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RNA Targeting by the Type III-A CRISPR-Cas Csm Complex of Thermus thermophilus

  • Author(s): Staals, RHJ
  • Zhu, Y
  • Taylor, DW
  • Kornfeld, JE
  • Sharma, K
  • Barendregt, A
  • Koehorst, JJ
  • Vlot, M
  • Neupane, N
  • Varossieau, K
  • Sakamoto, K
  • Suzuki, T
  • Dohmae, N
  • Yokoyama, S
  • Schaap, PJ
  • Urlaub, H
  • Heck, AJR
  • Nogales, E
  • Doudna, JA
  • Shinkai, A
  • vanderOost, J
  • et al.

Published Web Location

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4342149/
No data is associated with this publication.
Abstract

© 2014 Elsevier Inc. CRISPR-Cas is a prokaryotic adaptive immune system that provides sequence-specific defense against foreign nucleic acids. Here we report the structure and function of the effector complex of the Type III-A CRISPR-Cas system of Thermus thermophilus: the Csm complex (TtCsm). TtCsm is composed of five different protein subunits (Csm1-Csm5) with an uneven stoichiometry and a single crRNA of variable size (35-53 nt). The TtCsm crRNA content is similar to the Type III-B Cmr complex, indicating that crRNAs are shared among different subtypes. A negative stain EM structure of the TtCsm complex exhibits the characteristic architecture of Type I and Type III CRISPR-associated ribonucleoprotein complexes. crRNA-protein crosslinking studies show extensive contacts between the Csm3 backbone and the bound crRNA. We show that, like TtCmr, TtCsm cleaves complementary target RNAs at multiple sites. Unlike Type I complexes, interference by TtCsm does not proceed via initial base pairing by a seed sequence.

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