Project description:DNA methylation is a central epigenetic modification that has essential roles in cellular processes including chromatin structure, gene regulation, development and disease. The de novo DNA methyltransferases are responsible for the generation of genomic methylation patterns, but the underlying mechanisms are still poorly understood. Here, we show that phosphorylation of DNMT3A by the CK2 protein kinase regulates the establishment of DNA methylation patterns. We find that DNMT3A is phosphorylated by CK2 at two key residues located near its PWWP domain. We observed that, through phosphorylation of these residues, CK2 negatively regulates DNMT3AM-bM-^@M-^Ys ability to methylate DNA and consistent with this, CK2 was found to decrease overall genomic level of 5-methylcytosine. Further, genome-wide DNA methylation analysis in CK2-depleted cells revealed that CK2 affects primarily CpG methylation of several heterochromatin repeats as well as Alu elements. Along these lines, we found that CK2-mediated phosphorylation of DNMT3A was required for its proper heterochromatin localization. Our results define phosphorylation as a new mode of regulation of de novo DNA methyltransferase function. These findings further uncover a previously unrecognized mechanism for the regulation of methylation at repetitive elements. They shed new light into the origin of DNA methylation patterns. Bisulphite converted DNA from 6 samples were hybridised to the Illumina Infinium 27K Human Methylation Beadchip v1.2
Project description:DNA methylation is a central epigenetic modification that has essential roles in cellular processes including chromatin structure, gene regulation, development and disease. The de novo DNA methyltransferases are responsible for the generation of genomic methylation patterns, but the underlying mechanisms are still poorly understood. Here, we show that phosphorylation of DNMT3A by the CK2 protein kinase regulates the establishment of DNA methylation patterns. We find that DNMT3A is phosphorylated by CK2 at two key residues located near its PWWP domain. We observed that, through phosphorylation of these residues, CK2 negatively regulates DNMT3A’s ability to methylate DNA and consistent with this, CK2 was found to decrease overall genomic level of 5-methylcytosine. Further, genome-wide DNA methylation analysis in CK2-depleted cells revealed that CK2 affects primarily CpG methylation of several heterochromatin repeats as well as Alu elements. Along these lines, we found that CK2-mediated phosphorylation of DNMT3A was required for its proper heterochromatin localization. Our results define phosphorylation as a new mode of regulation of de novo DNA methyltransferase function. These findings further uncover a previously unrecognized mechanism for the regulation of methylation at repetitive elements. They shed new light into the origin of DNA methylation patterns.
Project description:DNA methylation is a central epigenetic modification that has essential roles in cellular processes including chromatin structure, gene regulation, development and disease. The de novo DNA methyltransferases are responsible for the generation of genomic methylation patterns, but the underlying mechanisms are still poorly understood. Here, we show that phosphorylation of DNMT3A by the CK2 protein kinase regulates the establishment of DNA methylation patterns. We find that DNMT3A is phosphorylated by CK2 at two key residues located near its PWWP domain. We observed that, through phosphorylation of these residues, CK2 negatively regulates DNMT3A’s ability to methylate DNA and consistent with this, CK2 was found to decrease overall genomic level of 5-methylcytosine. Further, genome-wide DNA methylation analysis in CK2-depleted cells revealed that CK2 affects primarily CpG methylation of several heterochromatin repeats as well as Alu elements. Along these lines, we found that CK2-mediated phosphorylation of DNMT3A was required for its proper heterochromatin localization. Our results define phosphorylation as a new mode of regulation of de novo DNA methyltransferase function. These findings further uncover a previously unrecognized mechanism for the regulation of methylation at repetitive elements. They shed new light into the origin of DNA methylation patterns.
Project description:DNA methylation is a key epigenetic modification regulating genome organization, stability, and gene expression. Stable DNA methylation critically relies on methyl groups provided through folate-mediated one-carbon (C1) metabolism, yet the origin and regulation of C1 supply remain elusive. Here we demonstrate that photorespiration serves as a major C1 source for DNA methylation in Arabidopsis. We show that C1 from formate, a photorespiratory byproduct, is incorporated into 5-methyl-cytosine via the reductive cytosolic folate pathway. This occurs predominantly during the day, negatively regulating serine utilization as alternative C1 source. Consequently, suppression of photorespiration under elevated CO₂ levels alters the DNA methylation landscape, an effect exacerbated when regulation of C1 metabolism by the formate-dependent pathway is impaired. Thus, our findings link the fundamental metabolic process of photorespiration to epigenetic stability, highlighting how rising atmospheric CO₂ levels can induce DNA methylation changes.
Project description:The DNA methylation program is at the bottom layer of the epigenetic regulatory cascade of vertebrate development. While the methylation at C-5 position of the cytosine (C) residues on the vertebrate genomes is achieved through the catalytic activities of the DNA methyltransferases (DNMTs), the conversion of the methylated cytosine (5mC) could be accomplished by the combined actions of the TET enzyme and DNA repair. Interestingly, it has been found recently that the mouse and human DNMTs also possess active DNA demethylation activity in vitro in a Ca2+- and redox condition-dependent manner. We report here the study of tracking down the fate of the methyl group removed from 5mC on DNA during in vitro demethylation reaction by mouse de novo DNMTs, i.e. DNMT3A and DNMT3B. Remarkably, the methyl group becomes covalently linked to the catalytic cysteines utilized by the two de novo DNMTs in their DNA methylation reactions. Thus, the forward and reverse reactions of DNA methylations by the DNMTs may utilize the same cysteine residue(s) as the active site despite of their distinctive pathways. Secondly, we demonstrate that active DNA demethylation of a heavily methylated GFP reporter plasmid by ectopically expressed DNMT3A or DNMT3B occurs in vivo in transfected human HEK 293 cells in culture. Furthermore, the extent of DNA demethylation by the DNMTs in this cell-based system is affected by Ca2+ homeostasis as well as by mutation of their putative active cysteines. These findings substantiate the roles of the vertebrate DNMTs as double-edged swords in DNA methylation-demethylation in vitro as well as in a cellular context.
Project description:The de novo DNA methyltransferase 3-like (Dnmt3L) is a catalytically inactive DNA methylase that has been previously shown to cooperate with Dnmt3a and Dnmt3b to methylate DNA. Dnmt3L is highly expressed in mouse embryonic stem cells (ESC) but its function in these cells is unknown. We here report that Dnmt3L is required for the differentiation of ESC into primordial germ cells (PGC) through activation of the homeotic gene Rhox5. By genome-wide analysis we found that Dnmt3L is a positive regulator of methylation at gene bodies of housekeeping genes and a negative regulator of methylation at promoters of bivalent genes. We demonstrate that Dnmt3L interacts with the Polycomb PRC2 complex in competition with the DNA methyl transferases Dnmt3a and Dnmt3b to maintain low the methylation level at H3H27me3 regions. Thus in ESC, Dnmt3L counteracts the activity of de novo DNA methylases to keep low the level of DNA methylation at developmental gene promoters. Examination of 5mC in shGFP and shDnmt3L ESC by MeDIP-Seq