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。对转录调控的理解 乳头瘤病毒及其与上皮细胞控制的关系 为了阐明细胞分化的作用，细胞分化是必要的 乳头瘤病毒在癌症发生中的作用我们使用了牛乳头瘤病毒 I型(BPV-1)作为研究晚期转录和转录的模型系统 它的控制力。因为没有组织培养系统来支持晚期 转录，有必要分析发生在 牛纤维乳头状瘤本身。一个全长的cdna文库已经被 从牛双乳头状瘤组织中分离的Frm基因构建而成 产生了几个BPV-1特异的cDNA，在BPV-1转化的 C127细胞库。特别有趣的是，这些mRNA似乎是 从乳头状瘤特异性启动子转录而来。这一点已经得到了 引物延伸和核酸酶S1分析。“迟到”或 乳头状瘤特异性启动子的活性似乎高达100倍 而不是BPV-1转化细胞中用于转录的启动子。我们 目前正在尝试识别顺式和反式作用元件 它们参与了对晚期启动子的控制并确定 这些反式作用因子在上皮细胞中可能发挥的作用 差异化。对晚期转录的第二水平控制也 发生。分离的细胞核中发生转录的初步分析 从BPV-1转化的细胞中发现转录终止于 晚期聚腺苷酸化位点上游的晚期基因区域，有效地 阻止晚期mRNA的合成。我们目前正在尝试 确定哪些序列是转录终止所必需的 确定与这些序列反式作用的任何因素。

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. An understanding of the transcriptional regulation of the papillomaviruses and its relationship to the control of epithelial cell differentiation is necessary for the elucidation of the role of the papillomaviruses in carcinogenesis. We have used bovine papillomavirus type 1 (BPV-1) as a model system for the study of late transcription and its control. Since there are not tissue culture systems which support late transcription, it has been necessary to analyze transcription occurring in the bovine fibropapilloma itself. A full length cDNA library has been constructed frm mRNA isolated from bovine bifropapolloma tissue and has yielded several BPV-1-specific cDNAs not identified in a BPV-1-transformed C127 cell library. Of particular interest is that these mRNAs appear to be transcribed from a papilloma-specific promoter. This has been confirmed by primer extension and nuclease S1 analysis. The "late" or papilloma-specific promoter appears to be as much as 100-fold more active than the promoters used for transcription in BPV-1-transformed cells. We are currently attempting to identify the cis and trans-acting elements which are involved in the control of the late promoter and to determine the role which these trans-acting factors may play in epithelial cell differentiation. A second level of control of late transcription also occurs. Preliminary analysis of transcription occurring in nuclei isolated from BPV-1-transformed cells shows that transcription terminates in the late gene region upstream of the late polyadenylation site, effectively blocking the synthesis of late mRNAs. We are currently attempting to determine what sequences are necessary for transcription termination and to identify any factors which interact in trans with these sequences.