Angulo A, Messerle M, Koszinowski U H, Ghazal P
Departments of Immunology and Molecular Biology, Division of Virology, The Scripps Research Institute, La Jolla, California 92037, USA.
J Virol. 1998 Nov;72(11):8502-9. doi: 10.1128/JVI.72.11.8502-8509.1998.
The cytomegalovirus (CMV) enhancer is a highly complex regulatory region containing multiple elements that interact with a variety of host-encoded transcription factors. Many of these sequence elements are conserved among the different species strains of CMV, although the arrangement of the various elements and overall sequence composition of the CMV enhancers differ remarkably. To delineate the importance of this region to a productive infection and to explore the possibility of generating a murine CMV (MCMV) under the control of human CMV (HCMV) genetic elements, the MCMV enhancer was resected and replaced either with nonregulatory sequences or with paralogous sequences from HCMV. The effects of these various deletions and substitutions on viral growth in transfected or infected tissue-culture cells were evaluated. We found that mutations in MCMV that eliminate or substitute for the enhancer with nonregulatory sequences showed a severe deficiency in virus synthesis. This growth defect is effectively complemented by the homologous MCMV enhancer as well as the HCMV enhancer. In the latter case, the chimeric viruses (hybrid MCMV strains) containing the molecularly shuffled human enhancer exhibit infectious kinetics similar to that of parental wild-type and wild-type revertant MCMV. These results also show that open reading frames m124, m124.1, and m125 located within the enhancer region are nonessential for growth of MCMV in cells. Most importantly, we conclude that the enhancer of MCMV is required for optimal infection and that its diverged human counterpart can advantageously replace its role in promoting viral infectivity.
巨细胞病毒（CMV）增强子是一个高度复杂的调控区域，包含多个与多种宿主编码转录因子相互作用的元件。尽管CMV增强子中各种元件的排列和整体序列组成差异显著，但其中许多序列元件在CMV的不同物种毒株中是保守的。为了阐明该区域对有效感染的重要性，并探索在人巨细胞病毒（HCMV）遗传元件控制下产生鼠巨细胞病毒（MCMV）的可能性，切除了MCMV增强子，并用非调控序列或HCMV的同源序列进行替换。评估了这些不同的缺失和替换对转染或感染的组织培养细胞中病毒生长的影响。我们发现，MCMV中消除增强子或用非调控序列替代增强子的突变显示出病毒合成严重缺陷。这种生长缺陷可被同源的MCMV增强子以及HCMV增强子有效互补。在后一种情况下，含有分子重排的人增强子的嵌合病毒（杂交MCMV毒株）表现出与亲本野生型和野生型回复MCMV相似的感染动力学。这些结果还表明，位于增强子区域内的开放阅读框m124、m124.1和m125对MCMV在细胞中的生长并非必需。最重要的是，我们得出结论，MCMV的增强子是最佳感染所必需的，其分化的人对应物可以有利地取代其在促进病毒感染性方面的作用。
