The unstable F-box protein p58-Ctf13 forms the structural core of the CBF3 kinetochore complex
The unstable F-box protein p58-Ctf13 forms the structural core of the CBF3 kinetochore complex
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DOI：
10.1083/jcb.145.5.933
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发表时间：
1999-05-31
影响因子：
7.8
通讯作者：
Sorger, PK
中科院分区：
文献类型：
--
作者：
Russell, ID;Grancell, AS;Sorger, PK
动粒在芽殖酵母中比在其他任何真核生物中更小，也更容易通过实验获得。相信简单和复杂的动粒具有重要的结构和功能特性的共同点，我们的特点是CBF3，启动动粒形成在酿酒酵母中的基本着丝粒结合复合物的结构。我们发现CBF3的四个亚基在溶液中是多聚体：p23（Skp1）和p58（Ctf13）形成异源二聚体，p64（Cep3）和p110（Ndc10）形成同源二聚体。涉及p58和其他CBF3亚基的亚复合物可以在没有着丝粒DNA的情况下组装。在这些亚复合物中，p58似乎起着介导其他CBF3蛋白之间稳定相互作用的结构核心的作用，p58在酵母中具有短的半衰期，受到泛素依赖性蛋白水解的影响，但我们发现它在与p64结合后更加稳定。我们认为p23（Skp1）-p58-p64复合物构成了酵母细胞中活性p58的主要库。这些复合物可以解离，使p58重新暴露于降解途径，或者可以结合p110和着丝粒DNA，形成功能性CBF3复合物，其中p58被完全保护免于降解。该途径可能构成一种编辑机制，防止异位动粒的形成并确保染色体分离的保真度。
Kinetochores are smaller and more accessible experimentally in budding yeast than in any other eukaryote. Believing that simple and complex kinetochores have important structural and functional properties in common, we characterized the structure of CBF3, the essential centromere-binding complex that initiates kinetochore formation in Saccharomyces cerevisiae. We find that the four subunits of CBF3 are multimeric in solution: p23(Skp1) and p58(Ctf13) form a heterodimer, and p64(Cep3) and p110(Ndc10) form homodimers. Subcomplexes involving p58 and each of the other CBF3 subunits can assemble in the absence of centromeric DNA. In these subcomplexes, p58 appears to function as a structural core mediating stable interactions among other CBF3 proteins, p58 has a short half-life in yeast, being subject to ubiquitin-dependent proteolysis, but we find that it is much more stable following association with p64. We propose that p23(Skp1)-p58-p64 complexes constitute the primary pool of active p58 in yeast cells. These complexes can either dissociate, reexposing p58 to the degradation pathway, or can bind to p110 and centromeric DNA, forming a functional CBF3 complex in which p58 is fully protected from degradation. This pathway may constitute an editing mechanism preventing the formation of ectopic kinetochores and ensuring the fidelity of chromosome segregation.