Ipl1-dependent phosphorylation of Dam1 is reduced by tension applied on kinetochores
Ipl1-dependent phosphorylation of Dam1 is reduced by tension applied on kinetochores
复制标题
DOI：
10.1242/jcs.055566
复制
发表时间：
2009-12-01
影响因子：
4
通讯作者：
Stark, Michael J. R.
中科院分区：
文献类型：
--
作者：
Keating, Patrick;Rachidi, Najma;Stark, Michael J. R.
保守的极光B蛋白激酶（Ipl 1在酿酒酵母）是必不可少的，以确保姐妹着丝粒成为连接到微管从相反的纺锤体两极（双向）在后期开始。当姐妹染色单体从一个单极附着到微管上时，Aurora B/Ipl 1促进了着丝粒-微管附着的周转。这一过程需要极光B/Ipl 1对动粒组分如酵母中的Dam 1进行磷酸化。一旦双向定位建立，张力作用于动粒，Aurora B/Ipl 1必须停止促进这种转换，否则正确的附着将永远不会稳定。这是如何实现的仍然是难以捉摸的：它可能是由于极光B/Ipl 1底物在动粒的去磷酸化，或可能独立发生，例如，由于动粒的构象变化。在这里，我们表明，Ipl 1依赖的磷酸化在Dam 1的关键位点是最大的S期和最小的中期，染色体双方向发生时，匹配的细胞周期窗口。有趣的是，当我们通过未能建立姐妹染色单体凝聚力来降低着丝粒的张力时，Dam 1磷酸化在中期阻滞的细胞中持续存在。我们建议，极光B/Ipl 1促进的双向取向是稳定的张力在着丝粒的Dam 1的去磷酸化，导致终止着丝粒微管附着营业额。
The conserved Aurora B protein kinase (Ipl1 in Saccharomyces cerevisiae) is essential for ensuring that sister kinetochores become attached to microtubules from opposite spindle poles (bi-orientation) before anaphase onset. When sister chromatids become attached to microtubules from a single pole, Aurora B/Ipl1 facilitates turnover of kinetochore-microtubule attachments. This process requires phosphorylation by Aurora B/Ipl1 of kinetochore components such as Dam1 in yeast. Once bi-orientation is established and tension is applied on kinetochores, Aurora B/Ipl1 must stop promoting this turnover, otherwise correct attachment would never be stabilised. How this is achieved remains elusive: it might be due to dephosphorylation of Aurora B/Ipl1 substrates at kinetochores, or might take place independently, for example because of conformational changes in kinetochores. Here, we show that Ipl1-dependent phosphorylation at crucial sites on Dam1 is maximal during S phase and minimal during metaphase, matching the cell cycle window when chromosome bi-orientation occurs. Intriguingly, when we reduced tension at kinetochores through failure to establish sister chromatid cohesion, Dam1 phosphorylation persisted in metaphase-arrested cells. We propose that Aurora B/Ipl1-facilitated bi-orientation is stabilised in response to tension at kinetochores by dephosphorylation of Dam1, resulting in termination of kinetochore-microtubule attachment turnover.