Genome-wide mapping reveals that deoxyuridine is enriched in the human centromeric DNA
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE99011 | GEO | 2018/05/24
REPOSITORIES: GEO
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Project description:Deoxyuridine (dU) in DNA can result from deamination of cytosine and dUMP misincorporation. The easy single-nucleotide resolution assay for dU are crucial to understanding its role in genome. Herein, we present a new concept of “base substitution” for accurate single-nucleotide resolution profiling of dU. The method termed AI-Seq (Artificial Incorporation of a modified nucleobase for sequencing) was developed using artificial cytosine (N3-C) to replace dU. After the artificial base construction, dU can read as cytosine during polymerase chain reaction assay. AI-seq was validated on synthetic DNA and then applied to the genome of HEK293T cell line. Collectively, the “base substitution” provides a novel approach for generating comprehensive information about the distribution of dU and can be potentially adapted to detect other epigenetic modifications.
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Project description:Uracil DNA glycosylases (UDGs) excise uracil from DNA arising from dUMP misincorporation during replication or from cytosine deamination. Besides functioning in canonical uracil repair, UDGs cooperate with DNA base modifying enzymes to effect mutagenesis or DNA demethylation. Mammalian cells express four UDGs, the functional dissection of which represents a challenge. Here, we used Schizosaccharomyces pombe with only two UDGs, Ung1 and Thp1, as a simpler model to study functional interactions in uracil repair. We show that despite a predominance of Ung1 activity in cell extracts, both UDGs act redundantly against genomic uracil accumulation and mutations from cytosine deamination in cells. Notably, Thp1 but not Ung1-dependent repair is cytotoxic under genomic uracil stress induced by 5-fluorouracil exposure or AID expression. Also, Thp1- but not Ung1-mediated base excision is recombinogenic, accounting for more than 60% of spontaneous mitotic recombination events in a recombination assay. Hence, the qualitative outcome of uracil repair depends on the initiating UDG; while Ung1 shows expected features of a bona-fide DNA repair enzyme, Thp1-initiated repair appears slow and non-productive, implicating a function beyond canonical DNA repair. Given the epigenetic role of mammalian TDGs, we performed transcriptome analyses and identified a possible function of Thp1 in stabilizing gene expression.
2014-12-31 | GSE64585 | GEO
Project description:Study hypothesis: Increasing folate status and the MethyleneTetraHydroFolate Reductase (MTHFR) C677T genotype influence intermediary biomarkers of preclinical neoplasia (DeoxyriboNucleic Acid [DNA] methylation and uracil misincorporation) in human colonic epithelium.
Primary outcome(s): Changes in genomic and gene specific DNA methylation and uracil misincorporation.
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Project description:Human APOBEC3 enzymes are a family of single-stranded (ss)DNA and RNA cytidine deaminases that act as part of the intrinsic immunity against viruses and retroelements. APOBEC3s deaminate cytosine to form uracil which can functionally inactivate or cause degradation of viral or retroelement genomes. In addition, APOBEC3 proteins have deamination independent anti-viral activity and aberrant regulation of APOBEC3 expression can result in the deamination and mutagenesis of the genome contributing to cancer initiation and evolution. To further understand their cellular roles, we used affinity purification mass spectrometry (AP-MS) to determine the protein-protein interaction (PPI) network for the human APOBEC3 enzymes and uncovered a diverse number of protein-protein and protein-RNA mediated interactions. PPIs with the Prefoldin family of protein folding chaperones were identified for APOBEC3B, APOBEC3D, and APOBEC3F. The APOBEC3B and prefoldin 5 (PFD5) interaction disrupted the ability of PFD5 to induce degradation of the oncogene cMyc, implicating a deamination independent contribution of APOBEC3B to cancer. Altogether, the results uncover novel functions and interactions of the APOBEC3 family and suggest that they may have fundamental roles in cellular RNA biology, their roles are not redundant, and there is a deamination independent influence on cancer.
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Project description:The hydrolytic deamination of cytosine and 5-methylcytosine drives many of the transition mutations observed in human cancer. The deamination-induced mutagenic intermediates are either uracil or thymine adducts mispaired with guanine. While a substantial array of methods exists to measure other types of DNA adducts, the cytosine deamination adducts pose unusual analytical problems and adequate methods to measure them have not yet been developed. We describe here a novel hybrid thymine DNA glycosylase, hyTDG, which is comprised of a 29-amino acid sequence from human thymine DNA glycosylase linked to a thymine glycosylase found in an archaeal thermophilic bacterium. Using defined-sequence oligonucleotides, we show that hyTDG has robust mispair-selective activity against deaminated U:G and T:G mispairs. We have further developed a method for separating glycosylase-released free bases from oligonucleotides and DNA followed by GC-MS/MS identification and quantification. Using this approach, we have measured for the first time the levels of total Uracil (U), U:G and T:G in calf thymus DNA. The method presented here will allow the measurement of the formation, persistence, and repair of a biologically important class of deaminated cytosine adducts.
