AcrVIB1 inhibits CRISPR-Cas13b immunity by promoting unproductive crRNA binding accessible to RNase attack

CRISPR-Cas systems are showing tremendous promise in therapeutic and sensing technologies and their control using anti-CRISPR proteins is an active area of research. In this work, Wandera, et al. in the Beisel lab have characterized the mechanism by which anti-CRISPR protein AcrVIB1 inhibits CRISPR-Cas13b activity. AcrVIB1 binds to Cas13b and changes its conformation so that that the subsequently bound crRNA is susceptible to RNase degradation. Crystal structures confirmed that AcrVIB1 binding changes Cas13b’s ability to close around and protect the crRNA. myTXTL was used to test the effects of mutations on Cas13b or the anti-CRISPR protein AcrVIB1 on their targeting or inhibitory activity, respectively and these tests helped support the author’s conclusions about how AcrVIB1 interacts with the Cas13b nuclease.