared genome-wide DNA repair rates in wild type and in RAD16 deleted cells, which are defective in the global genome-NER (GG-NER) sub-pathway, demonstrating how this alters the normalâ¨distribution of NER rates throughout the genome. We examine the genomic locations of global genome NER factor binding in chromatin before and after UV irradiation, and reveal that GG-NER is organized and initiated from specific locations. By controlling the chromatin occupancy of the histone acetyl transferase Gcn5, the GG-NER complex regulates the histone H3 acetylation status and chromatin structure in the vicinity of these genomic sites to promote the efficient DNA repair of UV induced lesions. This demonstrates that chromatin remodeling during the GG-NER process is organized into domains in the genome. Importantly, we demonstrate that deleting the histone modifier GCN5, an accessory factor required for chromatin remodeling during GG-NER, significantly alters the genomic distribution of NER rates. These observations could have important implications for the effect of histone and chromatin modifiers on the distribution of genomic mutations acquired throughout the genome.
Project description:Noncoding mutation hotspots have been identified in melanoma and many of them occur at the binding sites of E26 transformation-specific (ETS) proteins; however, their formation mechanism and functional impacts are not fully understood. Here, we used UV damage sequencing data and analyzed cyclobutane pyrimidine dimer (CPD) formation, DNA repair, and CPD deamination in human cells at single-nucleotide resolution. Our data shows prominent CPD hotspots immediately after UV irradiation at ETS binding sites, particularly at sites with a conserved TTCCGG motif, which correlate with mutation hotspots identified in cutaneous melanoma. Additionally, CPDs are repaired slower at ETS binding sites than in flanking DNA. Cytosine deamination in CPDs to uracil is suggested as an important step for UV mutagenesis. However, we found that CPD deamination is significantly suppressed at ETS binding sites, particularly for the CPD hotspot on the 5’ side of the ETS motif, arguing against a role for CPD deamination in promoting ETS-associated UV mutations. Finally, we analyzed a subset of frequently mutated promoters, including the ribosomal protein genes RPL13A and RPS20, and found that mutations in the ETS motif can significantly reduce the promoter activity. Thus, our data identifies high UV damage and low repair, but not CPD deamination, as the main mechanism for ETS-associated mutations in melanoma and uncover new roles of often-overlooked mutation hotspots in perturbing gene transcription.
Project description:Elf1 is an important transcription elongation factor that has been implicated in transcription coupled-nucleotide excision repair (TC-NER). Here, we have used a high-throughput sequencing method known as CPD-seq to map the repair of UV-induced cyclobutane pyrimidine dimers (CPDs) at single nucleotide resolution across the yeast genome in elf1 mutant cells. Analysis of CPD repair indicates that Elf1 is important for CPD repair in the transcribed strand (TS) of yeast genes, indicating it plays an important role in TC-NER.
Project description:Nucleotide excision repair is a primary DNA repair mechanism that removes bulky DNA adducts such as UV-induced pyrimidine dimers. Correspondingly, genome-wide mapping of nucleotide excision repair with eXcision Repair sequencing (XR-seq), provides comprehensive profiling of DNA damage repair. A number of XR-seq experiments at a variety of conditions for different damage types revealed heterogenous repair in the human genome. Although human repair profiles were extensively studied, how repair maps vary between primates is yet to be investigated. Here, we characterized the genome-wide UV-induced damage repair maps of the grey mouse lemur,Microcebus murinus, in comparison with human. We derived fibroblast cell lines from mouse lemur and exposed them to UV irradiation. Following repair events were captured genome-wide by XR-seq protocol 1 hour and 5 minutes after irradiation for cyclobutane pyrimidine dimers (CPD) and 6-4 pyrimidine-pyrimidone photoproducts ([6-4]PP), respectively. Mouse lemur repair profiles were analyzed in comparison with the equivalent human fibroblast datasets. We found that transcription-coupled repair levels for CPD repair differs between two primates. Despite this, comparative analysis of human and mouse lemur fibroblasts revealed that genome-wide repair profiles of the homologous regions between the primates are highly correlated. This correlation is stronger for the highly expressed genes as well as the genes sharing high homology. With the inclusion of an additional XR-seq sample derived from another human cell line in the analysis, we found that fibroblasts between two primates repair lesions more similarly relative to two distinct cell lines from human. These results suggest that mouse lemurs and humans, and possibly primates in general, share similar repair mechanism as well as genomic variance distribution.