Project description:DNA N6-methyladenine (6mA) is the most widespread type of DNA methylation in prokaryotes. However, the prevalence of 6mA in eukaryotes has recently been challenged due to the limitations of current 6mA detection techniques. Here, we present a chemical-based sequencing method, Nitrite-assisted Amino MEthylation sequencing (NAME-seq), for quantitative, whole-genome mapping of 6mA at single-base resolution. NAME-seq combines nitrite conversion of 6mA to nitrosylated-6mA (6mA-NO) with Klenow Fragment (3'→5' exo-) random priming to induce a 6mA-to-T transversion specifically. We apply NAME-seq to two bacterial species and show that, compared to SMRT-seq, NAME-seq results in a more specific and robust detection of 6mA. NAME-seq can also accurately map 6mA in the C. reinhardtii genome at single-base resolution. Additionally, we show that NAME-seq can be combined with conventional DIP-seq to detect 6mA in the Dam-methylated human genome with high specificity. Therefore, we further perform DIP-NAME-seq to profile 6mA in WT and TASOR KO K562 cell line and revealed that 6mA is enriched at specific motifs (HYYHAG and CACACA) and H3K9me3 regions. In summary, we demonstrate NAME-seq is a specific and sensitive sequencing method for quantitative 6mA mapping at single base resolution across different model organisms.
Project description:DNA N6-methyladenine (6mA) is the most widespread type of DNA methylation in prokaryotes. However, the prevalence of 6mA in eukaryotes has recently been challenged due to the limitations of current 6mA detection techniques. Here, we present a chemical-based sequencing method, Nitrite-assisted Amino MEthylation sequencing (NAME-seq), for quantitative, whole-genome mapping of 6mA at single-base resolution. NAME-seq combines nitrite conversion of 6mA to nitrosylated-6mA (6mA-NO) with Klenow Fragment (3'→5' exo-) random priming to induce a 6mA-to-T transversion specifically. We apply NAME-seq to two bacterial species and show that, compared to SMRT-seq, NAME-seq results in a more specific and robust detection of 6mA. NAME-seq can also accurately map 6mA in the C. reinhardtii genome at single-base resolution. Additionally, we show that NAME-seq can be combined with conventional DIP-seq to detect 6mA in the Dam-methylated human genome with high specificity. Therefore, we further perform DIP-NAME-seq to profile 6mA in WT and TASOR KO K562 cell line and revealed that 6mA is enriched at specific motifs (HYYHAG and CACACA) and H3K9me3 regions. In summary, we demonstrate NAME-seq is a specific and sensitive sequencing method for quantitative 6mA mapping at single base resolution across different model organisms.
Project description:Cytosine base modifications 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) are present in mammalian DNA. Here, reduced bisulfite sequencing is developed for quantitatively sequencing 5fC at single-base resolution. This method is then applied with oxidative bisulfite sequencing to gain a map of 5mC, 5hmC and 5fC in mouse embryonic stem cells.
Project description:Recently, the cytosine modifications 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) were found to exist in the genomic deoxyribonucleic acid (DNA) of a wide range of mammalian cell types. It is now important to understand their role in normal biological function and disease. Here we introduce reduced bisulfite sequencing (redBS-Seq), a quantitative method to decode 5fC in DNA at single-base resolution, based on a selective chemical reduction of 5fC to 5hmC followed by bisulfite treatment. After extensive validation on synthetic and genomic DNA, we combined redBS-Seq and oxidative bisulfite sequencing (oxBS-Seq) to generate the first combined genomic map of 5-methylcytosine, 5hmC and 5fC in mouse embryonic stem cells. Our experiments revealed that in certain genomic locations 5fC is present at comparable levels to 5hmC and 5mC. The combination of these chemical methods can quantify and precisely map these three cytosine derivatives in the genome and will help provide insights into their function.
Project description:While N6-methyldeoxyadenine (6mA) modification is a fundamental regulation in prokaryotes, its prevalence and functions in eukaryotes are controversial. Here, we report 6mA-Sniper to quantify 6mA sites in eukaryotes at single-nucleotide resolution, and delineate a 6mA profile in Caenorhabditis elegans with 2034 sites. Twenty-six of 39 events with Mnl I restriction endonuclease sites were verified, demonstrating the feasibility of this method. The levels of 6mA sites pinpointed by 6mA-Sniper are generally increased after Pseudomonas aeruginosa infection, but decreased in strains with the removal of METL-9, the dominant 6mA methyltransferase. The enrichment of these sites on specific motif of [GC]GAG, the selective constrains on them, and their coordinated changes with METL-9 levels thus support an active shaping of the 6mA profile by methyltransferase. Moreover, for regions marked by 6mA sites that emerged after infection, an enrichment of up-regulated genes was detected, possibly mediated through a mutual exclusive cross-talk between 6mA and H3K27me3 modification. We thus highlight 6mA regulation as a previously neglected regulator in eukaryotes.
Project description:Cytosine base modifications 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) are present in mammalian DNA. Here, reduced bisulfite sequencing is developed for quantitatively sequencing 5fC at single-base resolution. This method is then applied with oxidative bisulfite sequencing to gain a map of 5mC, 5hmC and 5fC in mouse embryonic stem cells. 12 samples, reduced representation bisulphite treatment: 4 replicates each for bisulphite (BS), oxidative BS (oxBS) and reduced BS (redBS) for the detection of 5mC, 5hmC and 5fC. Mouse (strain B6C) embryonic stem cells.
Project description:Active DNA demethylation in mammals involves TET-mediated iterative oxidation of 5-methylcytosine (5mC)/5-hydroxymethylcytosine (5hmC) and subsequent excision repair of highly oxidized cytosine bases 5-formylcytosine (5fC)/5-carboxylcytosine (5caC) by Thymine DNA glycosylase (TDG). However, quantitative and high-resolution analysis of active DNA demethylation activity remains challenging. Here we describe M.SssI methylase-assisted bisulfite sequencing (MAB-seq), a method that directly maps 5fC/5caC at single-base resolution. Genome-wide MAB-seq allows systematic identification of 5fC/5caC in Tdg-depleted embryonic stem cells, thereby generating a base-resolution map of active DNA demethylome. A comparison of 5fC/5caC and 5hmC distribution maps indicates that catalytic processivity of TET enzymes correlates with local chromatin accessibility. MAB-seq also reveals strong strand asymmetry of active demethylation within palindromic CpGs. Integrating MAB-seq with other base-resolution mapping methods enables quantitative measurement of cytosine modification states at key transitioning steps of active demethylation pathway, and reveals a regulatory role of 5fC/5caC excision repair in active DNA demethylation cascade.