Spindle Assembly Checkpoint, Chromosomal Instability, and Cancer

描述(申请人提供)：非整倍体是绝大多数人类实体肿瘤的特征。有丝分裂检查点基因的突变，如Bub1、BUBR1或MAD2，已被证明与非整倍体的产生有关。这些检查点基因产物形成了一个复杂的信号网络，称为纺锤体组装检查点(SAC)，它推迟姐妹染色单体的分离，直到所有的染色体都正确地连接到有丝分裂的纺锤体上并在中期平板上排列。酵母等低等生物的研究已经清楚地表明，检查点功能的丧失会导致染色体的不稳定，表现为染色体的增减。从酵母和高等真核生物的分析中，SAC的更详细的分子图像正在浮现。然而，SAC及其在生物体水平上的各种成分的功能仍有待阐明。同样，缺乏对哺乳动物SAC的机械解剖。为了开始对哺乳动物SAC进行分子解剖，并确定其在防止染色体不稳定和致癌转化中的功能，我们产生了不同程度SAC缺陷的小鼠品系。这些菌株是Securin缺失、非磷酸化分离酶敲打蛋白和MAD2-非抑制的CDC20敲打蛋白(AAA-CDC20)。我们发现我们的AAA-CDC20小鼠容易患肿瘤。我们建议在SAC突变体中探讨AAA-CDC20促进肿瘤发生的机制以及P53在限制肿瘤发展中的作用。公共卫生相关性：本项目重点研究纺锤体装配检查点在预防基因组不稳定和肿瘤发生中的作用。从拟议的实验中获得的结果可能有助于癌症的治疗和诊断。

DESCRIPTION (provided by applicant): Aneuploidy is a hallmark of the vast majority of human solid tumors. Mutations in mitotic checkpoint genes such as BUB1, BUBR1 or MAD2 have been shown to be involved in generation of aneuploidy. These checkpoint gene products forms an intricate signaling network called spindle assembly checkpoint (SAC) that delays the segregation of sister chromatids until all chromosomes are properly attached to the mitotic spindle apparatus and aligned at the metaphase plate. Work from lower organisms such as yeast has clearly demonstrated that loss of the checkpoint function causes chromosomal instability manifested as gains or losses of chromosomes. A more detailed molecular picture of SAC is emerging from analyses in both yeast and higher eukaryotes. However, the function of SAC and its various components at an organismal level remains to be elucidated. Likewise, mechanistic dissection of SAC in mammals is lacking. In an effort to start to molecularly dissect SAC in mammals and to determine its function in preventing chromosomal instability and oncogenic transformation, we generated mouse strains that are defective in SAC to different extents. These strains are securin deletion, non-phosphorylable separase knockin, and Mad2-noninhibitable Cdc20 knockin (AAA-Cdc20). We have found that our AAA-Cdc20 mice were tumor-prone. We propose to address the mechanism by which AAA-Cdc20 promotes tumorigenesis and the role of p53 in limiting tumor development in SAC mutants. PUBLIC HEALTH RELEVANCE: This project focuses on spindle assembly checkpoint's role in the prevention of genome instability and tumorigenesis. Results obtained from the proposed experiments may help the treatment and diagnosis of cancer.