Kitasato H, Hillova J, Lenormand M, Hill M
Laboratory of Cellular and Molecular Biology, C.N.R.S., Institute of Cancer and Immunogenetics, Villejuif, France.
Anticancer Res. 1991 May-Jun;11(3):1165-72.
Human papillomavirus type 33 (HPV33) belongs to the group of HPV types frequently found in severe cervical dysplasias and carcinomas. By analogy with HPV types 16 and 18 selectively expressing E6 and E7 genes in malignant tissues, we studied the HPV33 E6 and E7 open reading frames in various configurations with upstream promoter and noncoding region (NCR) known to contain a particular 78-bp tandem repeat. HPV DNA fragments were cloned into expression vectors between the SV40 or the mouse metallothionein I promoter and the neo gene, transfected into NIH3T3 cells, selected by neo resistance, and inoculated into nude mice. In these bioassays, a weak transforming activity was detected for E6 open reading frame, and could be significantly enhanced either by the NCR or the E7 open reading frame. No tumorigenicity could be detected for E7 alone or in configuration with the upstream NCR. Further analyses of tumor cells showed that HPV33-derived genes were not sufficient to induce an anchorage-independent phenotype and, interstingly, there was no requirement for virus-transfected tumor cells to retain HPV sequences during tumor progression. We concluded that the transformation function of HPV33 resides in E6 gene as assayed by tumorigenicity. An enhancer of the E6 promoter is located in the NCR. On the other hand, in the absence of the NCR, E6 tumorigenicity may be augmented by the E7.
人乳头瘤病毒33型（HPV33）属于在严重宫颈发育异常和癌组织中经常发现的HPV类型组。类似于在恶性组织中选择性表达E6和E7基因的HPV16和18型，我们研究了HPV33 E6和E7开放阅读框的各种构型，其上游启动子和已知包含特定78碱基对串联重复序列的非编码区（NCR）。HPV DNA片段被克隆到SV40或小鼠金属硫蛋白I启动子与新霉素基因之间的表达载体中，转染到NIH3T3细胞中，通过新霉素抗性进行筛选，然后接种到裸鼠体内。在这些生物测定中，检测到E6开放阅读框具有弱转化活性，并且可以通过NCR或E7开放阅读框显著增强。单独的E7或与上游NCR组合时均未检测到致瘤性。对肿瘤细胞的进一步分析表明，HPV33衍生的基因不足以诱导不依赖贴壁的表型，有趣的是，在肿瘤进展过程中，病毒转染的肿瘤细胞不需要保留HPV序列。我们得出结论，通过致瘤性测定，HPV33的转化功能存在于E6基因中。E6启动子的增强子位于NCR中。另一方面，在没有NCR的情况下，E7可能会增强E6的致瘤性。
