6O1O

Cryo-EM structure of the T. thermophilus Csm complex bound to target ssRNA

Summary for 6O1O

• Entry DOI: 10.2210/pdb6o1o/pdb
• EMDB information: 0454
• Descriptor: Csm1, Csm4, Csm3, ... (6 entities in total)
• Functional Keywords: csm, rna substrate, rna binding protein, rna binding protein-rna complex, rna binding protein/rna
• Biological source: Thermus thermophilus; More
• Total number of polymer chains: 14
• Total formula weight: 278297.24

Authors

Liu, J.J.,Liu, T.Y. (deposition date: 2019-02-21, release date: 2019-07-10, Last modification date: 2024-03-13)

Primary citation

Liu, T.Y.,Liu, J.J.,Aditham, A.J.,Nogales, E.,Doudna, J.A.
Target preference of Type III-A CRISPR-Cas complexes at the transcription bubble.
Nat Commun, 10:3001-3001, 2019

PubMed Abstract: Type III-A CRISPR-Cas systems are prokaryotic RNA-guided adaptive immune systems that use a protein-RNA complex, Csm, for transcription-dependent immunity against foreign DNA. Csm can cleave RNA and single-stranded DNA (ssDNA), but whether it targets one or both nucleic acids during transcription elongation is unknown. Here, we show that binding of a Thermus thermophilus (T. thermophilus) Csm (TthCsm) to a nascent transcript in a transcription elongation complex (TEC) promotes tethering but not direct contact of TthCsm with RNA polymerase (RNAP). Biochemical experiments show that both TthCsm and Staphylococcus epidermidis (S. epidermidis) Csm (SepCsm) cleave RNA transcripts, but not ssDNA, at the transcription bubble. Taken together, these results suggest that Type III systems primarily target transcripts, instead of unwound ssDNA in TECs, for immunity against double-stranded DNA (dsDNA) phages and plasmids. This reveals similarities between Csm and eukaryotic RNA interference, which also uses RNA-guided RNA targeting to silence actively transcribed genes.

PubMed: 31278272
DOI: 10.1038/s41467-019-10780-2

Experimental method

ELECTRON MICROSCOPY (3.8 Å)