Editing Nucleosome (section)

=== DNA Twist Defects ===
DNA twist defects are when the addition of one or a few base pairs from one DNA segment are transferred to the next segment resulting in a change of the DNA twist. This will not only change the twist of the DNA but it will also change the length.<ref>{{cite journal | vauthors = Winger J, Nodelman IM, Levendosky RF, Bowman GD | title = A twist defect mechanism for ATP-dependent translocation of nucleosomal DNA | journal = eLife | volume = 7 | pages = e34100 | date = May 2018 | pmid = 29809147 | pmc = 6031429 | doi = 10.7554/eLife.34100 | doi-access = free }}</ref> This twist defect eventually moves around the nucleosome through the transferring of the base pair, this means DNA twists can cause nucleosome sliding.<ref>{{cite journal | vauthors = Bowman GD | title = Uncovering a New Step in Sliding Nucleosomes | journal = Trends in Biochemical Sciences | volume = 44 | issue = 8 | pages = 643–645 | date = August 2019 | pmid = 31171402 | pmc = 7092708 | doi = 10.1016/j.tibs.2019.05.001 }}</ref> Nucleosome crystal structures have shown that superhelix location 2 and 5 on the nucleosome are commonly found to be where DNA twist defects occur as these are common remodeler binding sites.<ref name=":0">{{cite journal | vauthors = Nodelman IM, Bowman GD | title = Biophysics of Chromatin Remodeling | journal = Annual Review of Biophysics | volume = 50 | issue = 1 | pages = 73–93 | date = May 2021 | pmid = 33395550 | pmc = 8428145 | doi = 10.1146/annurev-biophys-082520-080201 }}</ref> There are a variety of chromatin remodelers but all share the existence of an ATPase motor which facilitates chromatin sliding on DNA through the binding and hydrolysis of ATP.<ref name=":1">{{cite journal | vauthors = Brandani GB, Takada S | title = Chromatin remodelers couple inchworm motion with twist-defect formation to slide nucleosomal DNA | journal = PLOS Computational Biology | volume = 14 | issue = 11 | pages = e1006512 | date = November 2018 | pmid = 30395604 | pmc = 6237416 | doi = 10.1371/journal.pcbi.1006512 | bibcode = 2018PLSCB..14E6512B | veditors = Onufriev A | doi-access = free }}</ref> ATPase has an open and closed state. When the ATPase motor is changing from open and closed states, the DNA duplex changes geometry and exhibits base pair tilting.<ref name=":0" /> The initiation of the twist defects via the ATPase motor causes tension to accumulate around the remodeler site. The tension is released when the sliding of DNA has been completed throughout the nucleosome via the spread of two twist defects (one on each strand) in opposite directions.<ref name=":1" />