CpG Islands

From The School of Biomedical Sciences Wiki
Jump to: navigation, search

CpG Islands are short sequences, rich in cytosine and guanine bases (C and G), spread across DNA[1]. These sequences are around 100-1000 bp with a higher than usual CG sequence content, mostly found in promoter regions[2]. In mammals, most cytosine residues followed by a guanine residue are methylated, however, most 'C's in CpG Islands escape methylation, we call this hypomethylation. The methylation of CpG islands results in the switching off of transcription. Therefore, CpG islands enhance transcription. This is important in mammals as 60%-70% of protein-coding genes lack TATA and initiators causing transcription to occur at a lower rate.

In mammals, most C residues followed by a G are methylated to 5-methyl C. However, generally, C residues in CpG islands escape methylation (they are hypomethylated), this is important for protein function. Methylation of CpG islands is associated with silencing[3].

CpG islands in the mammalian genome, are associated with the start of the genome (the promotor region)[4]. CpG islands have been found in 40% of promoters in mammalian genes[5]. CpG islands often are the promoters of so-called housekeeping genes, genes that are almost constantly required but at a lower level than would be produced by a gene with a TATA box promoter[6].

References

  1. DEATON AM, BIRD A, CpG islands and the regulation of transcription, 2011,25(10),1010-1022
  2. Harvey Lodish, et al. Molecular Cell Biology. 8th ed. 2016. New York: W.H.Freeman Macmillan Learning. p.372.
  3. Zachariah RM, Rastegar M (2012) Linking epigenetics to human disease and Rett syndrome: the emerging novel and challenging concepts in MeCP2 research. Neural Plast 2012: 415825
  4. https://en.wikipedia.org/wiki/CpG_site#CpG_islands
  5. https://en.wikipedia.org/wiki/CpG_site#CpG_islands
  6. Harvey Lodish, et al. Molecular Cell Biology. 8th ed. 2016. New York: W.H.Freeman Macmillan Learning. p.372.
Personal tools
Namespaces
Variants
Actions
Navigation
Toolbox