School of Life Sciences, Tsinghua University, Beijing 100084, China.
Biochem Biophys Res Commun. 2011 Jan 7;404(1):413-8. doi: 10.1016/j.bbrc.2010.11.135. Epub 2010 Dec 3.
NuSAP is a microtubule-associated protein that plays an important role in spindle assembly. NuSAP deficiency in mice leads to early embryonic lethality. Spindle assembly in NuSAP-deficient cells is highly inefficient and chromosomes remain dispersed in the mitotic cytoplasm. ATM is a key kinase that phosphorylates a series of substrates to mediate G1/S control. However, the role of ATM at the G2/M phase is not well understood. Here we demonstrate that ectopic expression of NuSAP lead to mitotic arrest observably dependent on the kinase activity of ATM. When endogenous ATM was depleted or its kinase activity was inhibited, NuSAP could not cause mitotic arrest. We further show ATM interacts with NuSAP and phosphorylates NuSAP on Ser124. The phosphorylation and interaction occur specifically at G2/M-phase. Collectively, our work has uncovered an ATM-dependent checkpoint pathway that prevents mitotic progression by targeting a microtubule-associated protein, NuSAP.
NuSAP 是一种微管相关蛋白，在纺锤体组装中发挥重要作用。NuSAP 缺失的小鼠会导致早期胚胎致死。NuSAP 缺失的细胞中的纺锤体组装效率非常低，染色体仍然分散在有丝分裂细胞质中。ATM 是一种关键的激酶，可磷酸化一系列底物来介导 G1/S 控制。然而，ATM 在 G2/M 期的作用尚不清楚。在这里，我们证明了 NuSAP 的异位表达导致有丝分裂停滞，明显依赖于 ATM 的激酶活性。当内源性 ATM 被耗尽或其激酶活性被抑制时，NuSAP 不能引起有丝分裂停滞。我们进一步表明，ATM 与 NuSAP 相互作用，并在丝氨酸 124 上磷酸化 NuSAP。这种磷酸化和相互作用仅发生在 G2/M 期。总之，我们的工作揭示了一种 ATM 依赖性的检查点途径，通过靶向微管相关蛋白 NuSAP 来阻止有丝分裂的进行。
