Editing Histone octamer (section)

===Nucleosome remodeling and disassembly===
{{Further|Chromatin remodeling}}
In order to access the nucleosomal DNA, the bonds between it and the histone octamer must be broken. This change takes place periodically in the cell as specific regions are transcribed, and it happens genome-wide during replication. Remodeling proteins work in three distinct ways: they can slide the DNA along the surface of the octamer, replace the one histone dimer with a variant, or remove the histone octamer entirely. No matter the method, in order to modify the nucleosomes, the remodeling complexes require energy from ATP hydrolysis to drive their actions.

Of the three techniques, sliding is the most common and least extreme.<ref>{{cite journal|last=Becker|first=P. B.|title=NEW EMBO MEMBER'S REVIEW: Nucleosome sliding: facts and fiction|journal=The EMBO Journal|date=16 September 2002|volume=21|issue=18|pages=4749–4753|doi=10.1093/emboj/cdf486|pmid=12234915|pmc=126283}}</ref>  The basic premise of the technique is to free up a region of DNA that the histone octamer would normally tightly bind. While the technique is not well defined, the most prominent hypothesis is that the sliding is done in an “inchworm” fashion. In this method, using ATP as an energy source, the translocase domain of the nucleosome-remodeling complex detaches a small region of DNA from the histone octamer. This “wave” of DNA, spontaneously breaking and remaking the hydrogen bonds as it goes, then propagates down the nucleosomal DNA until it reaches the last binding site with the histone octamer. Once the wave reaches the end of the histone octamer the excess that was once at the edge is extended into the region of linker DNA. In total, one round of this method moves the histone octamer several base pairs in a particular direction—away from the direction the “wave” propagated.<ref name=watson /><ref>{{cite journal|last=Fazzio|first=TG|author2=Tsukiyama, T|title=Chromatin remodeling in vivo: evidence for a nucleosome sliding mechanism.|journal=Molecular Cell|date=November 2003|volume=12|issue=5|pages=1333–40|pmid=14636590|doi=10.1016/s1097-2765(03)00436-2|doi-access=free}}</ref>