03 Fakultät Chemie

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Author: search.filters.author.Adam, SabrinaSubject: search.filters.subject.570

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    Methylation of recombinant mononucleosomes by DNMT3A demonstrates efficient linker DNA methylation and a role of H3K36me3
    (2022) Bröhm, Alexander; Schoch, Tabea; Dukatz, Michael; Graf, Nora; Dorscht, Franziska; Mantai, Evelin; Adam, Sabrina; Bashtrykov, Pavel; Jeltsch, Albert
    Recently, the structure of the DNMT3A2/3B3 heterotetramer complex bound to a mononucleosome was reported. Here, we investigate DNA methylation of recombinant unmodified, H3KC4me3 and H3KC36me3 containing mononucleosomes by DNMT3A2, DNMT3A catalytic domain (DNMT3AC) and the DNMT3AC/3B3C complex. We show strong protection of the nucleosomal bound DNA against methylation, but efficient linker-DNA methylation next to the nucleosome core. High and low methylation levels of two specific CpG sites next to the nucleosome core agree well with details of the DNMT3A2/3B3-nucleosome structure. Linker DNA methylation next to the nucleosome is increased in the absence of H3K4me3, likely caused by binding of the H3-tail to the ADD domain leading to relief of autoinhibition. Our data demonstrate a strong stimulatory effect of H3K36me3 on linker DNA methylation, which is independent of the DNMT3A-PWWP domain. This observation reveals a direct functional role of H3K36me3 on the stimulation of DNA methylation, which could be explained by hindering the interaction of the H3-tail and the linker DNA. We propose an evolutionary model in which the direct stimulatory effect of H3K36me3 on DNA methylation preceded its signaling function, which could explain the evolutionary origin of the widely distributed “active gene body-H3K36me3-DNA methylation” connection.
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    Genome-wide deposition of 6-methyladenine in human DNA reduces the viability of HEK293 cells and directly influences gene expression
    (2023) Broche, Julian; Köhler, Anja R.; Kühnel, Fiona; Osteresch, Bernd; Chandrasekaran, Thyagarajan T.; Adam, Sabrina; Brockmeyer, Jens; Jeltsch, Albert
    While cytosine-C5 methylation of DNA is an essential regulatory system in higher eukaryotes, the presence and relevance of 6-methyladenine (m6dA) in human cells is controversial. To study the role of m6dA in human DNA, we introduced it in human cells at a genome-wide scale at GANTC and GATC sites by expression of bacterial DNA methyltransferases and observed concomitant reductions in cell viability, in particular after global GANTC methylation. We identified several genes that are directly regulated by m6dA in a GANTC context. Upregulated genes showed m6dA-dependent reduction of H3K27me3 suggesting that the PRC2 complex is inhibited by m6dA. Genes downregulated by m6dA showed enrichment of JUN family transcription factor binding sites. JUN binds m6dA containing DNA with reduced affinity suggesting that m6dA can reduce the recruitment of JUN transcription factors to target genes. Our study documents that global introduction of m6dA in human DNA has physiological effects. Furthermore, we identified a set of target genes which are directly regulated by m6dA in human cells, and we defined two molecular pathways with opposing effects by which artificially introduced m6dA in GANTC motifs can directly control gene expression and phenotypes of human cells.