Journal
CELL
Volume 163, Issue 4, Pages 854-865Publisher
CELL PRESS
DOI: 10.1016/j.cell.2015.10.003
Keywords
-
Categories
Funding
- NSF
- National Defense Science & Engineering Graduate Research Fellowship programs
- NIH [GM074739, GM108888]
- HHMI Early Career Scientist Award
- NSF [MCB-1154511, MCB-1244557]
- Div Of Molecular and Cellular Bioscience
- Direct For Biological Sciences [1154511] Funding Source: National Science Foundation
Ask authors/readers for more resources
CRISPR-Cas adaptive immune systems protect bacteria and archaea against foreign genetic elements. In Escherichia coli, Cascade (CRISPR-associated complex for antiviral defense) is an RNA-guided surveillance complex that binds foreign DNA and recruits Cas3, a trans-acting nuclease helicase for target degradation. Here, we use single-molecule imaging to visualize Cascade and Cas3 binding to foreign DNA targets. Our analysis reveals two distinct pathways dictated by the presence or absence of a protospacer-adjacent motif (PAM). Binding to a protospacer flanked by a PAM recruits a nuclease-active Cas3 for degradation of short single-stranded regions of target DNA, whereas PAM mutations elicit an alternative pathway that recruits a nuclease-inactive Cas3 through a mechanism that is dependent on the Cas1 and Cas2 proteins. These findings explain how target recognition by Cascade can elicit distinct outcomes and support a model for acquisition of new spacer sequences through a mechanism involving processive, ATP-dependent Cas3 translocation along foreign DNA.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available