Abstract 1146 Investigating the functional impact of type I-E Cascade conformational dynamics

The type I-E Cascade effector identifies complementary DNA targets through formation of an R-loop. Upon R-loop formation, the helicase-nuclease Cas3 is recruited by the Cas8 subunit of Cascade, allowing processive DNA degradation of the non-target strand in the 3' to 5' direction during CRISPR interference. Cascade and Cas3 also combine with the Cas1-Cas2 complex to promote primed spacer acquisition. The conformation of Cascade has been hypothesized to dictate these two alternative activities. Crystal structures of Cascade bound to dsDNA have revealed the N-terminal domain of Cas8 in a “closed” and the C-terminal domain of Cas8 in a “locked” conformation.