Structure of the CRISPR Interference Complex CSM Reveals Key Similarities with Cascade

• DOI: 10.1016/j.molcel.2013.08.020
• Publication Date: 2013-10-10T19:58:09Z
• Authors: Christophe Rouillon; Min Zhou; Jing Zhang; Argyris Politis; Victoria Beilsten...; Giuseppe Cannone; Shirley Graham; Carol V. Robinson; Laura Spagnolo; Malcolm F. White
• Keywords: Models, Molecular; Spectrometry, Mass, Electrospray Ionization; Protein Conformation; Clustered Regularly Interspaced Palindromic Repeats (CRISPR) system; Archaeal Proteins; CRISPR-Associated Proteins; CSM complex; RNA, Archaeal; Methylation; Article; Structure-Activity Relationship; 03 medical and health sciences; Clustered Regularly Interspaced Short Palindromic Repeats; Prokaryotes; Phosphorylation; Molecular Biology; 0303 health sciences; Cascade complex; Sequence Analysis, RNA; 500; High-Throughput Nucleotide Sequencing; Acetylation; Cell Biology; 3. Good health; Microscopy, Electron; Protein Subunits; Immune system; Sulfolobus solfataricus

The Clustered Regularly Interspaced Palindromic Repeats (CRISPR) system is an adaptive immune system in prokaryotes. Interference complexes encoded by CRISPR-associated (cas) genes utilize small RNAs for homology-directed detection and subsequent degradation of invading genetic elements, and they have been classified into three main types (I-III). Type III complexes share the Cas10 subunit but are subclassifed as type IIIA (CSM) and type IIIB (CMR), depending on their specificity for DNA or RNA targets, respectively. The role of CSM in limiting the spread of conjugative plasmids in Staphylococcus epidermidis was first described in 2008. Here, we report a detailed investigation of the composition and structure of the CSM complex from the archaeon Sulfolobus solfataricus, using a combination of electron microscopy, mass spectrometry, and deep sequencing. This reveals a three-dimensional model for the CSM complex that includes a helical component strikingly reminiscent of the backbone structure of the type I (Cascade) family.