CpG islands – ‘A rough guide’

Abstract 

Mammalian genomes are punctuated by DNA sequences containing an atypically high frequency of CpG sites termed CpG islands (CGIs). CGIs generally lack DNA methylation and associate with the majority of annotated gene promoters. Many studies, however, have identified examples of CGI methylation in malignant cells, leading to improper gene silencing. CGI methylation also occurs in normal tissues and is known to function in X-inactivation and genomic imprinting. More recently, differential methylation has been shown between tissues, suggesting a potential role in transcriptional regulation during cell specification. Many of these tissue-specific methylated CGIs localise to regions distal to promoters, the regulatory function of which remains to be determined.

Abbreviations: CGIs, CpG islands, TSS, transcription start site, ES cells, embryonic stem cells, CGBP, CpG-binding protein, MAGE, melanoma antigen encoding genes, RLGS, restriction landmark genome scanning, HOX, Homeobox, ncRNA, non-coding RNA, RACE, rapid amplification of cDNA ends

Keywords: CpG Island, Computational prediction, DNA methylation, Transcriptional regulation