EMD-9655
Cryo-EM structure of type III-A Csm complex
EMD-9655
Single-particle3.8 Å
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Map released: 12/12/2018
Last modified: 30/01/2019
Sample Organism:
Streptococcus thermophilus ND03
Sample: Csm-CTR1 complex, AMPPNP bound
Deposition Authors: You L, Ma J, Wang J, Zhang X, Wang Y
Sample: Csm-CTR1 complex, AMPPNP bound
Deposition Authors: You L, Ma J, Wang J, Zhang X, Wang Y
Structure Studies of the CRISPR-Csm Complex Reveal Mechanism of Co-transcriptional Interference
You L,
Ma J
,
Wang J,
Artamonova D
,
Wang M,
Liu L
,
Xiang H,
Severinov K,
Zhang X,
Wang Y
(2019) Cell , 176 , 239 - 253.e16
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(2019) Cell , 176 , 239 - 253.e16
Abstract:
Csm, a type III-A CRISPR-Cas interference complex, is a CRISPR RNA (crRNA)-guided RNase that also possesses target RNA-dependent DNase and cyclic oligoadenylate (cOA) synthetase activities. However, the structural features allowing target RNA-binding-dependent activation of DNA cleavage and cOA generation remain unknown. Here, we report the structure of Csm in complex with crRNA together with structures of cognate or non-cognate target RNA bound Csm complexes. We show that depending on complementarity with the 5' tag of crRNA, the 3' anti-tag region of target RNA binds at two distinct sites of the Csm complex. Importantly, the interaction between the non-complementary anti-tag region of cognate target RNA and Csm1 induces a conformational change at the Csm1 subunit that allosterically activates DNA cleavage and cOA generation. Together, our structural studies provide crucial insights into the mechanistic processes required for crRNA-meditated sequence-specific RNA cleavage, RNA target-dependent non-specific DNA cleavage, and cOA generation.
Csm, a type III-A CRISPR-Cas interference complex, is a CRISPR RNA (crRNA)-guided RNase that also possesses target RNA-dependent DNase and cyclic oligoadenylate (cOA) synthetase activities. However, the structural features allowing target RNA-binding-dependent activation of DNA cleavage and cOA generation remain unknown. Here, we report the structure of Csm in complex with crRNA together with structures of cognate or non-cognate target RNA bound Csm complexes. We show that depending on complementarity with the 5' tag of crRNA, the 3' anti-tag region of target RNA binds at two distinct sites of the Csm complex. Importantly, the interaction between the non-complementary anti-tag region of cognate target RNA and Csm1 induces a conformational change at the Csm1 subunit that allosterically activates DNA cleavage and cOA generation. Together, our structural studies provide crucial insights into the mechanistic processes required for crRNA-meditated sequence-specific RNA cleavage, RNA target-dependent non-specific DNA cleavage, and cOA generation.