ABSTRACT: In this study, we provided the first genome-wide, base pair-resolution map of 6mA in Tetrahymena by applying single-molecule real-time (SMRT) sequencing.
Project description:6mA-DNA-IP-Seq and sequencing of Arabidopsis. Our DeepM6A model was trained on the 6mA sites indentified by the single-molecule real-time (SMRT) sequencing. To validate the robustness of the DeepM6A model, we applied an independent DNA-6mA-IP for A. thaliana, and predicted scores of peaks by using the trained DeepM6A model.
Project description:In mammalian cells, DNA methylation on the 5th position of cytosine (5mC) plays an important role as an epigenetic mark. However, DNA methylation was considered to be absent in C. elegans because of the lack of detectable 5mC as well as homologs of the cytosine DNA methyltransferases. Here, using multiple approaches, we demonstrate the presence of adenine N6-methylation (6mA) in C. elegans DNA. We further demonstrate that this modification increases trans-generationally in a paradigm of epigenetic inheritance. Importantly, we identify a DNA demethylase, NMAD-1, and a potential DNA methyltransferase, DAMT-1, which regulate 6mA levels and crosstalk between methylation of histone H3K4me2 and 6mA, and control the epigenetic inheritance of phenotypes associated with the loss of the H3K4me2 demethylase spr-5. Together, these data identify a novel DNA modification in C. elegans and raise the exciting possibility that 6mA may be a carrier of heritable epigenetic information in eukaryotes. SMRT-sequencing for a mixed cell population of wildtype worms 6mA ChIP-Seq for a mixed cell population of wildtype worms
Project description:N6-methyldeoxyadenosine (6mA or m6dA) was shown more than 40 years ago to exist in simple eukaryotes, yet functional studies have been limited. Recent investigations in multiple eukaryotes suggest 6mA as a potential DNA epigenetic mark that plays regulatory roles in gene regulation. Here we use Tetrahymena thermophila as a model to examine the effects of 6mA on nucleosome positioning. We have employed independent methods to identify genome-wide 6mA distribution, which revealed the enrichment after transcription start sites with a periodic pattern and a mutually exclusive relationship with the positions of nucleosomes. The exclusive distribution pattern of 6mA and nucleosome can be recapitulated by in vitro nucleosome assembly on native Tetrahymena genomic DNA, but not on DNA without 6mA. Model DNA containing artificially installed 6mA resists nucleosome assembling compared to unmodified DNA in vitro. Computational simulation revealed that 6mA increases dsDNA rigidity, which disfavors nucleosome wrapping. Knockout of a potential 6mA methyltransferase disturbs the nucleosome positioning in Tetrahymena, leading to the transcriptome-wide change of gene expression. These findings uncover a new mechanism by which DNA 6mA assists to shape the chromatin topology in order to stabilize gene expression.
Project description:DNA methylation on N6-adenine (6mA), the most prevalent DNA modification in prokaryotes, has recently been found as a potentially new epigenetic mark in several unicellular and multicellular eukaryotes. However, the distribution patterns and potential functions of 6mA in land plants, which are primary producers for most ecosystems, remain completely unknown. Here we report global profiling of 6mA sites at single-nucleotide resolution in the genomes of Arabidopsis thaliana Columbia-0 (Col), using single-molecule real-time sequencing. DNA methylome analysis shows that 6mA sites are widely distributed across the Col genomes and enriched over the pericentromeric heterochromatin regions. Nearly 30% of 6mA sites are present in gene bodies with a trend of enrichment around the transcriptional start site. In addition to a common consensus 6mA site found in other eukaryotes, novel 6mA sites were found, indicating that 6mA could evolve new functions in land plants. Further analysis of 6mA methylome and RNA-sequencing data demonstrates that 6mA positively correlates with the gene expression level in Col plants. Consistently, DNA affinity chromatography coupled with mass spectrometry reveals that histone variants associated with actively expressed genes interact with 6mA DNA. Our results uncover 6mA as a DNA mark associated with actively expressed genes in Arabidopsis, indicating that 6mA could serve as a potentially novel epigenetic mark in land plants.
