Project description:Mapping 6mA at single-base resolution across multiple eukaryotic genomes reveals its genomic distribution patterns, indicating a function in transcriptional regulation.
Project description:N6-methyladenine (6mA) is a natural DNA modification and functions primarily in restriction-modification (R-M) systems in prokaryotes. Recent studies uncovered the existence and revealed the genome-wide distribution of 6mA in eukaryotes. Specifically, it was reported that 6mA was mainly enriched in mammalian mitochondrial DNA (mtDNA) and could regulate mitochondrial activity. we achieved the genome-wide mapping of 6mA in E. coli genome and mammalian mtDNA at single-nucleotide resolution.
Project description:Active regulatory elements in eukaryotes are typically characterized by an open, nucleosome-depleted chromatin structure; mapping areas of open chromatin has accordingly emerged as a widely used tool in the arsenal of modern functional genomics. However, existing approaches for profiling chromatin accessibility are limited by their reliance on DNA fragmentation and short read sequencing, which leaves them unable to provide information about the state of chromatin on larger scales or reveal coordination between the chromatin state of individual distal regulatory elements. To address these limitations, we have developed a method for profiling accessibility of individual chromatin fibers at multi-kilobase length scale (SMAC-seq, or Single-Molecule long-read Acessible Chromatin mapping sequencing assay), enabling the simultaneous, high-resolution, single-molecule assessment of the chromatin state of distal genomic elements. Our strategy is based on combining the preferential methylation of open chromatin regions by DNA methyltransferases (CpG and GpC 5-methylcytosine (5mC) and N6-methyladenosine (m6A) enzymes) and the ability of long-read single-molecule nanopore sequencing to directly read out the methylation state of individual DNA bases. Applying SMAC-seq to the budding yeast Saccharomyces cerevisiae, we demonstrate that aggregate SMAC-seq signals match bulk-level accessibility measurements, observe single-molecule protection footprints of nucleosomes and transcription factors, and quantify the correlation between the chromatin states of distal genomic elements
Project description:To interrogate single-base resolution 6mA sites in the genome-wide, we develop DA-6mA-seq (DpnI-Assisted N6-methylAdenine sequencing), an optimized sequencing method taking advantage of restriction enzyme DpnI, which exclusively cleaves methylated adenine sites. We find DpnI also recognizes other sequence motifs besides the canonical GATC restriction sites, largely expanding the application range of this method. DA-6mA-seq requires less starting material and lower sequencing depth than previous methods, but achieves higher sensitivity, providing a good strategy to identify 6mA in large genome with a low abundance of 6mA. We rebuild the 6mA maps of Chlamydomonas by DA-6mA-seq and then apply this method to another two eukaryotic organisms, Plasmodium and Penicillium. Further analysis reveals most 6mA sites are symmetric at various sequence contexts, suggesting 6mA may function as a new heritable epigenetic mark in eukaryotes. A new sequencing method is developed to detect 6mA in eukaryotes
Project description:In human cells, 5-methylcytosine (5mC) DNA modification plays an important role in gene regulation. However, N6-methyladenine (6mA) DNA modification, which is predominantly present in prokaryotes, is considered to be absent in human genomic DNA. Here, using single molecule real-time (SMRT) sequencing on human blood, we show that DNA 6mA modification is extensively present in human genome, accounting for ~0.051% of the total adenines. [G/C]AGG[C/T] was the most significant motif associated with 6mA modification. 6mA sites are enriched in the exon coding regions and are associated with transcriptional activation. DNA N6-methyladenine and N6-demethyladenine modification in human are mediated by methyltransferase N6AMT1 and demethylase ALKBH1, respectively. The 6mA abundance is significantly lower in cancer tissues compared to adjacent normal tissues, which is accompanied with decreased N6AMT1 and increased ALKBH1 levels. Decrease of 6mA modification level stimulated tumorigenesis in human. Collectively, our results demonstrate that 6mA DNA modification is present in human tissues, and we describe a potential role of the N6AMT1/ALKBH1-6mA regulatory axis in the progression of human cancer.
Project description:The detection of low-abundance DNA N6-methyladenine (DNA-m6A) remains challenging, limiting our understanding of this novel base in eukaryotes. To address this, we introduce an approach for systematically validating the selectivity and sensitivity of antibody-based DNA-m6A methods, revealing most commercial antibodies as poorly selective towards DNA-m6A. Finally, we validate selective anti-DNA-m6A antibodies with sensitivity <2 ppm, and expose distinct pathways mediating endogenous DNA-m6A in C. reinhardtii, A. thaliana, and D. melanogaster.