Horlbeck et al, eLIFE (2016), 10.7554/eLife.12677, http://www.ncbi.nlm.nih.gov/pubmed/26987018
While research has focused on decreasing off-target effects, little work has been done on analyzing Cas9’s activity in different parts of the genome. In order to understand how nucleosomes affect Cas9’s ability to access genomic DNA Horlbeck et al. performed a large scale genomic screen targeting areas both with and without nucleosomes. This screen found low levels of Cas9 activity in nucleosome enriched regions with chromatin remodeling restoring Cas9 activity in these regions. This research will allow CRISPR/Cas9 users to better predict guide activity in vivo.