Expression of Simian Virus 40 T antigens in Intestine

描述（由申请人提供）：我们一直在使用猿猴病毒40 （SV40）编码的708大T抗原来探索细胞增殖和死亡的机制。T抗原在培养中足以诱导多种细胞类型的转化。然而，在转基因小鼠系统中，T抗原表达的影响是细胞类型依赖的，其反应范围从诱导增生或癌到细胞死亡。此外，T抗原具有多种转化功能，转化所需的功能也取决于细胞类型。我们一直在研究小鼠肠道，以探索细胞生长控制的调控。肠由隐窝和绒毛组成，隐窝含有干细胞和增殖细胞群，绒毛由生长受阻、终末分化的细胞组成。肠细胞中大T抗原的表达诱导它们重新进入细胞周期，导致肠道增生，这依赖于T抗原与肿瘤抑制因子rb家族的相互作用。此外，T抗原的氨基末端片段（dl1137）使Rb失活，但缺少p53相互作用结构域，也会诱导增生。我们得出结论，诱导肠细胞增殖需要T抗原与rb家族的一个或多个成员相互作用。有趣的是，虽然表达dl1137的小鼠的肠道仍处于增生状态，但那些表达野生型T抗原的小鼠随着年龄的增长而发展为发育不良。因此，发育不良需要T抗原的羧基末端。我们已经证明T抗原与p53的相互作用在诱导增生或不典型增生中都不起作用。在这个应用中，我们寻求：(1)了解T抗原诱导增生的机制；(2)确定T抗原靶点和发育不良所需的细胞途径。

DESCRIPTION (provided by applicant): We have been using the 708 large T antigen encoded by simian virus 40 (SV40) to probe mechanisms of cell proliferation and death. T antigen is sufficient to induce transformation in a number of cell-types in culture. However, in transgenic mouse systems the effect of T antigen expression is cell-type dependent with responses ranging from induction of hyperplasia or carcinoma to cell death. Furthermore, T antigen possesses multiple transforming functions and which function(s) is(are) required for transformation also depends on the cell-type. We have been studying the mouse intestine to explore the regulation of cellular growth control. The intestine consists of the crypts, which contain stem cells and a proliferating cell population, and the villi, which are composed of growth-arrested, terminally differentiated cells. Expression of large T antigen in enterocytes induces their reentry into the cell cycle resulting in an intestinal hyperplasia that is dependent upon the interaction of T antigen with the Rb-family of tumor suppressors. Furthermore, an amino-terminal fragment of T antigen (dl1137) that inactivates Rb but is missing the p53 interaction domain, also induces hyperplasia. We conclude that the induction of enterocyte proliferation requires an interaction of T antigen with one or more members of the Rb-family. Interestingly, while the intestines of mice expressing dl1137 remain at hyperplasia, those expressing wild-type T antigen progress with age to dysplasia. Thus, dysplasia requires carboxy-terminal of T antigen. We have shown that T antigen interaction with p53 does not play a role in either induction of hyperplasia or dysplasia. In this application, we seek to: (1) understand the mechanism of T antigen-induced hyperplasia; and, (2) identify the T antigen target and cellular pathway(s) required for progression to dysplasia.