Surveillance and Processing of Foreign DNA by the Escherichia coli CRISPR-Cas System.
Cell
; 163(4): 854-65, 2015 Nov 05.
Article
em En
| MEDLINE
| ID: mdl-26522594
ABSTRACT
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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
DNA Viral
/
Bacteriófago lambda
/
DNA Helicases
/
Proteínas de Escherichia coli
/
Endodesoxirribonucleases
/
Endonucleases
/
Escherichia coli
/
Proteínas Associadas a CRISPR
/
Sistemas CRISPR-Cas
Tipo de estudo:
Prognostic_studies
/
Screening_studies
Idioma:
En
Revista:
Cell
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Estados Unidos