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Arabidopsis MORC proteins function in the efficient establishment of RNA directed DNA methylation

ABSTRACT: The Microrchidia (MORC) family of ATPases are required for transposable element (TE) silencing and heterochromatin condensation in plants and animals, and C. elegans MORC-1 has been shown to topologically entrap and condense DNA. In Arabidopsis thaliana, mutation of MORCs has been shown to reactivate silent methylated genes and transposons and to decondense heterochromatic chromocenters, despite only minor changes in the maintenance of DNA methylation. Here we provide the first evidence localizing Arabidopsis MORC proteins to specific regions of chromatin and find that MORC4 and MORC7 are closely co-localized with sites of RNA directed DNA methylation (RdDM). We further show that MORC7, when tethered to DNA by an artificial zinc finger, can facilitate the establishment of RdDM. Finally, we show that MORCs are required for the efficient RdDM mediated establishment of DNA methylation and silencing of a newly integrated FWA transgene, even though morc mutations have no effect on the maintenance of preexisting methylation at the endogenous FWA gene. We propose that MORCs function as a molecular tether in RdDM complexes to reinforce RdDM activity for methylation establishment. These findings have implications for MORC protein function in a variety of other eukaryotic organisms.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE160285 | GEO | 2021/07/02

REPOSITORIES: GEO

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Arabidopsis MORC proteins function in the efficient establishment of RNA directed DNA methylation

Project description:The Microrchidia (MORC) family of ATPases are required for transposable element (TE) silencing and heterochromatin condensation in plants and animals, and C. elegans MORC-1 has been shown to topologically entrap and condense DNA. In Arabidopsis thaliana, mutation of MORCs has been shown to reactivate silent methylated genes and transposons and to decondense heterochromatic chromocenters, despite only minor changes in the maintenance of DNA methylation. Here we provide the first evidence localizing Arabidopsis MORC proteins to specific regions of chromatin and find that MORC4 and MORC7 are closely co-localized with sites of RNA directed DNA methylation (RdDM). We further show that MORC7, when tethered to DNA by an artificial zinc finger, can facilitate the establishment of RdDM. Finally, we show that MORCs are required for the efficient RdDM mediated establishment of DNA methylation and silencing of a newly integrated FWA transgene, even though morc mutations have no effect on the maintenance of preexisting methylation at the endogenous FWA gene. We propose that MORCs function as a molecular tether in RdDM complexes to reinforce RdDM activity for methylation establishment. These findings have implications for MORC protein function in a variety of other eukaryotic organisms.

2021-07-02 | PXD026674 | Pride

MORC proteins regulate transcription factor binding through mediating chromatin compaction at active chromatin regions

Project description:The Microrchidia (MORC) family proteins are evolutionarily conserved GHKL type ATPases involved in chromatin compaction and gene silencing. Arabidopsis MORC proteins act in the RNA-directed DNA methylation (RdDM) pathway where they act as molecular tethers to ensure the efficient establishment of RdDM and de novo gene silencing. However, they also have RdDM independent functions in which the underlying mechanism is unknown. In this study, we examined MORC binding regions that are devoid of RdDM to shed light on MORCs RdDM independent functions. We found that MORC proteins can compact chromatin, exclude the accessibility of DNA to transcription factors (TFs) and thereby repress gene expression. We also found that MORC-mediated repression is particularly important under stress conditions. In addition, we showed that MORC proteins may regulate TFs through direct or indirect interactions. These TFs in turn regulate their own transcription, indicating a feedforward loop. Our findings provide insights into the molecular mechanisms of MORC-mediated chromatin compaction and transcription regulation.

2023-03-27 | GSE212801 | GEO

The MOM1 complex recruits the RdDM machinery via MORC6 to establish de novo DNA methylation.

