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: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:UV light is an initiating factor in the etiology of human melanoma due to its production of mutagenic DNA photoproducts, primarily cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts. UV-induced mutations are heterogeneously distributed across melanoma genomes, being enriched, for example, in regions of compact heterochromatin and at active transcription factor binding sites (TFBS). Differential ability of nucleotide excision repair (NER) to remove UV-induced DNA lesions in these regions has been proposed as the primary factor establishing the observed regional differences in melanoma mutation density. However, it is not fully understood to what extent the binding of transcription factors and chromatin structure affect UV damage formation, nor how variations in initial damage levels contribute to mutagenesis. Here, we directly mapped sites of CPD formation across the genome in human cells, and show that variations in UV damage formation, due to primary chromatin structure and transcription factor binding, are strongly correlated with local differences in melanoma mutation density. Analysis of individual transcription factors revealed that the E26 transformation-specific (ETS) family is the major contributor to increased somatic mutation density at TFBS in melanoma, primarily because DNA binding by ETS family transcription factors stimulates the formation of CPD lesions, generating UV damage 'hotspots'. Moreover, many ETS binding sites, including those associated with known cancer genes, are recurrently mutated in human melanomas. These findings establish variable lesion formation as a key contributor to mutation heterogeneity in cancer.
Project description:We used a high-throughput sequencing method known as CPD-seq to map the formation of UV-induced cyclobutane pyrimidine dimers (CPD) at single nucleotide resolution in UV-irradiated yeast genomic DNA (naked DNA) in the presence or absence of cytosine methylation at CpG sites by the methyltransferase M.SssI.
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: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: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:UV-induced CPDs were mapped in primary skin melanocytes or normal human skin fibroblasts following either UVC or UVB irradiation and in isolated human genomic DNA (naked DNA control) that was UVB or UVC irradiated. CPDs were mapped across the human genome using the CPD-capture-seq method and the resulting libraries were captured for ~4000 genomic regions of interest (~3 Mbp) of the human genome by the company Rapid Genomics prior to Illumina sequencing