Hh信号通路作为最为保守的信号途径之一，控制着发育过程中细胞的增殖与分化。Hh信号通路的异常将会导致包括出生缺陷及癌症、肥胖在内的多种发育异常和恶性疾病。Smo蛋白作为Hh通路的信号转换元件，是激活Hh信号通路的充分必要因子。Smo蛋白质转录后水平的调控是Hh通路传导调节机制中最重要的环节之一。最新的报道发现了Smo蛋白可以被泛素化修饰，但是泛素化对Smo活性调控的分子机制还不明朗。更重要的是，能够功能性的调控Smo泛素化水平的泛素连接酶和去泛素酶仍然未知。在模式生物果蝇中，通过靶向性的体内RNAi筛选，我们发现了可能调控Smo的泛素化水平的泛素连接酶和去泛素酶基因。我们将深入探索这两个新基因对Smo活性及Hh信号传导的调控机制。研究表明磷酸化修饰和细胞膜定位都是激活Smo所必需的，但是它们与泛素化之间是否存在调控关系完全未知，本申请将着重对此进行研究, 以阐释对Smo活性调控的整合机制。

As one of the most conserved signal transduction pathways, Hh signaling regulates cell proliferation and differentiation during many development processes. Dis-regulation of Hh signaling always leads to birth defects and malignant diseases such as cancer and obesity. Smo protein functions as the signal sensor during Hh signal transduction and is both necessary and sufficient for Hh signal activation. Post-translation modifications on Smo protein play important roles in regulating the Hh signaling. Recently, it has been reported that Smo can be ubiquitinated, but the underlying molecular mechanism is still not clear. More importantly, the ubiquitin ligase and deubiquitinase that functionally regulates Smo ubiquitination are unknown. Utilizing a targeted in vivo RNAi screen in Drosophila, we have identified genes that encode ubiquitin ligase and deubiquitinase that may recognize Smo as their substrate. In this proposal, we will investigate how these two novel genes regulate Smo ubiquitination and Hh signaling activity. Detailed analysis of their genetic and biochemical functions will provide important insights on new regulatory mechanism of Hh signal transduction. It has been shown that Smo protein phosphorylation and membrane relocalization are required for its activation, but whether and how do they work together with Smo ubiquitination is entirely unknown. We will focus on dissecting the relationship among these three events and gain a more integrative view on Smo activity regulation.