CG Methylation

Abstract

A striking feature of mammalian genomes is the paucity of the CG dinucleotide. There are approximately 20,000 regions termed CpG islands where CGs cluster. This represents 5% of all CGs and 1% of the genome. CpG islands are typically unmethylated and are often promoters for housekeeping genes. The remaining 95% of CG dinucleotides are disposed throughout 99% of the genome and are typically methylated and found in half of all promoters. CG methylation facilitates binding of the C/EBP family of transcription factors, proteins critical for differentiation of many tissues. This allows these proteins to localize in the methylated CG poor regions of the genome where they may produce advantageous changes in gene expression at nearby or more distant regions of the genome. In this review, our growing understanding of the consequences of CG methylation will be surveyed.

Epigenetic Regulation of KLHL34 Predictive of Pathologic Response to Preoperative Chemoradiation Therapy in Rectal Cancer Patients

“…DNA methylation at CpG island promoter regions regulates gene expression (15,16). Based on these studies, we focused on the analysis of CpG island promoter regions to identify differentially methylated regions in radiation responsive and nonresponsive tissues.…”

Epigenetic regulation by DNA methylation and miRNA molecules in cancer

“…CpGs outside of transcription start sites are also sites of transcriptional initiation during development and become methylated hence lose these properties. Silencing of CGI promoters by methylation and demethylation reactions is differentially sensitive to the distance between interacting CpGs (CpG clustering) [3], and accomplished through dense CpG methylation or polycomb recruitment. CGIs are therefore equipped to influence local chromatin structure and simplify regulation of gene activity.…”

CG methylated microarrays identify a novel methylated sequence bound by the CEBPB|ATF4 heterodimer that is active in vivo

“…When compared between different cells, they have active unmethylated promoters in common, but the active methylated promoters are different, suggesting that many methylated promoters can be active depending on cell type. In contrast to CGI where methylation suppresses gene expression, the effect of methylation on gene expression in active CG-poor tissue-specific promoters is less clear (Bird 1986;Vinson and Chatterjee 2012). Tissue-specific promoter demethylation sometimes accompanies gene expression but typically occurs after the methylated promoter becomes active (Grainger et al 1983).…”