Fischer N, Heinkelein M, Lindemann D, Enssle J, Baum C, Werder E, Zentgraf H, Müller J G, Rethwilm A
Institut für Virologie und Immunbiologie, Universität Würzburg, Germany.
J Virol. 1998 Feb;72(2):1610-5. doi: 10.1128/JVI.72.2.1610-1615.1998.
Subgenomic expression plasmids for the so-called human foamy virus (HFV) structural gag, gag/pol, and env genes were constructed and used to analyze foamy virus particle formation by electron microscopy. Expression of an R-U5-gag-pol construct under control of the human cytomegalovirus immediate-early enhancer-promoter resulted in the formation of viral cores with a homogeneous size of approximately 50 nm located in the cytoplasm. Upon coexpression of an envelope construct, particles were observed budding into cytoplasmic vesicles and from the plasma membrane. Expression of the Gag protein precursor pr74 alone led to aberrantly formed viral particles of heterogeneous size and with open cores. Normal-shaped cores were seen after transfection of a construct expressing the p70gag cleavage product, indicating that p70gag is able to assemble into capsids. Coexpression of p70gag and Env resulted in budding virions, ruling out a requirement of the reverse transcriptase for capsid or virion formation. In sharp contrast to other retroviruses, the HFV cores did not spontaneously bud from cellular membranes. Radiochemical labeling followed by protein gel electrophoresis also revealed the intracellular retention of Env-deprived HFV capsids.
构建了用于所谓人类泡沫病毒（HFV）结构gag、gag/pol和env基因的亚基因组表达质粒，并通过电子显微镜分析泡沫病毒颗粒的形成。在人巨细胞病毒立即早期增强子-启动子控制下的R-U5-gag-pol构建体的表达导致在细胞质中形成大小均匀约为50nm的病毒核心。在共表达包膜构建体时，观察到颗粒出芽进入细胞质囊泡并从质膜出芽。单独表达Gag蛋白前体pr74导致形成大小不均一且核心开放的异常形成的病毒颗粒。在转染表达p70gag裂解产物的构建体后可见正常形状的核心，表明p70gag能够组装成衣壳。p70gag和Env的共表达导致病毒粒子出芽，排除了逆转录酶对衣壳或病毒粒子形成的需求。与其他逆转录病毒形成鲜明对比的是，HFV核心不会从细胞膜自发出芽。放射性化学标记后进行蛋白质凝胶电泳也揭示了缺乏Env的HFV衣壳在细胞内的滞留。
