Tumor Host Range Mutants of Polyoma and Their Targets

描述（由申请人提供）：我们建议继续分离和表征多瘤病毒的“肿瘤宿主范围”（THR）突变体，以努力识别和表征病毒T（肿瘤）抗原的细胞靶点。这种选择背后的基本原理是，肿瘤细胞可能已经丧失了野生型病毒通常针对的特定功能。这些功能可能代表肿瘤抑制基因或其他复制和存活的调节因子，病毒需要以某种方式使其失活或改变，以便有效地复制。选择THR突变体是为了能够在某些肿瘤细胞上生长，但不能在正常细胞上生长，并且被认为已经失去了靶向功能。一个THR突变体被用来鉴定多锌指同源转录因子Sal2作为多瘤大T抗原的靶标。我们已经证明，Sal2在一些重要方面发挥作用，如p53，就其生长抑制和诱导细胞凋亡的特性而言。在本应用中，我们将重点关注Sal2，努力确定其下游细胞基因靶点，上游调节因子和蛋白质伙伴。表达谱分析和染色质免疫沉淀（ChIP）将用于这些研究。我们还将根据它们的相互作用来确定大T和Sal2相互作用的相互影响。Sal2在卵巢表面上皮细胞中高度表达。初步证据表明，Sal2在人卵巢癌中表达缺失。我们建议进一步研究这种损失是否发生以及在各种形式的卵巢癌中发生的频率。我们将验证这一假设，即在某些卵巢癌病例中，两个可选的Sal2启动子之一的启动子甲基化可能导致Sal2沉默。最后，我们将采用几种方法来开发卵巢癌小鼠模型，基于最近发现的大的T-Sal2相互作用，以及在某些小鼠品系中有效诱导卵巢表面上皮肿瘤的一种新的多瘤菌株的分离。

DESCRIPTION (provided by applicant): We propose to continue to isolate and characterize "tumor host range" (THR) mutants of polyoma virus in efforts to identify and characterize the cellular targets of the viral T (tumor) antigens. The rationale behind this selection is that tumor cells may have undergone the loss of particular function(s) which the wild type virus normally targets. These functions may represent tumor suppressor genes or other regulators of replication and survival which the virus needs to inactivate or alter in some manner in order to replicate efficiently. THR mutants are selected to be able to grow on certain tumor cells but not on normal cells and are presumed to have lost the targeting function. One THR mutants has been used to identify the multi-zinc finger homeotic transcription factor Sal2 as a target of the polyoma large T antigen. We have shown that Sal2 acts in some important respects like p53 in terms of its growth arrest and apoptosis inducing properties. In this application we focus on Sal2 with efforts to determine its downstream cellular gene targets, upstream regulators and protein partners. Expression profiling analysis and chromatin immunoprecipitation (ChIP) will be used in these investigations. We will also seek to determine the mutual effects which large T and Sal2 exert on each other based on their interaction. Sal2 is highly expressed in ovarian surface epithelial cells. Preliminary evidence indicates that Sal2 expression is lost in human ovarian carcinomas. We propose to examine further if such loss occurs and at what frequency in various forms of ovarian carcinoma. We will test the hypothesis that promoter methylation in one of the two alternative Sal2 promoters may account for Sal2 silencing in some cases of ovarian carcinoma. Finally, we will take several approaches to developing a mouse model of ovarian cancer based on recent findings on the large T-Sal2 interaction and on the isolation of a new strain of polyoma which efficiently induces ovarian surface epithelial tumors in certain strains of mice.