TRANSCRIPTION ANALYSIS OF THE SV40 EARLY AND LATE PROMOTER

人乳多空病毒，JCV，与人类 进行性多灶性脱髓鞘疾病 脑白质病 在组织培养中，病毒主要 仅限于在原代人胎儿神经胶质细胞中生长。 在这 在这项研究中，我们证明了病毒宿主的两个水平的调节 范围 早期JCV mRNA的表达，其编码 重要的病毒蛋白，大肿瘤抗原（T抗原），取决于 组织对早期增强子/启动子元件的识别- 在人类和啮齿类动物神经胶质细胞中发现的特定因子。 在 存在JCV T抗原时，病毒DNA复制需要 物种特异性因子，可能是DNA的一种成分 聚合酶，这是发现在广泛的灵长类动物细胞。 我们 进一步证明猿猴病毒40 T抗原具有足够的 同源性，有效替代类似的JCV蛋白 启动病毒DNA复制。 我们使用了底漆 JC病毒5 '-末端的延伸和S1分析 (JCV)早期RNA在感染的原代人神经胶质细胞在不同的 在稳定的JCV转化仓鼠胎仔中 神经胶质细胞 在感染后早期（1-5天），两个早期 转录物起始于核苷酸5122和5082。 一个主要 在以后的时间5 '-末端的移动导致合成新的 从核苷酸35开始的一系列早期mRNA， 在核苷酸5047、5037、AD 5012下游。 在 然而，转化的仓鼠细胞，仅在RNA种类上， 检测到，从核苷酸5122开始。 的机制 裂解过程中JCV早期RNA起始位点的转移 感染仍不清楚，但似乎类似于 发生在SV 40裂解周期中。 由于这种转变发生在DNA 当T抗原处于最高水平时， 与JCV DNA结合的T抗原和/或 染色质结构有助于这一事件。

Human papovavirus, JCV, is associated with the human demyelinating disorder progressive multifocal leukoencephalopathy. In tissue culture, the virus is largely restricted to growth in primary human fetal glial cells. In this study, we demonstrate two levels of regulation of the viral host range. Expression of early JCV mRNA, which encodes the essential viral protein, large tumor antigen (T-antigen), depends on recognition of the early enhancer/promoter elements by tissue- specific factors found in both human and rodent glial cells. In the presence of JCV T-antigen, viral DNA replication requires a species-specific factor, presumably a component of DNA polymerase, which is found in a wide range of primate cells. We further demonstrated that simian virus 40 T-antigen has sufficient homology to efficiently substitute for the analogous JCV protein in initiating viral DNA replication. We have used primer extension and S1 analysis to localize the 5'-termini of JC virus (JCV) early RNAs in infected primary human glial cells at various times postinfection and in stable JCV-transformed hamster fetal glial cells. At early times postinfection (days 1-5), two early transcripts are initiated at nucleotides 5122 and 5082. A major shift in 5'-ends at later times results in the synthesis of a new series of early mRNAs beginning upstream at nucleotide 35 and downstream at nucleotides 5047, 5037, ad 5012. In the transformed hamster cells, however, only on RNA species was detected, starting at nucleotide 5122. The mechanism underlying the shift in the initiation site of JCV early RNAs during a lytic infection remains unclear but appears analogous to that which occurs in the SV40 lytic cycle. Since the shift occurs during DNA replication, when T-antigen is at maximal levels, it is possible that T-antigen binding to JCV DNA and/or alterations in chromatin structure contribute to this event.