Department of Oncology, Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada.
J Virol. 2011 Oct;85(19):10048-57. doi: 10.1128/JVI.00643-11. Epub 2011 Jul 20.
The human papillomavirus (HPV) E7 oncoprotein exists as a dimer and acts by binding to many cellular factors, preventing or retargeting their function and thereby making the infected cell conducive for viral replication. Dimerization of E7 is attributed primarily to the C-terminal domain, referred to as conserved region 3 (CR3). CR3 is highly structured and is necessary for E7's transformation ability. It is also required for binding of numerous E7 cellular targets. To systematically analyze the molecular mechanisms by which HPV16 E7 CR3 contributes to carcinogenesis, we created a comprehensive panel of mutations in residues predicted to be exposed on the surface of CR3. We analyzed our novel collection of mutants, as well as mutants targeting predicted hydrophobic core residues of the dimer, for the ability to dimerize. The same set of mutants was also assessed functionally for transformation capability in a baby rat kidney cell assay in conjugation with activated ras. We show that some mutants of HPV16 E7 CR3 failed to dimerize yet were still able to transform baby rat kidney cells. Our results identify several novel E7 mutants that abrogate transformation and also indicate that E7 does not need to exist as a stable dimer in order to transform cells.
人乳头瘤病毒（HPV）E7 癌蛋白以二聚体的形式存在，并通过与许多细胞因子结合发挥作用，从而阻止或重新靶向它们的功能，使受感染的细胞有利于病毒复制。E7 的二聚化主要归因于 C 末端结构域，称为保守区 3（CR3）。CR3 高度结构化，是 E7 转化能力所必需的。它也是结合许多 E7 细胞靶标的必要条件。为了系统分析 HPV16 E7 CR3 促进致癌作用的分子机制，我们在预测暴露于 CR3 表面的残基上创建了一个全面的突变面板。我们分析了我们新收集的突变体，以及针对二聚体预测的疏水区残基的突变体，以确定它们的二聚化能力。同样的突变体集还与激活的 ras 一起在幼鼠肾细胞测定中评估了其转化能力。我们表明，一些 HPV16 E7 CR3 的突变体无法二聚化，但仍然能够转化幼鼠肾细胞。我们的结果确定了几个新的 E7 突变体，这些突变体可消除转化作用，并且表明 E7 不需要以稳定的二聚体形式存在即可转化细胞。
