Editing Methylation (section)

====Protein methylation====
[[Protein methylation]] typically takes place on [[arginine]] or [[lysine]] [[amino acid]] residues in the protein sequence.<ref>{{cite book |last1=Walsh |first1=Christopher |chapter=Protein Methylation |pages=121–149 |chapter-url={{GBurl|JGBfQXIzdwgC|p=121}} |title=Posttranslational Modification of Proteins: Expanding Nature's Inventory |date=2006 |publisher=Roberts and Company Publishers |isbn=978-0-9747077-3-0 }}</ref> {{anchor|Arginine methylation}}Arginine can be methylated once (monomethylated arginine) or twice, with either both methyl groups on one terminal nitrogen ([[asymmetric dimethylarginine]]) or one on both nitrogens (symmetric dimethylarginine), by [[protein arginine methyltransferases]] (PRMTs). Lysine can be methylated once, twice, or three times by [[lysine methyltransferases]]. Protein methylation has been most studied in the [[histone]]s. The transfer of [[methyl]] groups from [[S-adenosyl methionine]] to histones is catalyzed by enzymes known as [[histone methyltransferase]]s. Histones that are methylated on certain residues can act [[Epigenetics|epigenetically]] to repress or activate gene expression.<ref name="Grewal2004">{{cite journal |last1=Grewal |first1=Shiv IS |last2=Rice |first2=Judd C |title=Regulation of heterochromatin by histone methylation and small RNAs |journal=Current Opinion in Cell Biology |date=June 2004 |volume=16 |issue=3 |pages=230–238 |doi=10.1016/j.ceb.2004.04.002 |pmid=15145346 |url=https://zenodo.org/record/1258832 }}</ref><ref name="Nakayama2001">{{cite journal |last1=Nakayama |first1=Jun-ichi |last2=Rice |first2=Judd C. |last3=Strahl |first3=Brian D. |last4=Allis |first4=C. David |last5=Grewal |first5=Shiv I. S. |title=Role of Histone H3 Lysine 9 Methylation in Epigenetic Control of Heterochromatin Assembly |journal=Science |date=6 April 2001 |volume=292 |issue=5514 |pages=110–113 |doi=10.1126/science.1060118 |pmid=11283354 |bibcode=2001Sci...292..110N }}</ref> Protein methylation is one type of [[post-translational modification]].