NCIt definition : A change in the amino acid residue at position 27 in histone H3 where lysine has been
replaced by another amino acid.;
NCIt note : Even though the literature refers to lysine 27 methylation or amino acid variation/mutation,
RefSeq indicates that the lysine is located at amino acid position 28 in histone H3.
(see https://link.springer.com/article/10.1007/s00401-018-1867-2);