Mechanism of beta-Catenin and APC-Regulated Transcription at Wnt Target Genes

描述(申请人提供)：这个项目的目标是了解Wnt/？-catenin反式激活的机制以及腺瘤性息肉病结肠(APC)对其调节，APC是一种在大多数人类结肠癌中突变的肿瘤抑制因子。初步数据显示，转移性肿瘤抑制因子β-连环蛋白通过APC肿瘤抑制因子的募集，以及抑制偶联的辅活化子和辅阻遏子复合体的交换，直接抑制Wnt/连环蛋白依赖的基因，导致DNA结合的Lef-1释放连环蛋白。APC和β-catenin核复合体的新成分将通过稳健和灵敏的蛋白质组学分析鉴定，并通过基因组芯片-序列分析(AIM 1)评估招募到Wnt调节点(AIM 1)，APC介导的抑制和辅助调节因子交换的详细机制将在HT29-APC结肠癌细胞(AIM 2)中定义，β-catenin在这一过程中的作用将在前列腺癌和结肠癌细胞中以及在一个新的无细胞检测系统中进行研究，该系统旨在了解β-catenin从Lef-1释放。总而言之，这些数据将识别控制依赖Wnt的癌细胞生长的新蛋白质，并揭示细胞核中APC和α-catenin肿瘤抑制因子以前未知的角色。

DESCRIPTION (provided by applicant): The goal of this project is to understand the mechanism of Wnt/¿-catenin transactivation and its regulation by the adenomatous polyposis coli (APC), a tumor suppressor that is mutated in the majority of human colon cancers. Preliminary data show that the metastatic tumor suppressor ¿-catenin, plays a direct role in the repression of Wnt/¿-catenin-dependent genes through recruitment of the APC tumor suppressor, and repression-coupled exchange of coactivator and corepressor complexes, resulting in release of ¿-catenin from DNA-bound LEF-1. Novel components of APC and ¿-catenin nuclear complexes will be identified by robust and sensitive proteomics analyses and assessed for recruitment to Wnt regulatory loci by genomic ChIP-Seq analysis (Aim 1), the detailed mechanism of APC-mediated repression and coregulator exchange will be defined in HT29-APC colon cancer cells (Aim 2), and the role of ¿-catenin in this process will be studied in prostate and colon cancer cells, as well as in a novel cell-free assay system developed to understand ¿- catenin release from LEF-1. Together, these data will identify new proteins that control Wnt-dependent cancer cell growth and reveal previously unknown roles for the APC and alpha-catenin tumor suppressors in the nucleus.