期刊
NATURE
卷 527, 期 7579, 页码 535-+出版社
NATURE RESEARCH
DOI: 10.1038/nature15760
关键词
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资金
- UC Office of the President
- Multicampus Research Programs
- Program for Breakthrough Biomedical Research - Sandler Foundation
- US National Science Foundation [1244557]
- NIH [AI070042]
- US National Science Foundation Graduate Research Fellowships
- UC Berkeley Chancellor's Graduate Fellowship
- [MR-15-328599]
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(1-6). The universally conserved Cas1-Cas2 integrase complex catalyses spacer acquisition using a direct nucleophilic integration mechanism similar to retroviral integrases and transposases(7-13). 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(2-4). 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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