Homo sapiens
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ABSTRACT:
PROVIDER: PRJNA961772 | ENA |
REPOSITORIES: ENA
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Project description:FFPE DNA shows two major error profiles derived from deamination of cytosine and methylcytosine that can be mitigated using distinct repair strategies
| PRJEB57418 | ENA
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:Transition of cytosine to thymine in CpG dinucleotides is the most frequent type of mutation in cancer. This increased mutability is commonly attributed to the spontaneous deamination of 5-methylcytosine (5mC), which is normally repaired by the base-excision repair (BER) pathway. However, the contribution of 5mC deamination in the increasing diversity of cancer mutational signatures remains poorly explored. Here, we integrate mutational signatures analysis in a large series of tumor whole genomes with lineage-specific epigenomic data to draw a detailed view on 5mC deamination in cancer. We uncover tumor type-specific patterns of 5mC deamination signatures in CpG and non-CpG contexts. We demonstrate that the BER glycosylase MBD4 preferentially binds to active chromatin and early replicating DNA, which correlates with lower mutational burden in these domains. We validate our findings by modeling BER deficiencies in isogenic cell models. Overall, we establish MBD4 as the main actor responsible for 5mC deamination repair in humans.
2024-09-12 | GSE275181 | GEO
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: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: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:N 4-methylcytosine (4mC) is a natural DNA modification occurring in thermophiles and plays important roles in restriction-modification (R-M) systems in bacterial genomes. However, the precise location and sequence context of 4mC in the whole genome are limited. In this study, we developed an APOBEC3A-mediated deamination sequencing (4mC-AMD-seq) method for genome-wide mapping of 4mC at single-base resolution. In the 4mC-AMD-seq method, cytosine and 5-methylcytosine (5mC) are deaminated by APOBEC3A (A3A) protein to generate uracil and thymine, both of which are read as thymine in sequencing, while 4mC is resistant to deamination and therefore read as cytosine. Thus, the readouts of cytosines from sequencing could manifest the original 4mC sites in genomes. With the 4mC-AMD-seq method, we achieved the genome-wide mapping of 4mC in Deinococcus radiodurans (D. radiodurans). In addition, we confirmed that 4mC, but not 5mC, was the major modification in the D. radiodurans genome. We identified 1586 4mC sites in the genome of D. radiodurans, among which 564 sites were located in the CCGCGG motif. The average methylation levels in the CCGCGG motif and non-CCGCGG sequence were 70.0% and 22.8%, respectively. We envision that the 4mC-AMD-seq method will facilitate the investigation of 4mC functions, including the 4mC-involved R-M systems, in uncharacterized but potentially useful strains.
2021-12-15 | GSE189965 | GEO
Project description:5-Methylcytosine (5mC) is a crucial epigenetic modification plays a significant role in the regulation of gene expression. Accurate and quantitative detection of 5mC at single-base resolution is essential for understanding its epigenetic functions within genomes. In this study, we develop a novel nTET-assisted deaminase sequencing (TAD-seq) method for the base-resolution and quantitative detection of 5mC in genomic DNA. The TAD-seq method utilizes a Naegleria TET-like dioxygenase (nTET) to oxidize 5mC, generating 5-methylcytosine oxidation products (5moC). We also engineered a variant of the human apolipoprotein B mRNA-editing catalytic polypeptide-like 3A (A3A), creating an A3A mutant (A3Am). Treatment with A3Am results in the conversion of cytosine to uracil, while 5moC remains unchanged. Consequently, TAD-seq enables the direct deamination of cytosine to uracil by A3Am, which is sequenced as thymine, whereas 5mC, once oxidized to 5moC by nTET, resists deamination and is sequenced as cytosine. Therefore, the cytosines that persist in the sequencing data represent the original 5mC sites. We applied TAD-seq to HEK293T cells, generating a base-resolution map of 5mC that exhibits strong concordance with maps generated by conventional BS-seq. TAD-seq emerges as a powerful, bisulfite-free approach for the single-base resolution mapping of 5mC stoichiometry in genomic DNA.
2024-06-30 | GSE254203 | GEO
Project description:Here we present APOBEC-coupled epigenetic sequencing (ACE-seq), a bisulfite-free method for localizing 5-hydroxymethylcytosine (5hmC) at single-base resolution with low DNA input. The method builds on the observation that AID/APOBEC family DNA deaminase enzymes can potently discriminate between cytosine modification states and exploits the non-destructive nature of enzymatic, rather than chemical, deamination. ACE-seq yielded high-confidence 5hmC profiles with at least 1,000-fold less DNA input than conventional methods. Applying ACE-seq to generate a base-resolution map of 5hmC in tissue-derived cortical excitatory neurons, we found that 5hmC was almost entirely confined to CG dinucleotides. The whole-genome map permitted cytosine, 5-methylcytosine (5mC) and 5hmC to be parsed and revealed genomic features that diverged from global patterns, including enhancers and imprinting control regions with high and low 5hmC/5mC ratios, respectively. Enzymatic deamination overcomes many challenges posed by bisulfite-based methods, thus expanding the scope of epigenome profiling to include scarce samples and opening new lines of inquiry regarding the role of cytosine modifications in genome biology.
2018-10-08 | GSE116016 | GEO