Editing DNA methylation (section)

=== Repression of transposable elements ===

DNA methylation is a powerful transcriptional repressor, at least in CpG dense contexts. Transcriptional repression of protein-coding genes appears essentially limited to specific classes of genes that need to be silent permanently and in almost all tissues. While DNA methylation does not have the flexibility required for the fine-tuning of gene regulation, its stability is perfect to ensure the permanent silencing of [[transposable element]]s.<ref>{{cite journal | vauthors = Dahlet T, Argüeso Lleida A, Al Adhami H, Dumas M, Bender A, Ngondo RP, Tanguy M, Vallet J, Auclair G, Bardet AF, Weber M | display-authors = 6 | title = Genome-wide analysis in the mouse embryo reveals the importance of DNA methylation for transcription integrity | journal = Nature Communications | volume = 11 | issue = 1 | pages = 3153 | date = June 2020 | pmid = 32561758 | pmc = 7305168 | doi = 10.1038/s41467-020-16919-w | bibcode = 2020NatCo..11.3153D }}</ref> Transposon control is one of the most ancient functions of DNA methylation that is shared by animals, plants and multiple protists.<ref>{{cite journal | vauthors = Huff JT, Zilberman D | title = Dnmt1-independent CG methylation contributes to nucleosome positioning in diverse eukaryotes | journal = Cell | volume = 156 | issue = 6 | pages = 1286–1297 | date = March 2014 | pmid = 24630728 | pmc = 3969382 | doi = 10.1016/j.cell.2014.01.029 }}</ref> It is even suggested that DNA methylation evolved precisely for this purpose.<ref>{{cite journal | vauthors = Yoder JA, Walsh CP, Bestor TH | title = Cytosine methylation and the ecology of intragenomic parasites | journal = Trends in Genetics | volume = 13 | issue = 8 | pages = 335–340 | date = August 1997 | pmid = 9260521 | doi = 10.1016/s0168-9525(97)01181-5 | doi-access = free }}</ref>