【作者】 高霞；

【导师】 陈晔光；

【作者基本信息】 清华大学 ， 生物学， 2009， 博士

【摘要】 由β-catenin和LEF/TCF家族转录因子激活的经典Wnt信号通路,通过调控细胞增殖、分化以及存活过程中所涉及的重要基因的表达在胚胎发育和癌症发生过程中起着重要的作用。Dapper1(Dpr1),作为Dishevelled的相互作用因子,被认为可以通过促进Dishevelled降解来调控Wnt信号。本研究中我们证明了Dpr1穿梭于细胞质和细胞核之间。尽管过量表达的Dpr1被发现主要存在于细胞质中,内源的Dpr1定位于整个细胞并且Wnt1刺激能够促进它的细胞质聚集。Exportin抑制剂Leptomycin B处理能够引起内源以及过量表达Dpr1聚集于细胞核中,表明Dpr1穿梭于细胞质和细胞核之间。我们进而发现了Dpr1的入核信号NLS以及出核信号NES。利用报告基因实验以及体内斑马鱼胚胎实验,我们证明了细胞核定位的Dpr1突变体依然保持抑制Wnt信号的能力。进而我们发现Dpr1分别和β-catenin以及LEF1相互作用并破坏它们之间复合物的形成。此外,Dpr1可以和HDAC1结合并增强LEF1-HDAC1相互作用。总之,我们的发现提示Dpr1在细胞核内通过保持LEF1处于转录抑制状态来负调控Wnt/β-catenin信号的基础活性。因而,Dpr1既能在细胞质又能在细胞核内调控Wnt/β-catenin信号。更多还原

【Abstract】 Wnt signaling, via the activation of the canonicalβ-catenin and lymphoid enhancer factor/T-cell factor (LEF/TCF) pathway, plays an important role in embryogenesis and cancer development by regulating the expression of genes involved in cell proliferation, differentiation and survival. Dapper1 (Dpr1), as a Dishevelled interactor, has been suggested to modulate Wnt signaling by promoting Dishevelled degradation. Here, we provide evidence that Dpr1 shuttles between the cytoplasm and the nucleus. Although overexpressed Dpr1 was mainly found in the cytoplasm, endogenous Dpr1 were localized over the cell and Wnt1 induced its nuclear export. Treatment with leptomycin B induced nuclear accumulation of both endogenous and overexpressed Dpr1, suggesting that Dpr1 shuttles between the cytoplasma and the nucleus. We further identified the nuclear localization signal and the nuclear export signal within Dpr1. Using reporter assay and in vivo zebrafish embryo assay, we demonstrated that the forced nuclear localization of Dpr1 possessed the ability to antagonize Wnt signaling. Dpr1 interacted withβ-catenin and LEF1 and disrupted their complex formation. Furthermore, Dpr1 could associate with HDAC1 and enhance the LEF1-HDAC1 interaction. Together, our findings suggest that Dpr1 negatively modulates the basal activity of Wnt/β-catenin signaling in the nucleus by keeping LEF1 in the repressive state. Thus, Dpr1 controls Wnt/β-catenin signaling in both the cytoplasm and the nucleus.更多还原