GEN News Highlights, 29 December 2016, http://www.genengnews.com/gen-news-highlights/off-switch-found-for-common-version-of-the-crispr-cas9-system/81253625
A new Cell publication (http://www.cell.com/cell/abstract/S0092-8674(16)31683-X) has demonstrated a CRISPR off switch by studying self-targeting bacteria—bacteria where viruses defeated CRISPR and integrated into the bacterial genome. In these self-targeting bacteria, viral DNA can be found at both the CRISPR locus and in additional locations within the genome. The authors hypothesized that the virus had a method to deactivate the CRISPR mechanism, preventing the CRISPR system from cutting the integrated viral DNA, killing the bacterium itself. Four CRISPR/Cas9 inhibitor proteins were discovered in the Listeria monocytogenes prophages, allowing for the potential use of these inhibitors in CRISPR gene editing experiments.