Editing CpG site (section)

=== CpG islands in promoters ===

In humans, about 70% of [[Promoter (genetics)|promoters]] located near the [[transcription start site]] of a gene (proximal promoters) contain a [[#CpG islands|CpG island]].<ref name="pmid16432200"/><ref name="pmid21576262"/>

[[Distal promoter]] elements also frequently contain CpG islands. An example is the DNA repair gene ''[[ERCC1]]'', where the CpG island-containing element is located about 5,400 nucleotides upstream of the [[Transcription (biology)|transcription start site]] of the ''ERCC1'' gene.<ref name="pmid19626585">{{cite journal |vauthors=Chen HY, Shao CJ, Chen FR, Kwan AL, Chen ZP |title=Role of ERCC1 promoter hypermethylation in drug resistance to cisplatin in human gliomas |journal=Int. J. Cancer |volume=126 |issue=8 |pages=1944–54 |year=2010 |pmid=19626585 |doi=10.1002/ijc.24772 |doi-access=free }}</ref> CpG islands also occur frequently in promoters for [[Noncoding DNA#Noncoding functional RNA|functional noncoding RNAs]] such as [[microRNA]]s.<ref name="pmid27573897">{{cite book |vauthors=Kaur S, Lotsari-Salomaa JE, Seppänen-Kaijansinkko R, Peltomäki P |title=Non-coding RNAs in Colorectal Cancer |chapter=MicroRNA Methylation in Colorectal Cancer |volume=937 |pages=109–22 |year=2016 |pmid=27573897 |doi=10.1007/978-3-319-42059-2_6 |series=Advances in Experimental Medicine and Biology |isbn=978-3-319-42057-8 }}</ref>