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Topoisomerase VI participates to a chromatin barrier-like function that prevents heterochromatin spreading in euchromatic islands (HTS)

ABSTRACT: The plant Topoisomerase VI complex has been implicated in a wide array of biological processes but little is known about its precise molecular role. In this study, we provide evidence that Topo VI acts as a chromatin barrier between chromatin territories by interacting with methionine adenosyltransferases (MAT), which produce the universal donor of methyl groups S-adenosyl-methionine (SAM). We first show that pericentromeric transposable elements (TEs) are awakened whereas euchromatic island genes (EIGs) within heterochromatin are downregulated in mutants of the Topo VI complex. Consistent with this, the level of repressive H3K9me2 marks increases at EIGs loci while it decreases at TEs in a hypomorphic Topo VI mutant. We demonstrate that the Topo VI complex can interact with the SAM synthase MAT3 and drives it to TEs. A deficiency of Topo VI induces relocation of MAT3 from TEs to EIGs islands, leading to the levelling of the H3K9me2 mark and hence heterochromatin spreading.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE103924 | GEO | 2018/09/12

REPOSITORIES: GEO

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Topoisomerase VI participates to a chromatin barrier-like function that prevents heterochromatin spreading in euchromatic islands (mRNA microarray)

Project description:The plant Topoisomerase VI complex has been implicated in a wide array of biological processes but little is known about its precise molecular role. In this study, we provide evidence that Topo VI acts as a chromatin barrier between chromatin territories by interacting with methionine adenosyltransferases (MAT), which produce the universal donor of methyl groups S-adenosyl-methionine (SAM). We first show that pericentromeric transposable elements (TEs) are awakened whereas euchromatic island genes (EIGs) within heterochromatin are downregulated in mutants of the Topo VI complex. Consistent with this, the level of repressive H3K9me2 marks increases at EIGs loci while it decreases at TEs in a hypomorphic Topo VI mutant. We demonstrate that the Topo VI complex can interact with the SAM synthase MAT3 and drives it to TEs. A deficiency of Topo VI induces relocation of MAT3 from TEs to EIGs islands, leading to the levelling of the H3K9me2 mark and hence heterochromatin spreading.

2019-04-03 | GSE129248 | GEO

Transcriptome analysis upon Sin3A or Sam-S knockdown or both in Drosophila cultured S2 cells

Project description:The SIN3 histone modifying complex regulates the expression of multiple methionine catabolic genes including SAM synthetase (Sam-S) as well as the level of S-adenosyl-methionine (SAM). To further investigate the relationship between methionine catabolism and epigenetic regulation by SIN3, we identified genes controlled by SIN3 and SAM-S. As a global transcriptional regulator, SIN3 impacted a wide range of genes. Independently, SAM-S affected a narrow range of genes. Additional genes, however, were influenced in dual knockdown cells. At some genes, SIN3 and SAM-S act independently, for others, redundantly and for a third set, in opposition. Together, the results obtained in the study of SIN3, a cofactor associated with histone modification, and SAM-S, a metabolic enzyme, uncover a complex relationship on regulating transcription.

2019-11-26 | GSE129145 | GEO

Variation in DNA methylation patterns more common among maize inbreds than among tissues

Project description:Transposable elements (TEs) have the potential to act as controlling elements to influence the expression of genes and are often subject to heterochromatic silencing. The current paradigm suggests that heterochromatic silencing can spread beyond the borders of TEs and influence the chromatin state of neighboring low-copy sequences. This would allow TEs to condition obligatory or facilitated epialleles and act as controlling elements. The maize genome contains numerous families of class I TEs (retrotransposons) that are present in moderate to high copy numbers, and many are found in regions near genes, which provides an opportunity to test whether the spreading of heterochromatin from retrotransposons is prevalent. We have investigated the extent of heterochromatin spreading into DNA flanking each family of retrotransposons by profiling DNA methylation and di-methylation of lysine 9 of histone 3 (H3K9me2) in low-copy regions of the maize genome. RNA–seq was performed on three biological replicates of four tissues: 3rd leaf, immature ear (SRP013432), embryo and endosperm(SRP009313) for both B73 and Mo17.

2012-09-04 | E-MTAB-4318 | biostudies-arrayexpress

Set1/COMPASS repels heterochromatin invasion at euchromatic sites by disrupting Suv39/Clr4 activity and nucleosome stability

Project description:We report global occupancy of H3K9me2 and H3K4me3 in wild-type S. pombe and two mutant backgrounds - the deletion of heterochromatin antagonist epe1 and the double mutant absent epe1 and the H3K4 methyltransferase set1

2020-08-24 | GSE140067 | GEO

Enzymatic activation of the nitrogen atom in peptide bonds

Project description:Abstract The peptide bond is the defining feature of proteins, it co ntrols their structure by enforcing planarity and governs their chemistry by abolishing nucleophili city. This behaviour results from the delocalisation of the lone pair of electrons on the nitrogen atom into the adjacent carbonyl bond. Methylating an amide bond by conventional chemistry usually requires a metal to generate the amide anion. The OphA enzyme methyla tes amide bonds at pH 7 in water using S-adenosyl methionine (SAM) as co-factor. The st ructure of OphA reveals a complex catenane arrangement in which the substrate i s clamped adjacent to SAM. Site directed mutants have identified the key catalytic residue s. A mechanism in which conjugation of the peptide bond is disrupted by van der Waals in teractions between SAM and the amide nitrogen is proposed and tested. The methylation of amides is of particular interest as it greatly enhances the cell permeability of peptides.

