Transformation of Epithelial Cell by E6 Oncogene

描述(申请人提供)：宫颈癌与人类乳头瘤病毒(HPV)的几个特定亚型有关。然而，这些高危HPV转化细胞的分子机制尚不完全清楚。HPV的两个转化癌蛋白E6和E7是启动和维持细胞转化所必需的。E6的转化功能部分是通过诱导泛素化和降解P53抑癌蛋白来实现的。然而，E6也具有不依赖于p53的转化活动，人们对此了解甚少。这些额外的E6活性在HPV引起的癌症的发病机制中起着关键作用。最近，我们克隆并鉴定了一种新的人类E6结合蛋白MAML1，它选择性地与来自高危HPV16型的E6相互作用。MAML1与果蝇黑腹主脑基因相关，该基因是Notch信号通路的一个组成部分，参与细胞命运的决定。我们发现，MAML1是一种核蛋白，可以作为哺乳动物Notch受体的转录辅助激活因子。这些研究现在导致我们克隆和鉴定了这个新的哺乳动物策划者家族的另外两个成员，MAML2和MAML3。和MAML1一样，MAML2和MAML3都优先结合高危HPV16的E6。此外，高危HPV16E6蛋白可阻断Notch信号转导。因此，MAML家族提供了乳头瘤病毒癌蛋白和Notch途径之间的第一个直接联系。这项建议的目的是确定HPV E6与三个哺乳动物主脑家族成员在E6介导的细胞转化中相互作用的机制和意义。有待检验的假设是，HPVE6通过MAML家族与Notch途径相互作用，在细胞转化中发挥关键作用。具体地说，我们假设E6-MAML的相互作用导致Notch信号的改变，并导致宫颈上皮细胞的生长和分化失控。作为选择或组合，E6-MAML相互作用可能是E6转化活动所必需的，涉及细胞增殖、细胞周期调节和衰老。为了验证这些假说，我们将1)确定高危E6蛋白与MAML蛋白的相互作用是否在E6介导的细胞转化中起关键作用；2)确定E6和MAML蛋白的相互作用是否以及如何通过Notch信号促进细胞转化。这项研究将促进我们对宫颈癌转化的分子机制的理解，并为深入了解新的MAML家族和Notch信号通路提供帮助。

DESCRIPTION (provided by applicant): Cervical carcinomas are associated with a few specific subtypes of the human papillomavirus (HPV). However, the molecular mechanisms of cellular transformation by these "high-risk" HPV are not fully understood. Two transforming oncoproteins of HPV, E6 and E7, are required for both initiation and maintenance of cellular transformation. The transforming function of E6 is mediated partially by its ability to induce ubiquitination and degradation of the p53 tumor suppressor protein. However, E6 also has poorly understood transformation activities that are p53-independent. These additional E6 activities have critical roles in the pathogenesis of cancers caused by HPV. Recently, we cloned and characterized a novel human E6-binding protein, MAML1 (mastermind-like-I) that selectively interacts with E6 from high-risk HPV type 16. MAML1 is related to the Drosophila melanogaster mastermind gene, a component of the Notch signaling pathway involved in cell fate determination. We found that MAML1, a nuclear protein, functions as a transcriptional co-activator for mammalian Notch receptors. These studies have now led to our cloning and characterization of two additional members of this novel mammalian mastermind family, MAML2 and MAML3. Like MAML1, both MAML2 and MAML3 preferentially bind to E6 from high-risk HPV16. Furthermore, high-risk HPV16 E6 proteins block Notch signaling. Therefore, the MAML family provides the first direct link between papillomavirus oncoproteins and the Notch pathway. The, goal of this proposal is to determine the mechanisms and significance of the HPV E6 interactions with the three mammalian mastermind family members in E6-mediated cellular transformation. The hypothesis to be tested is that HPV E6 interactions with the Notch pathway, via the MAML family, have a critical role in cellular transformation. Specifically, we hypothesize that E6-MAML interactions result in altered Notch signaling and lead to deregulated growth and differentiation in cervical epithelial cells. Alternatively or in combination, E6-MAML interactions may be required for E6 transformation activities involving cell proliferation, cell cycle regulation and senescence. To test these hypotheses, we will 1) determine whether the interactions of high-risk E6 proteins with MAML proteins are critical for E6 mediated cellular transformation, 2) determine whether and how the interactions of E6 and MAML proteins contribute to cellular transformation via Notch signaling. The proposed research will advance our understanding of the molecular mechanisms of transformation of cervical cancers, as well as provide insight into the novel MAML family and the Notch signaling pathway.