Project description:MOM1 is an Arabidopsis factor previously shown to mediate transcriptional silencing independent of major DNA methylation changes. Here we found that MOM1 localizes with sites of RNA-directed DNA methylation (RdDM). Tethering MOM1 with artificial zinc finger to unmethylated FWA promoter led to establishment of DNA methylation and FWA silencing. This process was blocked by mutations in components of the Pol V arm of the RdDM machinery, as well as by mutation of MORC6. We found that at some endogenous RdDM sites, MOM1 is required to maintain DNA methylation and a closed chromatin state. In addition, efficient silencing of newly introduced FWA transgenes was impaired by mutation of MOM1 or mutation of genes encoding the MOM1 interacting PIAL1/2 proteins. In addition to RdDM sites, we identified a group of MOM1 peaks at active chromatin near genes that colocalized with MORC6. These findings demonstrate a multifaceted role of MOM1 in genome regulation.

2023-06-10 | PXD039991 | Pride

The MOM1 complex recruits the RdDM machinery via MORC6 to establish de novo DNA methylation.

Project description:MOM1 is an Arabidopsis factor previously shown to mediate transcriptional silencing independent of major DNA methylation changes. Here we found that MOM1 localizes with sites of RNA-directed DNA methylation (RdDM). Tethering MOM1 with artificial zinc finger to unmethylated FWA promoter led to establishment of DNA methylation and FWA silencing. This process was blocked by mutations in components of the Pol V arm of the RdDM machinery, as well as by mutation of MORC6. We found that at some endogenous RdDM sites, MOM1 is required to maintain DNA methylation and a closed chromatin state. In addition, efficient silencing of newly introduced FWA transgenes was impaired by mutation of MOM1 or mutation of genes encoding the MOM1 interacting PIAL1/2 proteins. In addition to RdDM sites, we identified a group of MOM1 peaks at active chromatin near genes, again colocalized with MORC6. These findings demonstrate a multifaceted role of MOM1 in genome regulation.

2023-06-09 | GSE221679 | GEO

MORC family ATPases required for heterochromatin condensation and gene silencing

Project description:Transposable elements (TEs) and DNA repeats are commonly targeted by DNA and histone methylation to achieve epigenetic gene silencing. We isolated mutations in two Arabidopsis genes, CRT1 and CRH6, which cause de-repression of DNA-methylated genes and TEs, but no losses of DNA or histone methylation. CRT1 and CRH6 are members of the conserved Microrchidia (MORC) ATPase family, predicted to catalyze alterations in chromosome superstructure. The crt1 and crh6 mutants show decondensation of pericentromeric heterochromatin, increased interaction of pericentromeric regions with the rest of the genome, and transcriptional defects that are largely restricted to loci residing in pericentromeric regions. Knockdown of the single MORC homolog in Caenorhabditis elegans also impairs transgene silencing. We propose that the MORC ATPases are conserved regulators of gene silencing in eukaryotes. For Col wild type control and each of two T-DNA mutants, a single sample each of small RNA (sRNA), mRNA-Seq, 5'-methylcytosine DNA methylation (BS-Seq), ChIP H3K9me2 histone methylation, and ChIP H3 histone control. For each of two EMS mutants, and as controls, their respective backgrounds, two batches of single mRNA samples, with the first batch also having a single mRNA sample for a double EMS mutant.

2012-05-02 | E-GEOD-37644 | biostudies-arrayexpress

MORC family ATPases required for heterochromatin condensation and gene silencing

2012-05-03 | GSE37644 | GEO

Arabidopsis MORC proteins function in the efficient establishment of RNA directed DNA methylation

Project description:Arabidopsis MORC proteins function in the efficient establishment of RNA directed DNA methylation

| PRJNA672885 | ENA

Arabidopsis AtMORC4 and AtMORC7 form Nuclear Bodies and Repress a Large Number of Protein-Coding Genes

