Representative structure of Cas proteins with effector proteins. Class I Cascade complex fused to an effector domain (A) and Class II catalytically inactive Cas protein fused to an effector domain (B) are shown. These engineered Cas proteins have been applied for transcriptional control, epigenetic modification, base editing, etc. at target sites. Effector domains can be fused to any Cas proteins of Cascade complex (A) whereas an effector domain can be fused to one Cas protein (B).