Gene Silencing Triggers Polycomb Repressive Complex 2 Recruitment to CpG Islands Genome Wide

The strict suppression and reprogramming of gene expression are necessary at different development stages and/or in response to environment stimuli in eukaryotes. In Rice Magnaporthe oryzae pathosystem, effectors from pathogen are kept transcriptionally silenced in the vegetative growth stage and are highly expressed during invasive growth stage to adapt to the host environment. However, the mechanism of how such effectors are stably repressed in the vegetative stage and its roles during rice blast infection remain unclear so far. Here, we showed that all subunits of Polycomb Repressive Complex 2 are required for such repression by direct H3K27me3 occupancy and pathogenic process in M. oryzae. Suppression of polycomb-mediated H3K27me3 causes an improper induction of effectors during vegetative growth thus simulating a host environment. Notably, the addition subunit P55 not only acts as the bridge to connect with core subunits to form a complex in M. oryzae, but also recruits Sin3 histone deacetylase complex to prompt H3K27me3 occupancy for stable maintenance of transcriptional silencing of the target genes in the absence of PRC1. In contrast, during invasive growth stage, the repressed state of effectors chromatin can be partially erased during pathogenic development resulting in transcriptional activation of effectors therein. Overall, Polycomb repressive complex 2 coordinates with Sin3 histone deacetylase complex to epigenetically reprogram genome-wide expression of effectors, which act as molecular switch to memorize the host environment from vegetative to invasive growth, thus contributing to the infection of rice blast.

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Bending and looping of long DNA by Polycomb repressive complex 2 revealed by AFM imaging in liquid

Nucleic Acids Research ◽

10.1093/nar/gkaa073 ◽

2020 ◽

Vol 48 (6) ◽

pp. 2969-2981 ◽

Cited By ~ 2

Author(s):

Patrick R Heenan ◽

Xueyin Wang ◽

Anne R Gooding ◽

Thomas R Cech ◽

Thomas T Perkins

Keyword(s):

Gene Silencing ◽

Single Molecule ◽

Molecular Mechanisms ◽

Cpg Island ◽

Specific Binding ◽

Gc Content ◽

Polycomb Repressive Complex ◽

Apparent Dissociation Constant ◽

Polycomb Repressive Complex 2 ◽

Epigenetic Gene Silencing

Abstract Polycomb repressive complex 2 (PRC2) is a histone methyltransferase that methylates histone H3 at Lysine 27. PRC2 is critical for epigenetic gene silencing, cellular differentiation and the formation of facultative heterochromatin. It can also promote or inhibit oncogenesis. Despite this importance, the molecular mechanisms by which PRC2 compacts chromatin are relatively understudied. Here, we visualized the binding of PRC2 to naked DNA in liquid at the single-molecule level using atomic force microscopy. Analysis of the resulting images showed PRC2, consisting of five subunits (EZH2, EED, SUZ12, AEBP2 and RBBP4), bound to a 2.5-kb DNA with an apparent dissociation constant ($K_{\rm{D}}^{{\rm{app}}}$) of 150 ± 12 nM. PRC2 did not show sequence-specific binding to a region of high GC content (76%) derived from a CpG island embedded in such a long DNA substrate. At higher concentrations, PRC2 compacted DNA by forming DNA loops typically anchored by two or more PRC2 molecules. Additionally, PRC2 binding led to a 3-fold increase in the local bending of DNA’s helical backbone without evidence of DNA wrapping around the protein. We suggest that the bending and looping of DNA by PRC2, independent of PRC2’s methylation activity, may contribute to heterochromatin formation and therefore epigenetic gene silencing.

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Genome-wide analysis identifies a functional association of Tet1 and Polycomb repressive complex 2 in mouse embryonic stem cells

Genome Biology ◽

10.1186/gb-2013-14-8-r91 ◽

2013 ◽

Vol 14 (8) ◽

pp. R91 ◽

Cited By ~ 100

Author(s):

Francesco Neri ◽

Danny Incarnato ◽

Anna Krepelova ◽

Stefania Rapelli ◽

Andrea Pagnani ◽

...

Keyword(s):

Stem Cells ◽

Embryonic Stem Cells ◽

Embryonic Stem ◽

Mouse Embryonic Stem Cells ◽

Polycomb Repressive Complex ◽

Functional Association ◽

Polycomb Repressive Complex 2 ◽

Genome Wide Analysis ◽

Genome Wide

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Genome-Wide De Novo Methylation in Epithelial Ovarian Cancer

International Journal of Gynecological Cancer ◽

10.1097/igc.0b013e31820e5cda ◽

2011 ◽

Vol 21 (2) ◽

pp. 269-279 ◽

Cited By ~ 13

Author(s):

Rachel Michaelson-Cohen ◽

Ilana Keshet ◽

Ravid Straussman ◽

Merav Hecht ◽

Howard Cedar ◽

...

Keyword(s):

Ovarian Cancer ◽

Cell Differentiation ◽

Gene Silencing ◽

De Novo ◽

Cpg Islands ◽

Aberrant Methylation ◽

Genome Wide ◽

A Genome ◽

Treatment Responsiveness ◽

De Novo Methylation

Background:DNA methylation regulates gene expression during development. The methylation pattern is established at the time of implantation. CpG islands are genome regions usually protected from methylation; however, selected islands are methylated later. Many undergo methylation in cancer, causing epigenetic gene silencing. Aberrant methylation occurs early in tumorigenesis, in a specific pattern, inhibiting differentiation.Although methylation of specific genes in ovarian tumors has been demonstrated in numerous studies, they represent only a fraction of all methylated genes in tumorigenesis.Objectives:To explore the hypermethylation design in ovarian cancer compared with the methylation profile of normal ovaries, on a genome-wide scale, thus shedding light on the role of gene silencing in ovarian carcinogenesis.Identifying genes that undergo de novo methylation in ovarian cancer may assist in creating biomarkers for disease diagnosis, prognosis, and treatment responsiveness.Methods:DNA was collected from human epithelial ovarian cancers and normal ovaries. Methylation was detected by immunoprecipitation using 5-methyl-cytosine-antibodies. DNA was hybridized to a CpG island microarray containing 237,220 gene promoter probes. Results were analyzed by hybridization intensity, validated by bisulfite analysis.Results:A total of 367 CpG islands were specifically methylated in cancer cells. There was enrichment of methylated genes in functional categories related to cell differentiation and proliferation inhibition. It seems that their silencing enables tumor proliferation.Conclusions:This study provides new perspectives on methylation in ovarian carcinoma, genome-wide. It illustrates how methylation of CpG islands causes silencing of genes that have a role in cell differentiation and functioning. It creates potential biomarkers for diagnosis, prognosis, and treatment responsiveness.

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