Products of the Transforming Genes of Polyomavirus

小鼠多瘤病毒为肿瘤转化提供了一个有价值的模型。该病毒在动物中引起广泛的肿瘤。这意味着在实验室开发的引线可以很容易地在宿主体内进行测试。对多瘤的研究一再提供了对细胞生长调节的基本机制的见解。酪氨酸激酶信号传导和磷脂酰肌醇3-激酶（PI3K）信号传导是多瘤研究揭示的两个基本机制。中T抗原（MT）是多瘤病毒的主要转化蛋白。对于多瘤细胞转化，它总是必要的，而且常常是充分的。这个子项目将在上一个项目期间开发的线索的基础上扩展我们对MT及其信号的知识。有4个具体目标。1)我们已经证明MT激活了小的GTPase Ral。我们将研究MT如何激活Ral。我们将测试Ral在MT转型中的作用。由于Ral在包括分泌在内的贩运过程中起作用，我们将在那里测试MT的功能。2) MT诱导骨桥蛋白，一种被认为与转化和转移有关的分泌蛋白。我们将确定MT如何调节骨桥蛋白。我们将确定骨桥蛋白的作用

Murine polyomavirus provides a valuable model for neoplastic transformation. The virus causes a broad spectrum of tumors in animals. This means that leads developed in the laboratory can be readily tested in the host. Studies on polyoma have repeatedly provided insight into basic mechanisms of cellular growth regulation. Tyrosine kinase signaling and phosphatidylinositol 3-kinase (PI3K) signaling are two fundamental mechanisms uncovered from studies on polyoma. Middle T antigen (MT) is the major transforming protein of polyomavirus. It is always necessary, and often sufficient, for cellular transformation by polyoma. This subproject will extend our knowledge of MT and its signaling based on leads developed in the previous project period. There are 4 specific aims. 1) We have shown that MT activates the small GTPase Ral. We will examine how MT activates Ral. We will test the role of Ral in MT transformation. Since Ral functions in trafficking processes including secretion, we will test MT function there. 2) MT induces osteopontin, a secreted protein thought to be linked to transformation and metastasis. We will determine how MT regulates osteopontin. We will determine the role of osteopontin in MT transformation by examining tumor profiles. Using breast cancer and hemangioma models, we will test the role of osteopontin in metastasis and in cell recruitment. We will initiate structural analysis of MT using NMR to determine the structure of the portion of MT that interacts with downstream targets such as Shc and PI3K. We will then map the interaction surface between MT and p85 of PI3K or Shc. Finally, there is strong genetic evidence suggesting that there are undiscovered MT binding proteins. We will use tandem affinity purification and mass spectrometry to identify them. We will determine the MT sequences required for their interaction. We will test their function in MT assays for transformation.