BackgroundInformation | HistonesarenuclearproteinsthatformoctamericstructureswhichbindDNAtoformunitsofchromatincallednucleosomes.Thefamilyofhistones—H2A,H2B,H3,andH4—arekeyplayersingeneregulation.Theyundergoanumberofpost-translationalmodifications(PTM)inresponsetovariousstimuli,includingphosphorylationonserineandthreonineresiduesandmethylationonlysineresidues.PTMsproduceconfiguralchangesinhistoneproteinsthatmayinducenucleosomeremodelingandexposeorhideDNAsequencesfromtranscriptionalcomplexes.HistoneH4lysine20(H4K20)mayundergomono-,di-,ortrimethylation,whichiscatalyzedbythemethyltransferasePR-Set7(Set8orKMT5a).MethylatedH4K20playsaroleinregulatingDNAdamageresponses,mitosis,DNAreplication,andgeneexpression.TrimethylationofH4K20contributestogenesilencing,andisamarkoftherepressiveheterochromatinstate. |