The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, 2200 Copenhagen, Denmark.
J Cell Sci. 2013 Mar 1;126(Pt 5):1086-92. doi: 10.1242/jcs.122481. Epub 2013 Jan 23.
BubR1 is a central component of the spindle assembly checkpoint that inhibits progression into anaphase in response to improper kinetochore-microtubule interactions. In addition, BubR1 also helps stabilize kinetochore-microtubule interactions by counteracting the Aurora B kinase but the mechanism behind this is not clear. Here we show that BubR1 directly binds to the B56 family of protein phosphatase 2A (PP2A) regulatory subunits through a conserved motif that is phosphorylated by cyclin-dependent kinase 1 (Cdk1) and polo-like kinase 1 (Plk1). Two highly conserved hydrophobic residues surrounding the serine 670 Cdk1 phosphorylation site are required for B56 binding. Mutation of these residues prevents the establishment of a proper metaphase plate and delays cells in mitosis. Furthermore, we show that phosphorylation of serines 670 and 676 stimulates the binding of B56 to BubR1 and that BubR1 targets a pool of B56 to kinetochores. Our data suggest that BubR1 counteracts Aurora B kinase activity at improperly attached kinetochores by recruiting B56-PP2A phosphatase complexes.
BubR1 是纺锤体组装检查点的核心组成部分，它可以抑制因动粒微管结合异常而进入后期。此外，BubR1 还可以通过拮抗 Aurora B 激酶来稳定动粒微管的相互作用，但这背后的机制尚不清楚。在这里，我们发现 BubR1 通过一个由 cyclin-dependent kinase 1（Cdk1）和 polo-like kinase 1（Plk1）磷酸化的保守基序，直接与 B56 家族的蛋白磷酸酶 2A（PP2A）调节亚基结合。位于丝氨酸 670 Cdk1 磷酸化位点周围的两个高度保守的疏水性残基对于 B56 结合是必需的。这些残基的突变会阻止形成正确的中期板并使细胞在有丝分裂中延迟。此外，我们发现丝氨酸 670 和 676 的磷酸化可以刺激 B56 与 BubR1 的结合，并且 BubR1 将一组 B56 靶向到动粒上。我们的数据表明，BubR1 通过招募 B56-PP2A 磷酸酶复合物来拮抗 Aurora B 激酶在不正确连接的动粒上的活性。
