Editing Histone (section)

=== Metazoan ===
In [[metazoan]]s the increase in the rate of histone synthesis is due to the increase in processing of pre-mRNA to its mature form as well as decrease in mRNA degradation; this results in an increase of active mRNA for translation of histone proteins. The mechanism for mRNA activation has been found to be the removal of a segment of the 3' end of the mRNA strand, and is dependent on association with stem-loop binding protein ([[SLBP]]).<ref>{{cite journal | vauthors = Dominski Z, Erkmann JA, Yang X, Sànchez R, Marzluff WF | title = A novel zinc finger protein is associated with U7 snRNP and interacts with the stem-loop binding protein in the histone pre-mRNP to stimulate 3'-end processing | journal = Genes & Development | volume = 16 | issue = 1 | pages = 58–71 | date = January 2002 | pmid = 11782445 | pmc = 155312 | doi = 10.1101/gad.932302 }}</ref> SLBP also stabilizes histone mRNAs during S phase by blocking degradation by the 3'hExo nuclease.<ref>{{cite journal | vauthors = Dominski Z, Yang XC, Kaygun H, Dadlez M, Marzluff WF | title = A 3' exonuclease that specifically interacts with the 3' end of histone mRNA | journal = Molecular Cell | volume = 12 | issue = 2 | pages = 295–305 | date = August 2003 | pmid = 14536070 | doi = 10.1016/S1097-2765(03)00278-8 | doi-access = free }}</ref> SLBP levels are controlled by cell-cycle proteins, causing SLBP to accumulate as cells enter S phase and degrade as cells leave S phase. SLBP are marked for degradation by phosphorylation at two threonine residues by cyclin dependent kinases, possibly cyclin A/ cdk2, at the end of S phase.<ref>{{cite journal | vauthors = Zheng L, Dominski Z, Yang XC, Elms P, Raska CS, Borchers CH, Marzluff WF | title = Phosphorylation of stem-loop binding protein (SLBP) on two threonines triggers degradation of SLBP, the sole cell cycle-regulated factor required for regulation of histone mRNA processing, at the end of S phase | journal = Molecular and Cellular Biology | volume = 23 | issue = 5 | pages = 1590–601 | date = March 2003 | pmid = 12588979 | pmc = 151715 | doi = 10.1128/MCB.23.5.1590-1601.2003 }}</ref>  Metazoans also have multiple copies of histone genes clustered on chromosomes which are localized in structures called Cajal bodies as determined by genome-wide chromosome conformation capture analysis (4C-Seq).<ref>{{cite journal | vauthors = Wang Q, Sawyer IA, Sung MH, Sturgill D, Shevtsov SP, Pegoraro G, Hakim O, Baek S, Hager GL, Dundr M | title = Cajal bodies are linked to genome conformation | journal = Nature Communications | volume = 7 | pages = 10966 | date = March 2016 | pmid = 26997247 | pmc = 4802181 | doi = 10.1038/ncomms10966 | bibcode = 2016NatCo...710966W }}</ref>