Summary information and primary citation
- PDB-id
-
6o1o;
DSSR-derived features in text and
JSON formats
- Class
- RNA binding protein-RNA
- Method
- cryo-EM (3.8 Å)
- Summary
- cryo-EM structure of the t. thermophilus csm complex
bound to target ssrna
- Reference
-
Liu TY, Liu JJ, Aditham AJ, Nogales E, Doudna JA (2019):
"Target
preference of Type III-A CRISPR-Cas complexes at the
transcription bubble." Nat Commun,
10, 3001. doi: 10.1038/s41467-019-10780-2.
- 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.
