TRANSCRIPTION ACTIVATION BY HIV TAT, HTLV TAX AND HBV PX

动物病毒的复制依赖于许多成分 由细胞提供。 例如，病毒基因的转录 需要细胞通用转录因子以及某些 序列特异性 DNA 结合蛋白。 通常，动物病毒编码 通过细胞转录因子发挥作用的调节蛋白 优先表达病毒基因。 了解这些病毒如何 调节蛋白的功能对于理解病毒至关重要 复制并可能提示治疗干预的可能性。 我们 一直在研究转录调控的机制 三种病原病毒的蛋白质激活转录：Tat 人类免疫缺陷病毒 (HIV) 的蛋白质，Tax 蛋白质 f 人类 T- 细胞白血病病毒（HTLV）和乙型肝炎病毒（HBV）的pX蛋白。 HIV Tat 蛋白对于病毒复制至关重要，并以独特的方式发挥作用 时尚；它与新生的 HIV RNA 结合以增加转录 引发和伸长。 在过去的资助期间，我们定义了 Tat 响应所需的最少组件，并开发了一种新的 用于研究Tat作用机制的体外系统。 我们将使用 这些是为了研究 Tat 如何增加转录延伸和 启动。 HTLV Tax 和 HBV pX 是有效病毒传播所必需的 转录和复制，也是核癌蛋白。 超过 在过去一段时间的资助中，我们发现税收极大地增加了 多种细胞蛋白的 DNA 结合活性，这些蛋白含有 碱性区域-亮氨酸拉链 (bZIP) DNA 结合域。 此外，我们 已经表明税收承认 bZIP 的保守基本区域 促进二聚化，从而增加 DNA 结合。 没想到的是， Tax=-bZIP 复合物的 DNA 结合特异性与 单独的 bZIP。 值得注意的是，我们发现了 HBV pX，它不是 与税收同源，功能类似。 建议进行实验 进一步详细研究 Tax 和 pX 如何调节 bZIP DNA 结合并 确定该机制与病毒复制的关系 转变。 最后，在我们的研究过程中我们发现 一种新颖的细胞活性，如 Tax 和 pX，可增加 DNA 结合 细胞 bZIP 蛋白的活性。 这个细胞因素，我们指的是 作为 bZIP 增强因子 (BEF)，可能作为细胞辅助因子 税收和 pX。 我们将分离 BEF 的 cDNA 克隆，并用它来研究其 在病毒基因表达和转化中的作用。

Replication of animal viruses is dependent upon numerous components that are provided by the cell. For example, the transcription of viral genes requires cellular general transcription factors as well as certain sequence-specific DNA binding proteins. Typically, animal viruses encode regulatory proteins that function through cellular transcription factors to preferentially express viral genes. A knowledge of how these viral regulatory proteins function is essential for understanding viral replication and may suggest possibilities for therapeutic intervention. We have been studying the mechanisms by which the transcriptional regulatory proteins of three pathogenic viruses activate transcription: the Tat protein of human immunodeficiency virus (HIV), the Tax protein f human T- cell leukemia virus (HTLV), and the pX protein of hepatitis B virus (HBV). The HIV Tat protein is essential for viral replication and acts in a unique fashion; it binds to nascent HIV RNA to increase both transcription initiation and elongation. Over the past period of funding we have defined minimal components required for Tat-responsiveness and have developed a new in vitro system for studying the mechanism of Tat action. We will use these to study how Tat can increase both transcription elongation and initiation. HTLV Tax and HBV pX are required for efficient viral transcription and replication, and are also nuclear oncoproteins. Over the past period of funding we have found that Tax dramatically increases the DNA binding activity of a wide variety of cellular proteins that contain a basic region-leucine zipper (bZIP) DNA binding domain. Furthermore, we have show that Tax recognizes the conserved basic region of bZIPs to promote dimerization and thereby increase DNA binding. Unexpectedly, the DNA binding specificity of the Tax=-bZIP complex is different from that of the bZIP alone. Remarkably, we have discovered that HBV pX, which is not homologous to Tax, functions analogously. Experiments are proposed to study in further detail how Tax and pX modulate bZIP DNA binding and to determine the relationship of this mechanism to viral replication and transformation. Finally, ina the course of our studies we have discovered a novel cellular activity that, like Tax and pX, increases the DNA binding activity of cellular bZIP proteins. This cellular factor, which we refer to as bZIP Enhancing Factor (BEF), may function as a cellular co-factor for Tax and pX. We will isolate a cDNA clone for BEF and use this to study its role in viral gene expression and transformation.