Nguyen Hao G, Chinnappan Dharmaraj, Urano Takeshi, Ravid Katya
Department of Biochemistry, Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, K225, Boston, MA 02118, USA.
Mol Cell Biol. 2005 Jun;25(12):4977-92. doi: 10.1128/MCB.25.12.4977-4992.2005.
The kinase Aurora-B, a regulator of chromosome segregation and cytokinesis, is highly expressed in a variety of tumors. During the cell cycle, the level of this protein is tightly controlled, and its deregulated abundance is suspected to contribute to aneuploidy. Here, we provide evidence that Aurora-B is a short-lived protein degraded by the proteasome via the anaphase-promoting cyclosome complex (APC/c) pathway. Aurora-B interacts with the APC/c through the Cdc27 subunit, Aurora-B is ubiquitinated, and its level is increased upon treatment with inhibitors of the proteasome. Aurora-B binds in vivo to the degradation-targeting proteins Cdh1 and Cdc20, the overexpression of which accelerates Aurora-B degradation. Using deletions or point mutations of the five putative degradation signals in Aurora-B, we show that degradation of this protein does not depend on its D-boxes (RXXL), but it does require intact KEN boxes and A-boxes (QRVL) located within the first 65 amino acids. Cells transfected with wild-type or A-box-mutated or KEN box-mutated Aurora-B fused to green fluorescent protein display the protein localized to the chromosomes and then to the midzone during mitosis, but the mutated forms are detected at greater intensities. Hence, we identified the degradation pathway for Aurora-B as well as critical regions for its clearance. Intriguingly, overexpression of a stable form of Aurora-B alone induces aneuploidy and anchorage-independent growth.
激酶Aurora - B是染色体分离和胞质分裂的调节因子，在多种肿瘤中高表达。在细胞周期中，这种蛋白质的水平受到严格控制，其丰度失调被怀疑与非整倍体的形成有关。在此，我们提供证据表明Aurora - B是一种通过后期促进复合体（APC/c）途径被蛋白酶体降解的短命蛋白。Aurora - B通过Cdc27亚基与APC/c相互作用，Aurora - B被泛素化，并且在用蛋白酶体抑制剂处理后其水平会升高。Aurora - B在体内与靶向降解蛋白Cdh1和Cdc20结合，它们的过表达会加速Aurora - B的降解。通过对Aurora - B中五个假定降解信号进行缺失或点突变，我们发现该蛋白的降解不依赖于其D盒（RXXL），但确实需要位于前65个氨基酸内完整的KEN盒和A盒（QRVL）。用与绿色荧光蛋白融合的野生型、A盒突变型或KEN盒突变型Aurora - B转染的细胞在有丝分裂期间显示该蛋白定位于染色体，然后定位于中间区，但突变形式的强度更高。因此，我们确定了Aurora - B的降解途径及其清除的关键区域。有趣的是，单独过表达稳定形式的Aurora - B会诱导非整倍体和不依赖贴壁生长。
