Project description:TFIIH is a 10-protein complex that is conserved through out eukaryotes. TFIIH has two primary cellular functions: transcription initiation and nucleotide excision repair (NER). In transcription initiation, TFIIH acts as a structural scaffold, phosphorylates the RNA polymerase II (pol II) C-terminal domain (CTD) and translocates promoter DNA through the pol II active site to facilitate start site selection. In NER, again is a structural scaffold, opens a bubble around damaged DNA and scans the damaged strand for bulky lesions. In yeast (Saccharomyces cerevisiae), TFIIH is composed of the two helicases Ssl2 and Rad3, the scaffolding subunits Tfb1, Tfb2, Tfb4 and Ssl1 and the kinase subunits Kin28, Ccl1 and Tfb3.
Project description:To recognize DNA damage, nucleotide excision repair (NER) deploys a multipart mechanism by which the XPC sensor detects helical distortions followed by engagement of TFIIH for lesion verification. Accessory players ensure that this factor handover takes place on chromatin where DNA is wrapped around histones. We show that the histone methyltransferase ASH1L, once activated by MRG15, accelerates global-genome NER activity. Upon UV irradiation, ASH1L deposits H3K4me3 marks all over the genome (except in gene promoters), thus priming chromatin for relocations of XPC from native to damaged DNA. ASH1L further recruits the histone chaperone FACT to UV lesions. In the absence of ASH1L, MRG15 or FACT, XPC persists on damaged DNA without being able to deliver lesions to the TFIIH verifier. We conclude that ASH1L implements repair hotspots whose H3K4me3 and FACT occupancy confers an active promoter-like code and organization of histones that make DNA damage verifiable by the NER machinery.
Project description:To recognize DNA damage, nucleotide excision repair (NER) deploys a multipart mechanism by which the XPC sensor detects helical distortions followed by engagement of TFIIH for lesion verification. Accessory players ensure that this factor handover takes place on chromatin where DNA is wrapped around histones. We show that the histone methyltransferase ASH1L, once activated by MRG15, accelerates global-genome NER activity. Upon UV irradiation, ASH1L deposits H3K4me3 marks all over the genome (except in gene promoters), thus priming chromatin for relocations of XPC from native to damaged DNA. ASH1L further recruits the histone chaperone FACT to UV lesions. In the absence of ASH1L, MRG15 or FACT, XPC persists on damaged DNA without being able to deliver lesions to the TFIIH verifier. We conclude that ASH1L implements repair hotspots whose H3K4me3 and FACT occupancy confers an active promoter-like code and organization of histones that make DNA damage verifiable by the NER machinery.
Project description:To recognize DNA damage, nucleotide excision repair (NER) deploys a multipart mechanism by which the XPC sensor detects helical distortions followed by engagement of TFIIH for lesion verification. Accessory players ensure that this factor handover takes place on chromatin where DNA is wrapped around histones. We show that the histone methyltransferase ASH1L, once activated by MRG15, accelerates global-genome NER activity. Upon UV irradiation, ASH1L deposits H3K4me3 marks all over the genome (except in gene promoters), thus priming chromatin for relocations of XPC from native to damaged DNA. ASH1L further recruits the histone chaperone FACT to UV lesions. In the absence of ASH1L, MRG15 or FACT, XPC persists on damaged DNA without being able to deliver lesions to the TFIIH verifier. We conclude that ASH1L implements repair hotspots whose H3K4me3 and FACT occupancy confers an active promoter-like code and organization of histones that make DNA damage verifiable by the NER machinery.
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: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.
Project description:Nucleotide excision repair (NER) counteracts the onset of cancer and aging by removing helix-distorting DNA lesions via a ‘cut-and-patch’-type reaction. The regulatory mechanisms that drive NER through its successive damage recognition, verification, incision and gap restoration reaction steps remain elusive. Here we show that the RAD5-related translocase HLTF facilitates repair through active eviction of incised damaged DNA together with associated repair proteins. Our data shows a dual incision-dependent recruitment of HLTF to the NER incision complex, mediated by HLTF’s HIRAN domain that binds 3’-OH single-stranded DNA ends. HLTF’s translocase motor subsequently promotes dissociation of incised oligonucleotides together with members of the stably damage-bound incision complex to allow efficient PCNA loading and initiation of repair synthesis. Our findings uncover HLTF as an important NER factor that actively evicts DNA damage, thereby providing an additional quality control by coordinating the transition between the excision and DNA synthesis steps to safeguard genome integrity.
Project description:The role of sirtuin family in regulating DNA DSB repair has been extensively investigated, and here, we explore the molecular mechanisms of Sirtuin family in nucleotide excision repair.
Project description:Embryonic stem cells can self-renew and differentiate, holding great promise for regenerative medicine. They also employ multiple mechanisms to preserve the integrity of their genomes. Nucleotide excision repair, a versatile repair mechanism, removes bulky DNA adducts from the genome. However, the dynamics of the capacity of nucleotide excision repair during stem cell differentiation remain unclear. Here, using immunoslot blot assay, we measured repair rates of UV-induced DNA damage during differentiation of human embryonic carcinoma (NTERA-2) cells into neurons and muscle cells. Our results revealed that the capacity of nucleotide excision repair increases as cell differentiation progresses. We also found that inhibition of the apoptotic signaling pathway has no effect on nucleotide excision repair capacity. Furthermore, RNA-seq-based transcriptomic analysis indicated that expression levels of four core repair factors, xeroderma pigmentosum (XP) complementation group A (XPA), XPC, XPG, and XPF-ERCC1, are progressively up-regulated during differentiation, but not those of replication protein A (RPA) and transcription factor IIH (TFIIH). Together, our findings reveal that increase of nucleotide excision repair capacity accompanies cell differentiation, supported by the up-regulated transcription of genes encoding DNA repair enzymes during differentiation of two distinct cell lineages.
Project description:ERCC1 is a DNA endonuclease participating in the Nucleotide Excision Repair (NER) pathway. Its functionality is related to XPF; the two proteins work as a heterodimer to incise the 5 of a 30-mer that contains the damaged nucleotide and remove the fragment together with XPG. Apart from NER deficiency, mutated Ercc1 in mice and humans causes a series of progeroid symptoms (premature ageing). We hypothesize that there are undescribed functions of ERCC1, possibly in transcriptional regulation that contribute to the development of the striking phenotypes observed. The aim is to identify previously uncharacterized protein partners of ERCC1 that might contribute to our understanding of its differential roles during DNA damage-driven progeria.