Liu, K. I. et. al. (2016) Nature Chemical Biology https://www.ncbi.nlm.nih.gov/pubmed/27618190
While CRISPR/Cas9 gene editing has become a versatile tool, inducible systems have continued to rely on transcriptional activation. While inducible promoters are a valuable research tool they can be slow to respond, creating a lag between induction and gene editing. To overcome this, Liu et. al. have developed a Cas9 variant fused to the hormone-binding domain of the estrogen receptor ERT2. This new Cas9 fusion, coined iCas, is rapidly activated by 4-hydroxytamoxifen (4-HT) treatment and demonstrates low endonuclease activity without 4-HT providing for a rapid and reversible Cas9 system.