Surveillance and Processing of Foreign DNA by the Escherichia coli CRISPR-Cas System.
Cell
; 163(4): 854-65, 2015 Nov 05.
Article
en 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
Banco de datos:
MEDLINE
Asunto principal:
ADN Viral
/
Bacteriófago lambda
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ADN Helicasas
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Proteínas de Escherichia coli
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Endodesoxirribonucleasas
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Endonucleasas
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Escherichia coli
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Proteínas Asociadas a CRISPR
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Sistemas CRISPR-Cas
Tipo de estudio:
Prognostic_studies
/
Screening_studies
Idioma:
En
Año:
2015
Tipo del documento:
Article