The gRAMP CRISPR-Cas effector is an RNA endonuclease complexed with a caspase-like peptidase

Type III CRISPR-Cas immunity is widespread in prokaryotes and is generally mediated by multisubunit effector complexes. These complexes recognize complementary viral transcripts and can activate ancillary immune proteins. Here, we describe a type III-E effector from Candidatus “Scalindua brodae” (Sb-gRAMP), which is natively encoded by a...

Craspase is a CRISPR RNA-guided, RNA-activated protease

The CRISPR-Cas type III-E RNA-targeting effector complex gRAMP/Cas7-11 is associated with a caspase-like protein (TPR-CHAT/Csx29) to form Craspase (CRISPR-guided caspase). Here, we use cryo-electron microscopy snapshots of Craspase to explain its target RNA cleavage and protease activation mechanisms. Target-guide pairing extending into the 5...

RNA-targeting CRISPR–Cas systems

CRISPR–Cas is a widespread adaptive immune system in bacteria and archaea that protects against viral infection by targeting specific invading nucleic acid sequences. Whereas some CRISPR–Cas systems sense and cleave viral DNA, type III and type VI CRISPR–Cas systems sense RNA that results from viral transcription and perhaps invasion by RNA...