Enhancing Cas9 Activity in Heterochromatin
Daer R, Barrett C, Haynes KA. (2017) bioRxiv. https://www.biorxiv.org/content/early/2017/12/04/228601
CRISPR is a powerful and popular tool for editing DNA in living cells. Scientists are becoming more interested in using CRISPR to correct mistakes in DNA that lead to diseases, to artificially generate mutations to research the origins of diseases, and for other important applications. However, CRISPR originated in bacteria and has probably not evolved to function very well in genomes that are packed in configurations (open and closed chromatin) as complex as those found in human cells. In a recent report (Daer et al. 2017), we demonstrated that CRISPR activity was inhibited at a DNA sequence that became artificially condensed into closed chromatin. Our new study shows that targeted re-opening of closed chromatin leads to enhanced CRISPR activity in the same region. The epigenetic drug we tested (UNC1999) was not sufficient to generate a transcriptionally active or CRISPR-accessible state. In contrast, strong direct activation with a DNA-binding p65 protein did enhance CRISPR accessibility. Importantly, we learned that a recovery period (following treatment with p65) is needed to generate the CRISPR-accessible state.