2020-03-20 | PXD005934 | Pride

Proteome of rice shoot apical meristem

Project description:DNA methylation is an epigenetic modification that specifies the basic state of pluripotent stem cells and regulates the developmental transition from stem cells to various cell types. In flowering plants, the shoot apical meristem (SAM) contains a pluripotent stem cell population which generates the aerial part of plants including the germ cells. Under appropriate conditions, the SAM undergoes a developmental transition from a leaf-forming vegetative SAM to an inflorescence- and flower-forming reproductive SAM. While SAM characteristics are largely altered in this transition, the complete picture of DNA methylation remains elusive. Here, by analyzing whole-genome DNA methylation of isolated rice SAMs in the vegetative and reproductive stages, we found that methylation at CHH sites is kept high, particularly at transposable elements (TEs), in the vegetative SAM relative to the differentiated leaf, and increases in the reproductive SAM via the RNA-dependent DNA methylation pathway. We also found that half of the TEs that were highly methylated in gametes had already undergone CHH hypermethylation in the SAM. Our results indicate that changes in DNA methylation begin in the SAM long before germ cell differentiation to protect the genome from harmful TEs.

2020-08-14 | PXD020608 | Pride

Various modes of HP1a interactions with the euchromatic chromosome arms in Drosophila ovarian somatic cells

Project description:Heterochromatin protein 1a (HP1a) is a well-known component of pericentromeric and telomeric heterochromatin in Drosophila. However, its role and the mechanisms of its binding in the chromosome arms (ChAs) remain largely unclear. Here, we identified HP1a-interacting domains in the somatic cells of Drosophila ovaries using a DamIDseq approach and compared them with insertion sites of transposable elements (TEs) revealed by genome sequencing. Although HP1a domains cover only 13% of ChAs, they non-randomly associate with 42% of TE insertions. Furthermore, HP1a propagates from TE insertions at distances up to 10-kb. These data confirm the role of TEs in formation of HP1a islands in ChAs. However, only 18% of HP1a domains have adjacent TEs, indicating the existence of other mechanisms of HP1a domain formation besides spreading from TEs. In particular, many TE-independent HP1a domains correspond to the regions attached to the nuclear pore complexes (NPCs), or contain active gene promoters. Surprisingly, HP1a occupancy on the promoters of these genes does not lead to their repression. However, the steady-state transcript level of many genes located outside of HP1a domains was altered upon HP1a knockdown in the somatic cells of ovaries, thus pointing to the strong indirect effect of HP1a depletion. Collectively, our results support an existence of at least three different mechanisms of HP1a domain emergence in ChAs: spreading from TE insertions, interaction with the chromatin located near NPCs and targeting to the promoters of moderately expressed genes.

2020-05-26 | GSE132756 | GEO

Arabidopsis AGDP1 links H3K9me2 to DNA methylation in heterochromatin

Project description:Heterochromatin is a tightly packed form of DNA, which is associated with histone 3 lysine 9 methylation (H3K9me). Here, we identify an H3K9me2 binding protein, Agenet domain (AGD)-containing protein 1 (AGDP1), in Arabidopsis thaliana. Our biochemical studies revealed that the AGDP1 can specifically recognize the H3K9me2 marks by the three pairs of tandem-AGDs. We determined the crystal structure of the AGD12 of Raphanus sativus AGDP1 in complex with an H3K9me2 peptide. In the complex, the histone peptide adopts a unique helical conformation. AGD12 employs a newly defined interacting interface to specifically recognize the H3K4me0 and H3K9me2 marks. In addition, we found that AGDP1 is required for transcriptional gene silencing, non-CG DNA methylation, and H3K9 dimethylation. Our ChIP-seq data showed that AGDP1 is enriched in TE regions and associated with the heterochromatin marks. Our findings suggest that, as a heterochromatin binding protein, AGDP1 links H3K9me2 to DNA methylation in heterochromatin regions.

2018-10-23 | GSE111609 | GEO

Heterochromatin remodeling by CDK12 contributes to learning in Drosophila

Project description:We describe the epigenetic profiling of the H3K9me2 and HP1a in Drosophila third instar larvae before and after CDK12 depletion by RNA interference (RNAi). Here we show that CDK12 regulates heterochromatin dynamics in Drosophila chromosomes. Depletion of CDK12 induces the increased HP1a and H3K9me2 binding profile on the coding region of euchromatic genes, with the X chromosome being the most affected. These results are consistent with the polytene chromosome immunostaining pattern of HP1a and H3K9me2 after CDK12 knockdown in our initial cytological observations, which show that CDK12 depletion induce heterochromatin spreading on euchromatic arms, especially on the X chromosome. This study describes a novel role of the CDK12 complex in controlling the epigenetic transition between euchromatin and heterochromatin. Examination of the genome-wide H3K9me2 and HP1a binding profile in wildtype larvae (WT) and CDK12-depleted larvae (CDK12-KD). Examination of the genome-wide CDK12 binding profile in wildtype larvae (WT). Twelve independent immunoprecipitations were conducted for each antibody. Two biological replicates were performed.

2015-11-02 | E-GEOD-63011 | biostudies-arrayexpress

Heterochromatin remodeling by CDK12 contributes to learning in Drosophila

2015-11-02 | GSE63011 | GEO

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