复制起源的机制 化由CMG螺旋酶组合核化
Jacob S Lewis1, Marta H Gross2, Joana Sousa1,3
1Macromolecular Machines Laboratory, The Francis Crick Institute, London, UK.
Nature
|June 15, 2022
概括
细胞DNA复制的启动包括形成Cdc45-MCM-GINS (CMG) 全螺旋酶,通过解双螺旋和破碎基对来溶解DNA,确保稳定的复制分叉的建立.
科学领域:
- 分子生物学
- 细胞生物学
- 生物化学
背景情况:
- 细胞DNA复制需要精确,及时的原始激活以防止重复复制.
- MCM螺旋酶加载是一个早期的步骤,其次是引燃因子的招募,以形成CMG全螺旋酶.
- 在复制起源的CMG组装过程中DNA化的机制尚不清楚.
研究的目的:
- 阐明依赖ATP的CMG组合和DNA化的结构机制.
- 研究CMG形成在破坏MCM双六合体和启动DNA解中的作用.
- 确定特定的MCM残留在DNA解和复制促进中的作用.
主要方法:
- 使用冷电子显微镜 (cryo-EM) 可视化ATP依赖的CMG组件在复制的染色酵母来源.
- 使用纯化的酵母蛋白进行体外溶解,可进行详细的结构分析.
- 生物化学测试评估了特定的Mcm2孔环残留物的功能.
主要成果:
- CMG 形成破坏了 MCM 双六合体接口,暴露了两个绑定的 CMG 基酶之间的双重DNA,形成了分离的二合体.
- 在每个MCM环内,ATP结合会引发形状变化,从而解开DNA双螺旋并破坏基配对.
- 特定的Mcm2孔环残留物对于DNA解和促进复制至关重要,但对于初始的CMG形成是不可或缺的.
结论:
- 对CMG核酸的ATP结合导致DNA化,这是复制启动的关键步骤.
- 在源激活过程中,CMG的扩散二元结构有助于复制体的稳定性.
- 这项研究为了解如何激活复制起源和启动DNA解提供了结构基础.
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