TRANSCRIPTIONAL REGULATION OF HYAL-2 HYALURONIDASE BY DE NOVO METHYLATION OF CpG ISLANDS IN BRAIN

Recent studies showing a correlation between the levels of DNA (cytosine-5-)-methyltransferase (DNA MTase) enzyme activity and tumorigenicity have implicated this enzyme in the carcinogenic process. Moreover, hypermethylation of CpG island-containing promoters is associated with the inactivation of genes important to tumor initiation and progression. One proposed role for DNA MTase in tumorigenesis is therefore a direct role in the de novo methylation of these otherwise unmethylated CpG islands. In this study, we sought to determine whether increased levels of DNA MTase could directly affect CpG island methylation. A full-length cDNA for human DNA MTase driven by the cytomegalovirus promoter was constitutively expressed in human fibroblasts. Individual clones derived from cells transfected with DNA MTase (HMT) expressed 1- to 50-fold the level of DNA MTase protein and enzyme activity of the parental cell line or clones transfected with the control vector alone (Neo). To determine the effects of DNA MTase overexpression on CpG island methylation, we examined 12 endogenous CpG island loci in the HMT clones. HMT clones expressing > or = 9-fold the parental levels of DNA MTase activity were significantly hypermethylated relative to at least 11 Neo clones at five CpG island loci. In the HMT clones, methylation reached nearly 100% at susceptible CpG island loci with time in culture. In contrast, there was little change in the methylation status in the Neo clones over the same time frame. Taken together, the data indicate that overexpression of DNA MTase can drive the de novo methylation of susceptible CpG island loci, thus providing support for the idea that DNA MTase can contribute to tumor progression through CpG island methylation-mediated gene inactivation.

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Role of transcription complexes in the formation of the basal methylation pattern in early development

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1804755115 ◽

2018 ◽

Vol 115 (41) ◽

pp. 10387-10391 ◽

Cited By ~ 4

Author(s):

Razi Greenfield ◽

Amalia Tabib ◽

Ilana Keshet ◽

Joshua Moss ◽

Ofra Sabag ◽

...

Keyword(s):

De Novo ◽

Cpg Islands ◽

Embryonic Stem ◽

Methylation Pattern ◽

Entire Genome ◽

Genome Wide ◽

Topological Pattern ◽

Histone H3k4 ◽

Transcription Complexes ◽

De Novo Methylation

Following erasure in the blastocyst, the entire genome undergoes de novo methylation at the time of implantation, with CpG islands being protected from this process. This bimodal pattern is then preserved throughout development and the lifetime of the organism. Using mouse embryonic stem cells as a model system, we demonstrate that the binding of an RNA polymerase complex on DNA before de novo methylation is predictive of it being protected from this modification, and tethering experiments demonstrate that the presence of this complex is, in fact, sufficient to prevent methylation at these sites. This protection is most likely mediated by the recruitment of enzyme complexes that methylate histone H3K4 over a local region and, in this way, prevent access to the de novo methylation complex. The topological pattern of H3K4me3 that is formed while the DNA is as yet unmethylated provides a strikingly accurate template for modeling the genome-wide basal methylation pattern of the organism. These results have far-reaching consequences for understanding the relationship between RNA transcription and DNA methylation.

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Correction: Nucleosomes Correlate with In Vivo Progression Pattern of De Novo Methylation of p16 CpG Islands in Human Gastric Carcinogenesis

PLoS ONE ◽

10.1371/annotation/eb15769c-aa54-4963-8a13-1dd7e8242319 ◽

2012 ◽

Vol 7 (8) ◽

Cited By ~ 5

Author(s):

Zhe-Ming Lu ◽

Jing Zhou ◽

Xiuhong Wang ◽

Zhenpo Guan ◽

Hua Bai ◽

...

Keyword(s):

De Novo ◽

Cpg Islands ◽

Gastric Carcinogenesis ◽

De Novo Methylation

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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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Roles of Cell Division and Gene Transcription in the Methylation of CpG Islands

Molecular and Cellular Biology ◽

10.1128/mcb.19.10.6690 ◽

1999 ◽

Vol 19 (10) ◽

pp. 6690-6698 ◽

Cited By ~ 84

Author(s):

Christina M. Bender ◽

Mark L. Gonzalgo ◽

Felicidad A. Gonzales ◽

Carvell T. Nguyen ◽

Keith D. Robertson ◽

...

Keyword(s):

Cell Division ◽

Gene Transcription ◽

De Novo ◽

Cpg Island ◽

Cpg Islands ◽

Exon 2 ◽

T24 Cells ◽

The Relationship ◽

Kinetics Of ◽

De Novo Methylation

ABSTRACT De novo methylation of CpG islands within the promoters of eukaryotic genes is often associated with their transcriptional repression, yet the methylation of CpG islands located downstream of promoters does not block transcription. We investigated the kinetics of mRNA induction, demethylation, and remethylation of the p16promoter and second-exon CpG islands in T24 cells after 5-aza-2′-deoxycytidine (5-Aza-CdR) treatment to explore the relationship between CpG island methylation and gene transcription. The rates of remethylation of both CpG islands were associated with time but not with the rate of cell division, and remethylation of thep16 exon 2 CpG island occurred at a higher rate than that of the p16 promoter. We also examined the relationship between the remethylation of coding sequence CpG islands and gene transcription. The kinetics of remethylation of the p16exon 2, PAX-6 exon 5, c-ABL exon 11, andMYF-3 exon 3 loci were examined following 5-Aza-CdR treatment because these genes contain exonic CpG islands which are hypermethylated in T24 cells. Remethylation occurred most rapidly in the p16, PAX-6, and c-ABL genes, shown to be transcribed prior to drug treatment. These regions also exhibited higher levels of remethylation in single-cell clones and subclones derived from 5-Aza-CdR-treated T24 cells. Our data suggest that de novo methylation is not restricted to the S phase of the cell cycle and that transcription through CpG islands does not inhibit their remethylation.

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