如何通过Cas1-Cas2介导间隔器集成来建立CRISPR-Cas类型II免疫力
Yibei Xiao1, Sherwin Ng1, Ki Hyun Nam2
1Department of Molecular Biology and Genetics, Cornell University, 253 Biotechnology Building, Ithaca, New York 14853, USA.
Nature
|September 5, 2017
概括
CRISPR-Cas系统使用Cas1-Cas2蛋白质将外来DNA间隔器集成到CRISPR阵列中,形成适应性免疫. 这项研究揭示了Enterococcus faecalis中间隔器集成的逐步机制,突出了DNA曲和领导近位偏好.
科学领域:
- 微生物学
- 分子生物学
- 遗传学
背景情况:
- CRISPR-Cas系统提供了以RNA为导向的适应性免疫力来对抗外来遗传元素.
- 间隔器融合,即将外来DNA纳入CRISPR阵列的过程,是适应性免疫所必需的保存机制.
- 虽然一般的机制是已知的,但在间隔器集成期间的精确分子事件和蛋白质相互作用在不同的CRISPR- Cas类型中有所不同.
研究的目的:
- 在Enterococcus faecalis的II-ACRISPR-Cas系统中阐明由Cas1-Cas2复合体介导的间隔器集成的结构和机制细节.
- 在关键集成步骤中提供Cas1-Cas2预测器复合物的高分辨率结构快照.
- 开发一个机制框架来解释观察到的领导者与邻近的整合偏好.
主要方法:
- 纯化和结构分析Enterococcus faecalis Cas1-Cas2复合体与一个预空间DNA结合.
- 时间解决的结构研究,捕捉间隔器集成过程的中间状态.
- 生物化学测试以调查蛋白质-DNA相互作用和催化活性.
主要成果:
- Enterococcus faecalis Cas1-Cas2 复合体选择性地与特定的3' 突起结合了扩散的 DNA 预位器.
- 结构快照显示了三步的过程:随机半位点搜索,首选绑定到领先的近邻CRISPR重复,以及核友攻击进行整合.
- DNA 曲对于识别间隔器半位点至关重要,从而使预间隔器完全集成到 CRISPR 阵列中.
结论:
- 该研究提供了由Cas1-Cas2整合酶复合体驱动的II-ACRISPR间隔器集成的详细机制模型.
- 这些发现突显了DNA构成和特定蛋白质-DNA相互作用在指导新间隔器的优先,近位集成方面的重要性.
- 这项工作加深了我们对基于CRISPR的适应性免疫的基本分子机制的理解.
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