INTERFERONS AND CELL GROWTH REGULATION

干扰素（IFN）是多功能细胞因子家族， 是人体抵抗感染和某些癌症的一部分。 IFN主要通过诱导效应蛋白的合成起作用。 尽管IFN用于治疗各种人类癌症， 包括毛细胞白血病、慢性粒细胞白血病和卡波西氏病 肉瘤，其作为抗增殖剂的机制是 不太了解。 以前，我们描述了一种52 kDa的核磷蛋白（p202）， IFN处理后细胞中的水平升高20倍。本构 转染细胞中p2 O2的表达抑制生长。P2 O2已经 发现与视网膜母细胞瘤肿瘤抑制蛋白（pRb）结合。这 这一发现表明p2 O2在调节细胞周期中的潜在作用。 这一观点得到了潮汐观测的进一步支持， 与转录因子E2 F（E2 F-1/DP-1）在体外和体内的作用， 在瞬时转染试验中抑制E2 F介导的转录。 因此，p2 O2可能通过以下途径介导IFN的生长抑制活性： 抑制E2 F活性。 该项目的主要目标是确定p2 O2如何介导 IFN的生长抑制活性。我们假设p2 O2 通过抑制E2 F活性抑制细胞生长。为了验证我们的假设， 我们提出了三个具体目标：（1）研究是否构成 p2 O2的过度表达将细胞阻滞在细胞的特定阶段 周期为此目的，我们已经产生了鼠AKR-2B细胞系， 其中p2 O2的表达可以通过去除来选择性诱导 四环素(2)研究p2 O2如何抑制E2 F活性。要执行此操作， 我们建议将p2 O2结合域定位在E2 F-1中，并测试是否 p_2O_2可抑制E_2F与DNA的结合。(3)为了检查增长- P202的调节活性。为此，我们计划将 p202中的生长抑制结构域。 这些研究将有助于我们对细胞的理解 IFN的生长抑制活性。

The interferons (IFNs) are a family of multifunctional cytokines that are part of the human body's defenses against infections and some cancers. IFNs act primarily by inducing the synthesis of effector proteins. Although IFNs are used in the treatment of various human cancers, including hairy cell leukemia, chronic myelogenous leukemia, and Kaposi's sarcoma, the mechanisms by which they act as antiproliferative agents are poorly understood. Previously, we characterized a 52-kDa nuclear phosphoprotein (p202) whose level rises 20-fold in cells following IFN treatment. Constitutive expression of p2O2 in transfected cells inhibits growth. p2O2 has been found to bind to the retinoblastoma tumor suppressor protein (pRb). This finding indicates a potential role for p2O2 in regulating the cell cycle. This notion is further supported by tide observations that p2O2 associated with the transcription factor E2F (E2F-1/DP-1) in vitro and in vivo and inhibited E2F-mediated transcription in transient transfection assays. Thus, p2O2 might mediate the growth-inhibitory activities of the IFNs by inhibiting E2F activity. The major goal of the proposed project is to determine how p2O2 mediates the growth-inhibitory activities of the IFNs. We hypothesize that p2O2 inhibits cell growth by inhibiting E2F activity. To test our hypothesis, we propose three specific aims: (1) To examine whether constitutive overexpression of p2O2 arrests cells in a particular phase of the cell cycle. For this purpose, we have generated murine AKR-2B cell lines in which the expression of p2O2 can be selectively induced by removal of tetracycline. (2) To determine how p2O2 inhibits E2F activity. To do this, we propose to localize the p2O2 binding domain in E2F-1 and test whether p2O2 would inhibit the DNA-binding of E2F. (3) To examine the growth- regulatory activities of p202. For this purpose, we plan to localize the growth-inhibitory domain in p202. The proposed studies will contribute to our understanding of the cell growth-inhibitory activities of the IFNs.