Expression of Simian Virus 40 T antigens in Intestine

描述(申请人提供)：我们一直在使用猴病毒40(SV40)编码的708大T抗原来探索细胞增殖和死亡的机制。T抗原足以在培养中诱导多种细胞类型的转化。然而，在转基因小鼠系统中，T抗原表达的影响取决于细胞类型，反应范围从诱导增殖或癌症到细胞死亡。此外，T抗原具有多种转化功能，转化所需的功能(S)也取决于细胞类型。我们一直在研究小鼠的肠道，以探索细胞生长控制的调节。肠道由隐窝和绒毛组成，隐窝含有干细胞和增殖细胞群，绒毛由生长受阻的终末分化细胞组成。大T抗原在肠上皮细胞中的表达诱导它们重新进入细胞周期，导致肠上皮细胞增生，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)可使Rb失活，但缺少P53相互作用区域，也可诱导增殖。我们的结论是，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殖状态，但表达野生型T抗原的小鼠的肠道随着年龄的增长而进展为异型增生。因此，异型增生需要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殖或异型增生中都不起作用。在这一应用中，我们试图：(1)了解T抗原诱导的增殖机制；(2)确定T抗原靶点和细胞通路(S)，以发展到异型增生所需的。

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.