Structure basis for RNA-guided DNA degradation by Cascade and Cas3.
Science
; 361(6397)2018 07 06.
Article
en En
| MEDLINE
| ID: mdl-29880725
ABSTRACT
Type I CRISPR-Cas system features a sequential target-searching and degradation process on double-stranded DNA by the RNA-guided Cascade (CRISPR associated complex for antiviral defense) complex and the nuclease-helicase fusion enzyme Cas3, respectively. Here, we present a 3.7-angstrom-resolution cryo-electron microscopy (cryo-EM) structure of the Type I-E Cascade/R-loop/Cas3 complex, poised to initiate DNA degradation. Cas3 distinguishes Cascade conformations and only captures the R-loop-forming Cascade, to avoid cleaving partially complementary targets. Its nuclease domain recruits the nontarget strand (NTS) DNA at a bulged region for the nicking of single-stranded DNA. An additional 4.7-angstrom-resolution cryo-EM structure captures the postnicking state, in which the severed NTS retracts to the helicase entrance, to be threaded for adenosine 5'-triphosphate-dependent processive degradation. These snapshots form the basis for understanding RNA-guided DNA degradation in Type I-E CRISPR-Cas systems.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Proteínas Bacterianas
/
ADN
/
Actinobacteria
/
ARN Guía de Kinetoplastida
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ADN Helicasas
/
Roturas del ADN de Cadena Simple
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Fragmentación del ADN
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Proteínas Asociadas a CRISPR
Idioma:
En
Revista:
Science
Año:
2018
Tipo del documento:
Article
País de afiliación:
Estados Unidos