Project description:The MORC family of GHKL ATPases are an enigmatic class of proteins with diverse chromatin related functions. In Arabidopsis, AtMORC1, AtMORC2, and AtMORC6 act together in heterodimeric complexes to mediate transcriptional silencing of methylated DNA elements. Here, we studied Arabidopsis AtMORC4 and AtMORC7. We found that, in contrast to AtMORC1,2,6, they act to suppress a wide set of non-methylated protein-coding genes that are enriched for those involved in pathogen response. Furthermore, atmorc4 atmorc7 double mutants show a pathogen response phenotype. We found that AtMORC4 and AtMORC7 form homomeric complexes in vivo and are concentrated in discrete nuclear bodies adjacent to chromocenters. Analysis of an atmorc1,2,4,5,6,7 hextuple mutant demonstrates that transcriptional de-repression is largely uncoupled from changes in DNA methylation in plants devoid of MORC function. However, we also uncover a requirement for MORC in both DNA methylation and silencing at a small but distinct subset of RNA-directed DNA methylation target loci. These regions are characterized by poised transcriptional potential and a low density of sites for symmetric cytosine methylation. These results provide insights into the biological function of MORC proteins in higher eukaryotes.

2016-05-11 | GSE78836 | GEO

morc-1 regulates transgenerational heterochromatin maintenance at nuclear RNAi targets

Project description:The germline is an immortal cell lineage and therefore must accurately transmit genetic and epigenetic information over infinite cell divisions to ensure fertility and species survival. Endogenous siRNAs (endo-siRNAs), which are highly expressed in the parental germline and inherited in their progeny, represent one mechanism by which epigenetic information can be transmitted from one generation to the next. In C. elegans, this is accomplished by the nuclear RNAi pathway, which ensures robust inheritance of endo-siRNAs and of target gene silencing through deposition of H3K9me3 marks at target loci. How these marks are maintained in subsequent generations is unknown. Here, we show that the C. elegans micro-orchidia homolog, MORC-1, functions downstream of endo-siRNAs to mediate target silencing and maintenance of siRNA-dependent H3K9me3 marks. Like the established members of the nuclear RNAi pathway, morc-1 is essential for germline maintenance and thus morc-1(-) mutants exhibit a mortal germline phenotype. Furthermore, morc-1(-) mutants exhibit severe decondensation of germline chromatin. Through a forward genetic screen, we have identified mutations in the gene encoding MET-1, a H3K36 histone methyltransferase, that potently suppress morc-1(-) germline mortality. We show that morc-1(-) mutants exhibit progressive, met-1-dependent enrichment of H3K36me3 and that mutation of met-1 can restore germline chromatin organization in late generation morc-1(-) mutants. Our data suggest that MORC-1 is required to repress MET-1 activity at nuclear RNAi target genes and that in the absence of this repression, MET-1-mediated encroachment of euchromatin leads to detrimental decondensation of germline chromatin and germline mortality.

2017-05-22 | GSE89887 | GEO

MORC1 represses transposable elements in the mouse male germ line

Project description:The Microrchidia (Morc) family of GHKL ATPases are present in a wide variety of prokaryotic and eukaryotic organisms but are of largely unknown function. Genetic screens in Arabidopsis thaliana have identified Morc genes as important repressors of transposons and other DNA methylated and silent genes. MORC1 deficient mice were previously found to display male-specific germ cell loss and infertility. Here we show that MORC1 is responsible for transposon repression in the male germline in a pattern that is similar to that observed for germ cells deficient for the DNA methyltransferase homolog DNMT3L. Morc1 mutants show highly localized defects in the establishment of DNA methylation at specific classes of transposons, and this is associated with failed transposon silencing at these sites. Our results identify MORC1 as an important new regulator of the epigenetic landscape of male germ cells during the period of global de novo methylation. This data includes: 47 RNA-seq, 4 smRNA-seq, 6 BS-seq, and 2 ChIP-seq datasets

2014-12-12 | E-GEOD-63048 | biostudies-arrayexpress

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