2022-02-15 | PXD030459 | Pride
Project description:DNA deamination occurs constantly in a cell and causes DNA damage. As this damage can be deleterious, organisms have evolved many systems to eliminate it. Deamination of cytosine, guanine, adenine, and 5-methylcytosine results in the formation of uracil, xanthine, hypoxanthine, and thymine, respectively. Sodium bisulfite is a kind of DNA deaminating agent that can increase the frequency of DNA deamination in cells. This study measures the transcriptome profile of Haloferax volcanii H26 strain and HVO_RS06830 gene knockout strain, induced with different concentrations of sodium bisulfite.
2024-10-08 | GSE254961 | GEO
Project description:APOBEC-AID family of cytidine deaminase prefers single-stranded nucleic acids for cytidine to uracil deamination. Single-stranded nucleic acids are commonly involved in the DNA repair system for breaks generated by CRISPR-Cas9. Here, we show in human cells that APOBEC3s can trigger the cytidine deamination of single-stranded oligodeoxynucleotides, which ultimately results in base substitution mutations in genomic DNA through the homology-directed repair (HDR) of Cas9-generated double-strand breaks . In addition, the APOBEC3-catalyzed deamination in genomic single-stranded DNA formed during the repair of Cas9 nickase-generated single-strand breaks can be further processed to yield mutations mainly involving insertions or deletions (indels). Mechanistically, both APOBEC3-mediated deamination and DNA repair proteins play important roles in the generation of these indels. Correspondingly, optimizing conditions for the repair of CRISPR-Cas9-generated DNA breaks, such as using double-stranded donors in HDR or temporarily suppressing endogenous APOBEC3s, can substantially repress these unwanted mutations in genomic DNA.
2017-11-10 | GSE105146 | GEO
Project description:Bisulphite (BS) and oxidative bisulphite (oxBS) converted DNA from 4 normal human placentas were hybridized to the Illumina HumanMethylation450 Beadchip v1.2, obtaining the BS and oxBS DNA methylation profiles across approximately 450,000 CpGs. By using the oxBS treatment, the selective chemical oxidation of 5-hydroxymethylcytosine (5hmC) to 5-formylcytosine (5fC) and the deamination of the latter to uracil during the BS conversion allowed the quantification of independent 5-methylcytosine (5mC) and 5hmC methylation levels at every single CpG. In consequence, this data set characterizes the genome-wide distribution of 5hmC in the human placenta offerring a high-confidence list of intervals enriched for 5hmC in this tissue.
2017-09-12 | GSE93429 | GEO
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.
2023-12-01 | GSE235483 | GEO
Project description:5-Hydroxymethylcytosine (5hmC) is an important epigenetic mark that can regulate gene expression. While some methods were developed to detect 5hmC, direct genome-wide mapping of 5hmC at base resolution are still highly desirable. Herein, we proposed a single-step deamination sequencing (SSD-seq) method for the genome-wide mapping of 5hmC at single-base resolution. This method capitalizes on a screened engineered human apolipoprotein B mRNA-editing catalytic polypeptide-like 3A (A3A) protein to produce differential deamination activity toward cytosine (C), 5-methylcytosine (5mC), and 5hmC. In SSD-seq, an engineered A3A protein (eA3A-v10) can adequately deaminate C and 5mC, but not 5hmC. The original C and 5mC in DNA are deaminated by eA3A-v10 to form uracil (U) and thymine (T), both of which are read as T during sequencing. However, 5hmC is resistant to the deamination by eA3A-v10 and is still read as C during sequencing. Therefore, the remaining C in the sequence reads manifests the original 5hmC. Applying SSD-seq to generate a base-resolution map of 5hmC in human lung tissue, we found that 5hmC was almost entirely confined to CpG dinucleotides. The base-resolution map of 5hmC from human lung tissue generated by SSD-seq correlated strongly with that generated by prior ACE-seq. Taken together, the SSD-seq method is single-step, bisulfite-free and does not require DNA glycosylation or chemical treatment, which offers a valuable tool for the direct and quantitative detection of 5hmC in genomes at single-base resolution.
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