CG suppression

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Methylation and deamination of cytosine to thymine

The CG-suppression (or CpG suppression) refers to a lower frequency of CpG dinucleotides , particularly in the genomes of vertebrates .

properties

In somatic cells , cytosines are predominantly methylated in the DNA , and in CpG dinucleotides mostly on both DNA strands. Methylated cytosines tend to deaminate spontaneously . The deamination to thymine following methylation reduces the frequency of CpG dinucleotides in methylated DNA. This creates a TpG from the CpG. This creates an accumulation of TpG in the genome and, on the complementary second DNA strand, its complementary counterpart CpA.

Deamination of unmethylated cytosine, on the other hand , produces uracil , which is corrected again in the course of DNA repair . Unmethylated CpG dinucleotides occur predominantly in CpG islands , methylated CpG dinucleotides there only rarely.

Since the GC proportion of human DNA is around 42%, a frequency of 0.21², corresponding to 4.41%, would be expected if the distribution was uniform. Due to CG suppression, CpG dinucleotides are less than 1% in the genome.

literature

  • Y. Iwasaki, T. Abe, N. Okada, K. Wada, Y. Wada, T. Ikemura: Evolutionary changes in vertebrate genome signatures with special focus on coelacanth. In: DNA research: an international journal for rapid publication of reports on genes and genomes. Volume 21, number 5, October 2014, pp. 459-467, doi : 10.1093 / dnares / dsu012 , PMID 24800745 , PMC 4195492 (free full text).

Individual evidence

  1. ↑ Guenter Kahl: The Dictionary of Genomics, Transcriptomics and Proteomics. John Wiley & Sons, 2015, ISBN 978-3-527-67866-2 , p. 272.
  2. ↑ Law J, Jacobsen SE: Establishing, maintaining and modifying DNA methylation patterns in plants and animals . In: Nat. Rev. Genet. . 11, No. 3, 2010, pp. 204-220. doi : 10.1038 / nrg2719 . PMID 20142834 . PMC 3034103 (free full text).
  3. ↑ International Human Genome Sequencing Consortium: Initial sequencing and analysis of the human genome . In: Nature . 409, No. 6822, February 2001, pp. 860-921. doi : 10.1038 / 35057062 . PMID 11237011 .
  4. ↑ Donald R. Forsdyke: Evolutionary Bioinformatics. Springer, 2016, ISBN 978-3-319-28755-3 , p. 356.