Foreign DNA capture during CRISPR-Cas adaptive immunity.
Nature
; 527(7579): 535-8, 2015 Nov 26.
Article
em En
| MEDLINE
| ID: mdl-26503043
ABSTRACT
Bacteria and archaea generate adaptive immunity against phages and plasmids by integrating foreign DNA of specific 30-40-base-pair lengths into clustered regularly interspaced short palindromic repeat (CRISPR) loci as spacer segments. The universally conserved Cas1-Cas2 integrase complex catalyses spacer acquisition using a direct nucleophilic integration mechanism similar to retroviral integrases and transposases. How the Cas1-Cas2 complex selects foreign DNA substrates for integration remains unknown. Here we present X-ray crystal structures of the Escherichia coli Cas1-Cas2 complex bound to cognate 33-nucleotide protospacer DNA substrates. The protein complex creates a curved binding surface spanning the length of the DNA and splays the ends of the protospacer to allow each terminal nucleophilic 3'-OH to enter a channel leading into the Cas1 active sites. Phosphodiester backbone interactions between the protospacer and the proteins explain the sequence-nonspecific substrate selection observed in vivo. Our results uncover the structural basis for foreign DNA capture and the mechanism by which Cas1-Cas2 functions as a molecular ruler to dictate the sequence architecture of CRISPR loci.
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Base de dados:
MEDLINE
Assunto principal:
DNA Viral
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Integração Viral
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Imunidade Adaptativa
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Proteínas Associadas a CRISPR
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Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas
Idioma:
En
Ano de publicação:
2015
Tipo de documento:
Article