Effects of phosphatase and proteasome inhibitors on Borealin phosphorylation and degradation
Effects of phosphatase and proteasome inhibitors on Borealin phosphorylation and degradation
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DOI：
10.1093/jb/mvs015
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发表时间：
2012-04-01
影响因子：
2.7
通讯作者：
Taylor, William R.
中科院分区：
文献类型：
--
作者：
Date, Dipali;Dreier, Megan R.;Taylor, William R.
染色体乘客复合物（CPC）的感觉张力缺陷的动粒激活纺锤体组装检查点，并帮助定位卵裂沟。CPC由INCENP、Survivin、Borealin和Aurora B组成，在中期定位于内着丝粒，在后期重新定位于纺锤体中间区; CPC的几种功能受翻译后修饰的调节。Borealin在多个位点磷酸化，S219的磷酸化导致Borealin在电泳时迁移更慢。在这里，我们发现Cdk 1可以诱导Borealin迁移率的变化，表明S219磷酸化是Cdk 1控制下。然而，Cdk 1在体外磷酸化纯化的Borealin是低效的。Borealin的酵母直向同源物Npl 1被磷酸酶Cdc 14去磷酸化。我们发现在缺乏Cdc 14 A或Cdc 14 B的人类细胞中Borealin的迁移率变化没有差异。相比之下，磷酸酶抑制剂冈田酸在细胞退出有丝分裂时确实延迟了Borealin的去磷酸化。蛋白酶体抑制剂MG 132减少有丝分裂中的Borealin磷酸化并增加Borealin的稳态水平，特别是在缺乏C-末端的突变体中。然而，第二个，结构无关的蛋白酶体抑制剂，lactacystin没有上调Borealin。这些结果表明，MG 132对Borealin的作用是由于抑制了除蛋白酶体以外的细胞内蛋白酶。
The chromosomal passenger complex (CPC) senses tension defects at the kinetochore to activate the spindle assembly checkpoint, and helps to position the cleavage furrow. The CPC, consisting of INCENP, Survivin, Borealin and Aurora B localizes to the inner centromere at metaphase and re-localizes to the spindle midzone at anaphase; several CPC functions are regulated by post-translational modification. Borealin is phosphorylated at multiple sites and phosphorylation at S219 causes Borealin to migrate more slowly upon electrophoresis. Here we find that Cdk1 can induce a mobility shift of Borealin, suggesting that S219 phosphorylation is under Cdk1 control. However, Cdk1 is inefficient at phosphorylating purified Borealin in vitro. A yeast orthologue of Borealin, Npl1, is dephosphorylated by the phosphatase Cdc14. We find no difference in the mobility shift of Borealin in human cells lacking either Cdc14A or Cdc14B. In contrast, the phosphatase inhibitor okadaic acid does delay the dephosphorylation of Borealin as cells exit mitosis. The proteasome inhibitor MG132 reduces Borealin phosphorylation in mitosis and increases the steady-state level of Borealin, especially in mutants lacking the C-terminus. However, a second, structurally unrelated proteasome inhibitor, lactacystin did not up-regulate Borealin. These results suggest that the effect of MG132 on Borealin is due to the inhibition of an intracellular protease other than the proteasome.