Project description:Functional characterization of the transcriptome requires tools for the systematic investigation of RNA post-transcriptional modifications. 2’-O-Methylation of the ribose moiety is one of the most abundant post-transcriptional modifications of the RNA. We describe here a high-throughput method that enables fast and accurate mapping at single-base resolution, and quantitation, of 2’-OMe modified residues. Our approach expands the actual repertoire of methods for transcriptome-wide mapping of RNA post-transcriptional modifications.
Project description:Single-base resolution DNA methylomes have been accomplished for both Arabidopsis and human cells which have high genome methylation levels by Illumina ultra-high-throughput bisulfite sequencing technology (MethylC-Seq). Here by combining MethylC-Seq and biological replicate strategies we generated single-base resolution methylome for the silkworm which has low genome methylation levels like other insects. Our conservative estimation showed that methylcytosines (mCs) accout for about 0.11% of genomic cytosines, exclusively in CG context. The CG methylation is significantly enriched in gene bodies and positively correlated with gene expression levels, suggesting its positive role in gene transcription in silkworms. However, the well-documented functions of methylation on promoters and rDNAs in plants and mammals do not seem to have effects in insects. Methylated genes are enriched in functions involved in cellular metabolism and biosynthesis. Small RNA (smRNA) loci are also significantly enriched in gene bodies, and moreover, the smRNA loci and the predicted target sites of microRNA have high level of CG methylation, indicating functional involvement of smRNAs in the genic methylation This first methylome for silkworms provides a foundation for further studies on the epigenetic gene regulation of silkworms’ or even insects’ gene methylation. Each silk gland of 5th instar larvae of two individuals (called Biological Replicate 1 and 2, respectively) of the silkworm (Bombyx mori) strain Dazao was ground into powder in liquid nitrogen. Half of the powder from each silk gland was used to extract total DNAs using DNeasy Blood & Tissue Kit (Qiagen) and another half was used to extract total RNAs using RNeasy Mini Kit (Qiagen). We sequenced bisulfite-treated total DNA extracted from the silk glands of the two individuals, using Illumina Ultra-High-Throughput Sequencing, generating the Single-Base Resolution Methylomes. To reveal functional consequences of gene body methylation, we generated expression profiles for the two individuals’ silk glands using Digital Gene Expression tag profiling (DGE) technology, which combines classic SAGE (Serial Analysis of Gene Expression) and Illumina ultra-high-throughput sequencing technology.
Project description:In this study, we aim to generate genome-scale DNA methylation profiles at single-base resolution in different rice cultivars (IR64, Nagina 22 and Pokkali) under control and stress conditions. Using high-throughput whole genome bisulfite Sequencing, we generated DNA methylation maps covering the vast majority of cytosines in the rice genome. More than 152 million high quality reads were obtained for each tissue sample using Illumina platform. We discovered extensive DNA methylation in rice cultivars, identified the context and level of methylation at each site.Numerous differentially methylated regions (DMRs) among different cultivars under control and stress conditions were identified and many of them were associated with differential gene expression. The high resolution methylome maps of different rice genotypes and differentially methylated regions will serve as reference for understanding the epigenetic regulation of stress responses in plants. Whole genome bisulfite sequencing of seven control/stressed samples from three rice cultivars (IR64, N22 and Pokkali)
Project description:The parasitoid wasp Nasonia vitripennis is an emerging genetic model for functional analysis of DNA methylation. Here, we characterize genome-wide methylation at a base-pair resolution, and compare these results to gene expression across five developmental stages and to methylation patterns reported in other insects. An accurate assessment of DNA methylation across the genome is accomplished using bisulfite sequencing of adult females from a highly inbred line. One-third of genes show extensive methylation over the gene body, yet methylated DNA is not found in non-coding regions and rarely in transposons. Methylated genes occur in small clusters across the genome. Methylation demarcates exon-intron boundaries, with elevated levels over exons, primarily in the 5’ regions of genes. It is also elevated near the sites of translational initiation and termination, with reduced levels in 5’ and 3’ UTRs. Methylated genes have higher median expression levels and lower expression variation across development stages than non-methylated genes. There is no difference in frequency of differential splicing between methylated and non-methylated genes, and as yet no established role for methylation in regulating alternative splicing in Nasonia. Phylogenetic comparisons indicate that many genes maintain methylation status across long evolutionary time scales. Nasonia methylated genes are more likely to be conserved in insects, but even those that are not conserved show broader expression across development than comparable non-methylated genes. Finally, examination of duplicated genes shows that those paralogs that have lost methylation in the Nasonia lineage following gene duplication evolve more rapidly, show decreased median expression levels, and increased specialization in expression across development. Methylation of Nasonia genes signals constitutive transcription across developmental stages, whereas non-methylated genes show more dynamic developmental expression patterns. We speculate that loss of methylation may result in increased developmental specialization in evolution and acquisition of methylation may lead to broader constitutive expression. Whole-genome bisulfite sequencing of 24-hour adult female Nasonia vitripennis whole body samples using Iilumina GAIIx and HiSeq2000.
