Project description:Nucleosomes compact and regulate access to DNA in the nucleus, and are composed of approximately 147 bases of DNA wrapped around a histone octamer. Here we report a genome-wide nucleosome positioning analysis of Arabidopsis thaliana utilizing massively parallel sequencing of mononucleosomes. By combining this data with profiles of DNA methylation at single base resolution, we identified ten base periodicities in the DNA methylation status of nucleosome-bound DNA and found that nucleosomal DNA was more highly methylated than flanking DNA. These results suggest that nucleosome positioning strongly influences DNA methylation patterning throughout the genome and that DNA methyltransferases preferentially target nucleosome-bound DNA. We also observed similar trends in human nucleosomal DNA suggesting that the relationships between nucleosomes and DNA methyltransferases are conserved. Finally, as has been observed in animals, nucleosomes were highly enriched on exons, and preferentially positioned at intron-exon and exon-intron boundaries. RNA Pol II was also enriched on exons relative to introns, consistent with the hypothesis that nucleosome positioning regulates Pol II processivity. We also found that DNA methylation enriched on exons, consistent with the targeting of DNA methylation to nucleosomes. Genomic DNA from Arabidopsis thaliana was MNase digested, size selected and sequenced. Genomic DNA associated with H3 was isolated using ChIP and sequenced. Genomic DNA from human HSF1 embryonic stem cells was bisulfite converted and sequenced.
Project description:DNA methylation and nucleosome positioning work together to generate chromatin structures that regulate gene expression. Nucleosomes are typically mapped using nuclease digestion requiring significant amounts of material and varying enzyme concentrations. We have developed a method (NOMe-seq) that uses a GpC methyltransferase (M.CviPI) and next generation sequencing to generate a high resolution footprint of nucleosome positioning genome-wide using less than 1 million cells while retaining endogenous DNA methylation information from the same DNA strand. Using a novel bioinformatics pipeline we show a striking anti-correlation between nucleosome occupancy and DNA methylation at CTCF regions, that is not present at promoters. We further show that the extent of nucleosome depletion at promoters is directly correlated to expression level and can accommodate multiple nucleosomes and provide genome-wide evidence that expressed non-CpG island promoters are nucleosome depleted. Importantly, NOMe-seq obtains DNA methylation and nucleosome positioning information from the same DNA molecule, giving the first genome-wide DNA methylation and nucleosome positioning correlation at the single molecule and thus, single cell level that can be used to monitor disease progression and response to therapy. Nucleosome Occupancy and Methylome-Sequencing (NOMe-Seq) on IMR90 cell line and 2 GBM cell lines
Project description:DNA cytosine methylation is a hallmark of epigenetic gene silencing. DNA demethylation requires ROS1, a bifunctional DNA glycosylase/lyases and open chromatin status mediated by IDM1. HDA6 is a RDP3-like histone deacetylase and was confirmed to mediate DNA methylation. In previous screening for ros1 suppressor, we identified two hda6 mutants reverting ros1-caused hypermethylation at RD29A and 35S promoters respectively, indicating the antagonization of DNA methylation between HDA6 and ROS1. To learn antagonized effects between HDA6 and ROS1 at DNA cytosine methylation genome-wide, we performed whole genome bisulfite sequencing to search antagonized targets of HDA6 and ROS1 and their specific targets to evaluate their roles on DNA methylation. To evaluate HDA6’s roles in sRNA biogenesis and nucleosome positioning, we also performed small RNA sequencing and genome-wide mapping of nucleosome positioning of C24, ros1, hda6-9 and hda6-10. Our results indicate that around 43% ros1-caused CG hypermethylation, 74.5% and 84.5% ros1-caused CHG and CHH hypermethylation were reverted by the two hda6 alleles in the ros1 background respectively. These results indicate that most of ROS1-demethylated targets are also HDA6-mediated DNA methylated targets. In addition, we observed that HDA6-affected DNA methylation targets are far more than ROS1-demethylation targets at CHG and CHH context, but not at CG context. sRNA analysis showed that HDA6 inhibits LTR/Gypsy and TE gene 24nt siRNA accumulation, while promotes RC/Helitron 24nt siRNA accumulation. Our Mono-nucleosome positioning data further showed that the two hda6 alleles have striking difference on nucleosome positioning, hda6-10 obviously have different nucleosome positioning patterns with hda6-9. Our results indicate HDA6 not only mediates overall DNA methylation at CG, CHG and CHH context, and antagonizes with ROS1 mediated DNA demethylation, but also regulates nucleosome positioning and small RNA accumulation at some genome specific regions.
Project description:Nucleosomes compact and regulate access to DNA in the nucleus, and are composed of approximately 147 bases of DNA wrapped around a histone octamer1, 2. Here we report a genome-wide nucleosome positioning analysis of Arabidopsis thaliana utilizing massively parallel sequencing of mononucleosomes. By combining this data with profiles of DNA methylation at single base resolution, we identified ten base periodicities in the DNA methylation status of nucleosome-bound DNA and found that nucleosomal DNA was more highly methylated than flanking DNA. These results suggest that nucleosome positioning strongly influences DNA methylation patterning throughout the genome and that DNA methyltransferases preferentially target nucleosome-bound DNA. We also observed similar trends in human nucleosomal DNA suggesting that the relationships between nucleosomes and DNA methyltransferases are conserved. Finally, as has been observed in animals, nucleosomes were highly enriched on exons, and preferentially positioned at intron-exon and exon-intron boundaries. RNA Pol II was also enriched on exons relative to introns, consistent with the hypothesis that nucleosome positioning regulates Pol II processivity. We also found that DNA methylation enriched on exons, consistent with the targeting of DNA methylation to nucleosomes.
Project description:Nucleosomes compact and regulate access to DNA in the nucleus, and are composed of approximately 147 bases of DNA wrapped around a histone octamer1, 2. Here we report a genome-wide nucleosome positioning analysis of Arabidopsis thaliana utilizing massively parallel sequencing of mononucleosomes. By combining this data with profiles of DNA methylation at single base resolution, we identified ten base periodicities in the DNA methylation status of nucleosome-bound DNA and found that nucleosomal DNA was more highly methylated than flanking DNA. These results suggest that nucleosome positioning strongly influences DNA methylation patterning throughout the genome and that DNA methyltransferases preferentially target nucleosome-bound DNA. We also observed similar trends in human nucleosomal DNA suggesting that the relationships between nucleosomes and DNA methyltransferases are conserved. Finally, as has been observed in animals, nucleosomes were highly enriched on exons, and preferentially positioned at intron-exon and exon-intron boundaries. RNA Pol II was also enriched on exons relative to introns, consistent with the hypothesis that nucleosome positioning regulates Pol II processivity. We also found that DNA methylation enriched on exons, consistent with the targeting of DNA methylation to nucleosomes. Genomic DNA associated with RNAP II was isolated by ChIP using an anti-PolII antibody.