STRUCTURE AND FUNCTION OF THE SV40 SMALL T ANTIGEN

SV 40小T抗原增强病毒大T-T抗原转化 并且这需要至少两个小T域的功能。 的 首先福尔斯落在氨基酸97-103内，并影响小T的能力， 抑制蛋白磷酸酶2A。 PP 2A抑制与 小T细胞激活多种细胞激酶（MAPK，MEK， JNK 1）和刺激AP 1 DNA结合活性。 增加的AP 1 活性导致含有细胞周期蛋白D1的构建体的反式激活 小T启动子 拟议的实验将确定机制 增加AP 1活性和小t在调节细胞周期蛋白D1中的作用 在自然感染中的表达（目的1）。 第二个领域，42-47 区域域，也需要在小t依赖的转换 系统. 初步结果表明，这一领域是必要的， 小T反式激活细胞周期蛋白。 瞬时启动子 测定和增强内源性细胞周期蛋白A基因的表达。 42- 将对47个区域进行遗传学研究，以确定转化是否 和反式激活功能可以分离，以及小t和 大T抗原在提供42-47区功能方面同样起作用 (aim 2）。 拟议的实验将探索细胞周期蛋白A中的序列 启动子，小T转录所需的，并定义片段 启动子的启动子，足以小T反应时，放置 转化为最小的报告基因构建体（aim 3）。 部分基于 细胞周期蛋白A启动子的研究，几种可能的机制， 将测试small-t可能采取行动（目标4）。 小t的潜在影响 细胞周期蛋白A是更大的兴趣，鉴于最近的报告，根据 限制性生长条件如缺乏锚定，细胞可 由于细胞周期蛋白A表达受阻而无法生长。 因此，最终目标 探讨小t抗原对细胞周期蛋白A表达的影响。 因此，最终的目标是探索小T抗原对细胞周期蛋白的影响。 在细胞周期蛋白A的表达受到限制的细胞中A水平。 结果 这些研究可以解释为什么对小T抗原的需求 在生长停滞的细胞中以及在 需要转化细胞的非贴壁依赖性生长。

The SV40 small-t antigen enhances transformation by viral large-T-T antigen and this requires the functions of at least two domains of small-t. The first falls within amino acids 97-103 and affects the ability of small-t to inhibit protein phosphatase 2A. PP2A inhibition correlates with the ability of small-t to activate a variety of cellular kinases (MAPK, MEK, JNK1) and to stimulate AP1 DNA binding activity. The increased AP1 activity results in transactivation of constructs that contain a cyclin D1 promoter by small-t. Proposed experiments will determine the mechanisms for increased AP1 activity and the role of small-t in regulating cyclin D1 expression in natural infections (aim 1). The second domain, the 42-47 region domain, is also required for transformation in small-t dependent systems. Preliminary results have shown that this domain is required for small-t to transactivate the cellular cyclin. A promoter in transient assays and to enhance expression of the endogenous cyclin A gene. The 42- 47 region will be probed genetically to determine whether transformation and transactivation functions can be separated and whether small-t and large-T antigens contribute equally in providing the 42-47 region function (aim 2). Proposed experiments will explore sequences in the cyclin A promoter that are required for small-t transactivation, and define segments of the promoter that are sufficient for small-t responsiveness when placed into minimal reporter constructs (aim 3). Based in part on results of studies of the cyclin A promoter, several possible mechanisms through which small-t may act will be tested (aim 4). The potential effect of small-t on cyclin A is of even greater interest given recent reports that, under restrictive growth conditions such as the absence of anchorage, cells may fail to grow because of a block to cyclin A expression. Thus, a final goal is to explore the effects of small -t antigen on cyclin A expression. Thus, a final goal is to explore the effects of small-t antigen on cyclin A levels in cells in which cyclin A expression is restricted. Results of these studies may explain why a requirement for small-t antigen has most frequently been observed in growth-arrested cells and in assays that require the anchorage-independent growth of transformed cells.