Identification of Multiple Proteins Coupling Transcriptional Regulation to Genome Stability in Arabidopsis thaliana
ABSTRACT: Eukaryotic genomes are heavily regulated by epigenetic marks that often act to modulate the transcriptional control of genetic elements. In Arabidopsis thaliana the ATXR5 and ATXR6 histone methyltransferases, and their cognate H3K27 monomethylation mark, act in transcriptional silencing while also maintaining genome stability by preventing generation of excess DNA corresponding to pericentromeric heterochromatin. In this study we characterize the atxr5 atxr6 transcriptome and its relationship to the DNA damage response which suggests that the atxr5 atxr6 transcriptional defects may be epistatic to the genome instability defects in the mutants. In addition we isolate several factors that modulate both the transcriptional and genomic instability phenotypes of atxr5 atxr6 mutants, which suggest a mechanism for atxr5 atxr6-induced extra DNA involving conflicts between the replicative and transcriptional processes in the cell. PolyA RNA sequencing (RNA-seq), whole-genome resequencing (DNA-seq), and whole-genome bisulfite sequencing (methyl-seq) was performed on Arabidospsis thaliana mutant and wildtype plants. DNA-seq was used to characterize DNA copy number and map EMS-induced mutations, RNA-seq was used to quantify transcript abundance and map EMS-induced mutations, and methyl-seq was used to assess DNA methylation. Details of the relationship between samples in this series and figures in the associated manuscript can be found in Supplemental Table 4 of the associated manuscript. Unless otherwise noted in the description all lines are ecotype Columbia, and all genotypes should be assumed homozygous unless otherwise indicated with a '/'.
Project description:DNA methylation is a conserved epigenetic gene regulation mechanism. DOMAINS REARRANGED METHYLTRANSFERASE (DRM) is a key de novo methyltransferase in plants, but how DRM acts mechanistically is poorly understood. Here, we report the crystal structure of the methyltransferase domain of tobacco DRM (NtDRM) and reveal a molecular basis for its rearranged structure. NtDRM forms a functional homo-dimer critical for catalytic activity. We also show that Arabidopsis DRM2 exists in complex with the siRNA effector ARGONAUTE4 (AGO4) and preferentially methylates one DNA strand, likely the strand acting as the template for non-coding Pol V RNA transcripts. This strand-biased DNA methylation is also positively correlated with strand-biased siRNA accumulation. These data suggest a model in which DRM2 is guided to target loci by AGO4-siRNA and involves base-pairing of associated siRNAs with nascent RNA transcripts. Whole-genome bisulfite sequencing was done for a wildtype line (ecotype Col) as well as various transgenic lines in a drm2 mutant background (ecotype Col). Each transgenic line expressed a version of the DRM2 protein that was either wildtype or carried induced mutations in order to test the function of various domains in the DRM2 protein. Two sets of whole-genome bisulfite were performed (130615 or 131216) and comparisons were mainly done within sets although comparisons can also be done between sets. The drm2 mutant methylome was also analyzed in this study using a previously published whole-genome bisulfite library (GSE39901).
Project description:Whole genome bisulfite sequencing was performed on Chromomethylase-2 and Dicer-like-3 knockout mutants in order to confirm the results from genome wide association mapping and to identify the respective genomic regions that they target. Bisulfite sequencing of knockout mutants and WT controls
Project description:Here we investigate DNA methylation variation in Swedish Arabidopsis thaliana accessions, demonstrating that methylation of transposable elements is temperature sensitive and associated with genetic polymorphism in both cis and trans, whereas gene body methylation is highly correlated with climate of origin and associated with genetic polymorphism in trans that shows evidence of local adaptation. While genome-wide surveys of naturally occurring DNA methylation have been published previously, the degree of genetic control revealed here is unprecedented. Furthermore, the observation that DNA methylation is associated with climate, and is apparently adaptively important, is completely novel. Bisulfite sequencing of 152 Swedish Arabidobsis accessions grown at 10 C and 121 grown at 16 C
Project description:In Arabidopsis, CHG DNA methylation is controlled by the H3K9 methylation mark through a self-reinforcing loop between DNA methyltransferase CHROMOMETHYLASE3 (CMT3) and H3K9 histone methyltransferase KRYPTONITE/SUVH4 (KYP). We report on the structure of KYP in complex with methylated DNA, substrate H3 peptide and cofactor SAH, thereby defining the spatial positioning of the SRA domain relative to the SET domain. The methylated DNA is bound by the SRA domain with the 5mC flipped out of the DNA, while the H3(1-15) peptide substrate binds between the SET and post-SET domains, with the epsilon-ammonium of K9 positioned adjacent to bound SAH. These structural insights complemented by in vivo functional data on key mutants of residues lining the 5mC and H3K9-binding pockets within KYP, establish how methylated DNA recruits KYP to the histone substrate. Together, the structures of KYP and previously reported CMT3 complexes provide insights into molecular mechanisms linking DNA and histone methylation. Plants homozygous for null mutations in the KRYPTONITE H3K9 methyltransferase were stably transformed with transgenes encoding the wildtype KYP protein or transgenes carrying induced point mutations in the KYP active site. The resulting lines were assayed for DNA methylation by whole-genome bisulfite sequencing to learn the efficiency with which wildtype and mutant versions of the KYP protein could restore DNA methylation lost in a kyp mutant. Samples 7 and 8 were run as single Illumina lanes and as such were compared to a previous Col sample (GSM881756), this Col sample was realigned to the TAIR10 genome for this study and as such updated processed files are available with this submission. These samples were used to define kyp mutant CHG context DMRs that were complemented upon introduction of the wildtype KYP protein. Samples 1-6 were run as multiplexed samples and were used to assay the degree of complementation for various point mutants. All plants are in the Col ecotype background.
