Department of Radiation Oncology, Houston Methodist Hospital Research Institute, Houston, TX 77030, USA, Department of Oncology, Drug Discovery Division, Southern Research Institute, Birmingham, AL 35205, USA.
Department of Radiation Oncology, Houston Methodist Hospital Research Institute, Houston, TX 77030, USA, Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin 300052, China.
Carcinogenesis. 2014 Sep;35(9):2007-13. doi: 10.1093/carcin/bgu087. Epub 2014 Apr 11.
The spindle assembly checkpoint (SAC), which blocks anaphase onset until all chromosomes have bi-oriented, is one of the key self-monitoring systems of the eukaryotic cell cycle for genome stability. The mitotic arrest-deficient protein 1 (Mad1), a critical component of the SAC, is hyperphosphorylated in mitosis. However, the kinases responsible for Mad1 phosphorylation and its functional significance are not fully understood. Here we report that Mad1 is phosphorylated on Serine 214 by the Ataxia-Telangiectasia Mutated (ATM) kinase, a critical DNA damage response protein also activated in mitosis and required for the SAC. We demonstrate that Mad1 Serine 214 phosphorylation promotes the formation of homodimerization of Mad1 and its heterodimerization with Mad2. Further we show that Mad1 Serine 214 phosphorylation contribute to activation of the SAC and the maintenance of chromosomal stability. Together, these findings reveal an important role of ATM-mediated Mad1 Serine 214 phosphorylation in mitosis.
纺锤体组装检查点（SAC）是真核细胞周期中基因组稳定性的关键自我监测系统之一，它阻止后期起始，直到所有染色体都双定向。有丝分裂阻滞缺陷蛋白 1（Mad1）是 SAC 的关键组成部分，在有丝分裂中被高度磷酸化。然而，负责 Mad1 磷酸化及其功能意义的激酶尚未完全阐明。在这里，我们报告 Mad1 被共济失调毛细血管扩张突变蛋白（ATM）激酶磷酸化，该激酶磷酸化丝氨酸 214，是一种关键的 DNA 损伤反应蛋白，也在有丝分裂中被激活，并且是 SAC 所必需的。我们证明 Mad1 丝氨酸 214 磷酸化促进 Mad1 同源二聚体的形成及其与 Mad2 的异源二聚体的形成。此外，我们表明 Mad1 丝氨酸 214 磷酸化有助于 SAC 的激活和染色体稳定性的维持。总之，这些发现揭示了 ATM 介导的 Mad1 丝氨酸 214 磷酸化在有丝分裂中的重要作用。
