Department of Biological Sciences and Institute of Molecular Biology and Genetics, Seoul National University, South Korea.
FEBS J. 2017 Dec;284(23):4035-4050. doi: 10.1111/febs.14286. Epub 2017 Nov 1.
BubR1 acetylation is essential in spindle assembly checkpoint (SAC) signaling. Here we show that BubR1 deacetylation is a signal that initiates mitotic exit. Sustained BubR1 acetylation arrests the cells in metaphase, although chromosome congression is achieved. BubR1 deacetylation was coordinated with dephosphorylation in mitotic exit, suggesting the presence of a coordinated acetylation-phosphorylation code in mitotic signaling. Histone deacetylase (HDAC) 2 and 3 bound to acetylated BubR1 exclusively in mitosis and led to the polyubiquitination of BubR1. Subsequent degradation of BubR1 resulted in the disassembly of the mitotic checkpoint complex. Importantly, BRCA2 was required for HDAC2/3 association with acetylated BubR1 in nocodazole (Noc)-arrested cells. Plk1, PP2A, P300/CBP-associated factor (PCAF) and BubR1 were found in the mitotic BRCA2 complex, suggesting that BRCA2 acts as a signaling scaffold for BubR1 modification. Furthermore, we show that Plk1 is required for BRCA2 to localize at the prometaphase kinetochore (KT). Inhibition of Plk1 resulted in the loss of BRCA2 from the KT, and so did PCAF, consistent with the loss of BubR1 acetylation. Concordantly, BRCA2-dysfunctional cells exhibited resistance to trichostatin A, which was restored when BRCA2 was introduced. That loss of Brca2 conferred resistance to various HDAC inhibitors was corroborated by the experiments in mouse pancreatic organoids. These results suggest that the BRCA2-BubR1 acetylation-deacetylation pathway is an important decision-making point for the HDAC inhibitor response. Taken together, BRCA2 is a signaling platform for BubR1, and BubR1 deacetylation is a cue for SAC silencing.
BubR1 的乙酰化对于纺锤体组装检查点（SAC）信号至关重要。在这里，我们表明 BubR1 的去乙酰化是启动有丝分裂退出的信号。尽管染色体的趋同已经实现，但持续的 BubR1 乙酰化会使细胞停滞在中期。BubR1 的去乙酰化与有丝分裂退出时的去磷酸化相协调，这表明有丝分裂信号中存在协调的乙酰化-磷酸化密码。组蛋白去乙酰化酶（HDAC）2 和 3 仅在有丝分裂中与乙酰化的 BubR1 结合，并导致 BubR1 的多泛素化。随后 BubR1 的降解导致有丝分裂检查点复合物的解体。重要的是，在长春花碱（Noc）阻滞的细胞中，BRCA2 对于 HDAC2/3 与乙酰化 BubR1 的结合是必需的。Plk1、PP2A、P300/CBP 相关因子（PCAF）和 BubR1 都存在于有丝分裂的 BRCA2 复合物中，这表明 BRCA2 作为 BubR1 修饰的信号支架发挥作用。此外，我们还表明 Plk1 对于 BRCA2 在前期动粒（KT）的定位是必需的。Plk1 的抑制导致 BRCA2 从 KT 丢失，PCAF 也是如此，这与 BubR1 乙酰化的丢失一致。相应地，BRCA2 功能失调的细胞对 Trichostatin A 表现出耐药性，而当引入 BRCA2 时，这种耐药性得到恢复。Brca2 的丢失赋予了对各种 HDAC 抑制剂的耐药性，这在小鼠胰腺类器官的实验中得到了证实。这些结果表明，BRCA2-BubR1 乙酰化-去乙酰化途径是 HDAC 抑制剂反应的一个重要决策点。总之，BRCA2 是 BubR1 的信号平台，BubR1 的去乙酰化是 SAC 沉默的提示。