Project description:The earliest stages of Huntington’s disease are marked by changes in gene expression that are caused in an indirect and poorly understood manner by polyglutamine expansions in the huntingtin protein (HTT). To explore the hypothesis DNA methylation may be altered in cells expressing mutated HTT, we use reduced-representation bisulfite sequencing (RRBS) to map sites of DNA methylation in cells carrying either wild-type or mutant HTT. We find that a large fraction of the genes that change in expression in the presence of mutant huntingtin demonstrate significant changes in DNA methylation. Regions with low CpG content, which have previously been shown to undergo methylation changes in response to neuronal activity, are disproportionately affected. Based on the sequence of regions that change in methylation, we identify AP-1 and SOX2 as transcriptional regulators associated with DNA methylation changes, and we confirm these hypotheses using genome-wide chromatin immunoprecipitation (ChIP-Seq). Our findings suggest new mechanisms for the effects of polyglutamine-expanded HTT. These results also raise important questions about the potential effects of changes in DNA methylation on neurogenesis and at later stages, cognitive decline in Huntington’s patients. RRBS in STHdhQ7/Q7 and STHdhQ111/Q111 cells
Project description:Intrauterine growth restriction (IUGR) is one of the most common adverse pregnancy outcomes with high risk of perinatal morbidity and mortality, and affects up to 7% of pregnancies. Here, seven pairs of placentas were employed for whole genomic promoter DNA methylation profiling and some of the candidate differentially methylated promoters were further validated in additional twelve pairs of samples. Consistent with previous report, our results further indicated that IUGR associated placentas harbored a distinct promoter DNA hypomethylation pattern and the result was further confirmed byultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) In this study, seven pairs of MC twins that were diagnosed as severely growth-discordant (one twin with IUGR but another one was normal) were enrolled for DNA methylation identification.Promoters are defined as the regions crossing the upstream 2200bp and downstream 500bp of the transcriptional start site. A complete set of 34163 genes located in the 22 autosomes and the XY sex chromosomes were prepared based on the RefSeq gene files (http://genome.ucsc.edu/, hg19). The promoters overlapped with each other were merged to form a large region, resulting in 20882 merged candidate regions ranging from 2700bp to 8864bp. The capture probes were designed and synthesized by Roche Nimblegen Incorporation, consisted of 150,407 oligonucleotides.
Project description:Patterns of DNA methylation are established during gametogenesis. The catalytically-inactive adaptor Dnmt3L is crucial to ensure this occurs correctly. In vitro, Dnmt3L binds to the N terminal tail of histone H3 but the function of this interaction during development is unknown. Here we show that Dnmt3L-histone H3 interaction is necessary for spermatogenesis. Mutant animals exhibit reduced fertility, defective methylation establishment at retrotransposons coupled with their reactivation and meiotic catastrophe. The spermatogonial stem cell pool is also defective, with mutant cells displaying marked changes in gene expression. Genome-wide methylation analysis reveals reductions in CG methylation as well as severe loss of non-CG methylation suggesting that non-CG methylation is specifically sensitive to the ability of Dnmt3L to bind histone H3. MethylC-Seq of wild-type and Dnmt3LA/A 1dpp prospermatagonia
Project description:Bisulfite padlock probe technique was used to examine DNA modifications at the lactase gene region for human and mouse tissues DNA modifications were investigated in human sperm, blood, jejunal enterocytes and jejunum lacking enterocytes, as well as mouse jejunal enterocytes and jejunum lacking enterocytes. For WGA samples, a genome devoid of DNA modifications was used to verify the efficiency of the bisulfite conversion reactions (the tissue sources were human or mouse intestine).
Project description:Peanut (Arachis hypogaea) has a large (~2.7 Gbp) allotetraploid genome with closely related component genomes making its genome very challenging to assemble. Here we report genome sequences of its diploid ancestors (A. duranensis and A. ipaënsis). We show they are similar to the peanut’s A- and B-genomes and use them use them to identify candidate disease resistance genes, create improved tetraploid transcript assemblies, and show genetic exchange between peanut’s component genomes. Based on remarkably high DNA identity and biogeography, we conclude that A. ipaënsis may be a descendant of the very same population that contributed the B-genome to cultivated peanut. Whole Genome Bisulphite Sequencing of the peanut species Arachis duranensis and Arachis ipaensis.
Project description:We report the analysis of DNA methylation in mouse chromaffin cell lines using reduced representation bisulfite sequencing (RRBS). We compared DNA methylation profiles of cell lines with or without a knock-out of Sdhb gene, showing that Sdhb disruption results in a hypermethylator phenotype. Reduced representation bisulfite sequencing of 4 mouse chromaffin cell samples (2 Sdhb wild-type and 2 Sdhb knock-out).