Project description:Through chemoselective methylthio group bioconjugation, we introduce a new approach (redox activated chemical tagging sequencing, ReACT-seq) to detect ms2i6A transcriptome-wide at single-base resolution.
Project description:N6-methyladenosine (m6A) is the most abundant modified base in eukaryotic mRNA and has been linked to diverse effects on mRNA fate and function. Current m6A mapping approaches rely on immunoprecipitation of m6A-containing RNA fragments to identify regions of transcripts that contain m6A. This approach localizes m6A residues to 100-200 nt-long regions of transcripts. The precise position of m6A in mRNAs cannot be identified on a transcriptome-wide level because there are no chemical methods to distinguish between m6A and adenosine. Here we show that anti-m6A antibodies can induce specific mutational signatures at m6A residues after ultraviolet light-induced antibody-RNA crosslinking and reverse transcription. Similarly, we find these antibodies induce mutational signatures at N6, 2’-O-dimethyladenosine (m6Am), a nucleotide found at the first encoded position of certain mRNAs. Using these mutational signatures, we map m6A and m6Am at single-nucleotide resolution in human and mouse mRNA and identify snoRNAs as a novel class of m6A-containing ncRNAs. UV-crosslinking and immunoprecipitation with m6A-specific antibodies was used to map m6A and m6Am in cellular RNA with single nucleotide resolution.
Project description:We have combined standard micrococcal (MNase) digestion of nuclei with a modified protocol for construction paired-end DNA sequencing libraries to map both nucleosomes and subnucleosome-sized particles at single base-pair resolution throughout the budding yeast genome. We found that partially unwrapped nucleosomes and subnucleosome-sized particles can occupy the same position within a cell population, suggesting dynamic behavior. By varying the time of MNase digestion, we have been able to observe changes that reflect differential sensitivity of particles, including eviction of nucleosomes. Our protocol and mapping method provide a general strategy for characterizing full epigenomes. We used micrococcal nuclease mapping, chromatin immunoprecipitation and paired-end sequencing to determine the structure of yeast centromeres at single base-pair resolution.
Project description:The study of 5-hydroxylmethylcytosines (5hmC), the sixth base of the mammalian genome, as an epigenetic mark has been hampered by a lack of method to map it at single-base resolution. Previous affinity purification-based methods could not precisely locate 5hmC nor accurately determine its relative abundance at each modified site. We here present a genome-wide approach for mapping 5hmC at base resolution. Application of this new method to the embryonic stem cells not only confirms widespread distribution of 5hmC in mammalian genome, but also reveals a strong sequence bias and strand asymmetry at sites of 5hmC. Additionally, the relative abundance of 5hmC varies significantly depending on the types of functional sequences, suggesting different mechanisms for 5hmC deposition and maintenance. Furthermore, we observe high levels of 5hmC and reciprocally low levels of 5mC at transcription factor binding sites, revealing a dynamic DNA methylation process at cis-regulatory elements. Base resolution sequencing of 5 hydroxymethylcytosine in human and mouse embryonic stem cells