Kinetochore protein Cnn1 promotes sister chromatid bi-orientation by modulating intraKMN affinities in a biphasic, phospho-regulated manner.

Kinetochores are large proteinaceous structures that assemble on centromeres to align sister chromatids to the mitotic spindle and orchestrate their segregation to the daughter cells. At the core of kinetochores lies a network of proteins known as KMN, whose microtubule-binding activity is regulated by the Ipl1/Aurora B and Mps1 kinases. Here, we have characterized a novel structural yeast kinetochore protein named Cnn1 and show that it regulates KMN-spindle activity by modulating the affinity between the KMN subcomplexes at their basis. Cnn1 supports KMN from S phase to anaphase, and is controlled by the Cdc28, Mps1 and Ipl1 kinases. Cnn1 has evolved to associate the KMN complexes into a coherent network activity to ensure efficient S.cerevisiae oligonucleotide microarrays were provided by Affymetrix (S.cerevisiae Tiling 1.0R, P/N 900645). ChIP-chip analyses were carried out as described (Bermejo et al., Cell, 2009).

动粒（kinetochores）是一类大型蛋白质复合物，组装于着丝粒（centromeres）之上，负责将姐妹染色单体锚定至有丝分裂纺锤体，并协调其向子代细胞的分离。动粒的核心是一套被称为KMN的蛋白质网络，其微管结合活性受Ipl1/极光激酶B（Aurora B）与Mps1激酶的调控。本研究对一种全新的酿酒酵母（S.cerevisiae）动粒结构蛋白Cnn1进行了表征，结果显示其通过调节KMN亚复合物核心区域之间的结合亲和力，调控KMN-纺锤体的活性。Cnn1在S期至有丝分裂后期均维持KMN的功能，并受Cdc28、Mps1及Ipl1激酶的调控。Cnn1经进化将KMN复合物整合为连贯的网络活性，以保障高效的染色体分离过程。酿酒酵母寡核苷酸微阵列由Affymetrix公司提供（酿酒酵母平铺芯片1.0R，货号900645）。染色质免疫共沉淀芯片（ChIP-chip）分析按照已发表方法进行（Bermejo等人，《细胞》，2009年）。