Project description:DNA methylation on N6-adenine (6mA), the most prevalent DNA modification in prokaryotes, has recently been found as a potentially new epigenetic mark in several unicellular and multicellular eukaryotes. However, the distribution patterns and potential functions of 6mA in land plants, which are primary producers for most ecosystems, remain completely unknown. Here we report global profiling of 6mA sites at single-nucleotide resolution in the genomes of Arabidopsis thaliana Columbia-0 (Col), using single-molecule real-time sequencing. DNA methylome analysis shows that 6mA sites are widely distributed across the Col genomes and enriched over the pericentromeric heterochromatin regions. Nearly 30% of 6mA sites are present in gene bodies with a trend of enrichment around the transcriptional start site. In addition to a common consensus 6mA site found in other eukaryotes, novel 6mA sites were found, indicating that 6mA could evolve new functions in land plants. Further analysis of 6mA methylome and RNA-sequencing data demonstrates that 6mA positively correlates with the gene expression level in Col plants. Consistently, DNA affinity chromatography coupled with mass spectrometry reveals that histone variants associated with actively expressed genes interact with 6mA DNA. Our results uncover 6mA as a DNA mark associated with actively expressed genes in Arabidopsis, indicating that 6mA could serve as a potentially novel epigenetic mark in land plants.
Project description:DNA methylation on N6-adenine (6mA) has recently been found as a potentially new epigenetic mark in several unicellular and multicellular eukaryotes. However, its distribution patterns and potential functions in land plants, which are primary producers for most ecosystems, remain completely unknown. Here we report global profiling of 6mA sites at single-nucleotide resolution in the genome of Arabidopsis thaliana using single-molecule real-time sequencing. 6mA sites are widely distributed across the Arabidopsis genome and enriched over the pericentromeric heterochromatin regions. Nearly 30% of 6mA sites are present in gene bodies. Further analysis of 6mA methylome and RNA-sequencing data demonstrates that 6mA frequency positively correlates with the gene expression level in Arabidopsis. Consistently, histone variants associated with actively expressed genes interact with 6mA DNA. Our results uncover 6mA as a DNA mark associated with actively expressed genes in Arabidopsis, suggesting that 6mA serves as a novel epigenetic mark in land plants.
Project description:DNA methylation on N6-adenine (6mA) has recently been found as a potentially new epigenetic mark in several unicellular and multicellular eukaryotes. However, its distribution patterns and potential functions in land plants, which are primary producers for most ecosystems, remain completely unknown. Here we report global profiling of 6mA sites at single-nucleotide resolution in the genome of Arabidopsis thaliana using single-molecule real-time sequencing. 6mA sites are widely distributed across the Arabidopsis genome and enriched over the pericentromeric heterochromatin regions. Nearly 30% of 6mA sites are present in gene bodies. Further analysis of 6mA methylome and RNA-sequencing data demonstrates that 6mA frequency positively correlates with the gene expression level in Arabidopsis. Consistently, histone variants associated with actively expressed genes interact with 6mA DNA. Our results uncover 6mA as a DNA mark associated with actively expressed genes in Arabidopsis, suggesting that 6mA serves as a novel epigenetic mark in land plants.
Project description:We report the application of 6mA IP-sequencing technology for high-throughput profiling in rice tissues of 12 days' leaf. By obtaining over 20 million high quality clean mapping sequenced reads from immunoprecipitated DNA, we generate genome-wide 6mA maps of rice 12 days' leaf. Using mass spectrometry and immunoprecipitation and validation with analysis of single-molecule real-time sequencing, we observed that about 0.2% of all adenines are 6mA-methylated in the rice genome. 6mA occurs most frequently at GAGG motifs and is mapped to about 20% of genes and 14% of transposable elements (TEs). In promoters, 6mA marks silent genes, but in bodies correlates with gene activity. 6mA overlaps with 5-methylated cytosine (5mC) at CG sites in gene bodies and is complementary to 5mC at CHH sites in TEs. We show that OsALKBH1 may be potentially involved in 6mA demethylation in rice. The results suggest that 6mA is complementary to 5mC as an epigenomic mark in rice and reinforces a distinct role for 6mA as a gene-expression associated epigenomic mark in eukaryotes.
Project description:While DNA N6-methyl-deoxyadenosine (6mA) is abundant in bacteria and protists, its presence and function in mammalian genomes have been less clear. We present Direct-Read 6mA sequencing (DR-6mA-seq), an antibody-independent method to measure 6mA at base-resolution with high sensitivity. DR-6mA-seq employs a unique mutation-based strategy to reveal 6mA sites as misincorporation signatures without any chemical or enzymatic modulation of 6mA. We validated DR-6mA-seq through successful mapping of the well-characterized G(6mA)TC motif in the E. coli DNA and identified 6mA sites in the mammalian mitochondrial DNA. As expected, when applying DR-6mA-seq to mammalian systems, we found that genomic DNA (gDNA) 6mA abundance is in general low in most mammalian tissues and cells; however, we did observe distinct gDNA 6mA sites in mouse testis and glioblastoma cells. DR-6mA-seq provides an enabling tool to detect 6mA at single-base resolution with high sensitivity for a comprehensive understanding of DNA 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.