CONTROL OF PAPILLOMAVIRUS LATE TRANSCRIPTION

乳头瘤病毒可引起鳞状细胞癌的良性和恶性病变 高等脊椎动物的上皮细胞。这些病毒的完整裂解周期 (包括晚期基因表达)仅在分化的细胞中发生 鳞状上皮。培养中的恶性病变和感染细胞 不会产生病毒。我们使用了牛乳头瘤病毒1型(bpv-L)作为 研究乳头瘤病毒晚期转录及其功能的模型系统 控制力。转录图谱数据表明，这些mRNAs 编码主要衣壳蛋白和次要衣壳蛋白，表达自 强病毒转录启动子(称为晚期启动子) 仅在生产性感染的上皮细胞中有效。我们的研究还包括 表明有多种机制可以抑制BPV-1的迟发 非生产性感染细胞中的转录。核径流分析 在转化的C127细胞中BPV-1转录的结果表明 BPV-1基因组的转录减弱了十倍以上 在早期和晚期的聚腺苷酸化位点之间，有效地有利于 使用早期的聚腺苷酸化位点而不是晚期的聚腺苷酸化位点。一个 BPV-1基因组转化的一系列细胞系 已经建立了后期区域来识别顺式元件 负责转录终止。表达载体还具有 被用来识别BPV-1晚期中的两个负调控元件 区域。一个元素已被映射到晚期区域的5‘部分。 该元素的作用机制目前正在研究中。一个 第二个负面调控因素已被映射到3‘末期 非翻译区，并抑制异源基因的表达 克隆到该基因的3‘非翻译区。这个元素最多 可能通过以下方式抑制非生产性感染细胞中的晚期基因表达 选择性地破坏晚期mRNA的稳定。有几种方法被用来 确认这一模型，并确定晚期mRNA稳定性是否受到调控 在角质形成细胞分化过程中。

The papillomaviruses cause benign and malignant lesions of squamous epithelia in higher vertebrates. The complete lytic cycle of these viruses (including late gene expression) occurs only in the differentiated cells of the squamous epithelium. Malignant lesions and infected cells in culture do not produce virus. We have used bovine papillomavirus type 1 (BPV-l) as a model system for the study of papillomavirus late transcription and its control. Transcriptional mapping data indicates that the mRNAs, which encode both the major and minor capsid proteins, are expressed from a strong viral transcriptional promoter (called the late promoter) which is active only in productively infected epithelium. Our studies have also shown that there are multiple mechanisms which inhibit BPV-1 late transcription in nonproductively infected cells. Nuclear run-off analysis of BPV-1 transcription in transformed C127 cells indicates that transcription of the BPV-1 genome is attenuated greater than tenfold between the early and late polyadenylation sites, effectively favoring the use of the early polyadenylation site over the late polyadenylation site. A series of cell lines transformed by BPV-1 genomes containing mutations in the late region have been established to identify the cis elements responsible for transcription termination. Expression vectors have also been used to identify two negative regulatory elements in the BPV-1 late region. One element has been mapped to the 5' portion of the late region. The mechanism of action of this element is currently under investigation. A second negative regulatory element has been mapped to the late 3' untranslated region and inhibits the expression of a heterologous gene when cloned into the 3' untranslated region of that gene. This element most likely inhibits late gene expression in nonproductively infected cells by selectively destabilizing late mRNAs. Several approaches are being used to confirm this model and to determine if late mRNA stability is regulated during keratinocyte differentiation.