Editing Nucleosome (section)

=== Nucleosome free region ===
Promoters of active genes have nucleosome free regions (NFR). This allows for promoter DNA accessibility to various proteins, such as transcription factors. Nucleosome free region typically spans for 200 nucleotides in ''S. cerevisiae''<ref>{{cite journal | vauthors = Yuan GC, Liu YJ, Dion MF, Slack MD, Wu LF, Altschuler SJ, Rando OJ | title = Genome-scale identification of nucleosome positions in S. cerevisiae | journal = Science | volume = 309 | issue = 5734 | pages = 626–630 | date = July 2005 | pmid = 15961632 | doi = 10.1126/science.1112178 | s2cid = 43625066 | bibcode = 2005Sci...309..626Y | doi-access = free }}</ref> Well-positioned nucleosomes form boundaries of NFR. These nucleosomes are called +1-nucleosome and −1-nucleosome and are located at canonical distances downstream and upstream, respectively, from transcription start site.<ref name="Understanding nucleosome dynamics">{{cite journal | vauthors = Lai WK, Pugh BF | title = Understanding nucleosome dynamics and their links to gene expression and DNA replication | journal = Nature Reviews. Molecular Cell Biology | volume = 18 | issue = 9 | pages = 548–562 | date = September 2017 | pmid = 28537572 | pmc = 5831138 | doi = 10.1038/nrm.2017.47 }}</ref> +1-nucleosome and several downstream nucleosomes also tend to incorporate H2A.Z histone variant.<ref name="Understanding nucleosome dynamics"/>