Carboxy-terminal cleavage of the human foamy virus Gag precursor molecule is an essential step in the viral life cycle
Carboxy-terminal cleavage of the human foamy virus Gag precursor molecule is an essential step in the viral life cycle
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DOI：
10.1128/jvi.71.10.7312-7317.1997
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发表时间：
1997-10-01
影响因子：
5.4
通讯作者：
Rethwilm, A
中科院分区：
文献类型：
--
作者：
Enssle, J;Fischer, N;Rethwilm, A
泡沫病毒（FVs）表达Gag蛋白作为分子量为74 kDa（pr 74）的前体，其中70-kDa蛋白（p70）被病毒蛋白酶切割。为了更好地理解FV Gag蛋白的加工和功能，我们已经产生并分析了感染性分子克隆的C-末端gag区域的突变体，我们的研究结果表明，p70是一个N-末端切割产物的pr 74。然而，我们无法鉴定p4分子。发现仅表达p70的病毒突变体具有复制能力，尽管滴度与野生型病毒相比。一个强烈的倾向，以合成和切割pr 74分子推导出从出现的回复突变体转染后，这种突变体，取代的p6（gag）结构域的人类免疫缺陷病毒1型的p4结构域的FV导致在一个稳定的嵌合病毒复制滴度比野生型病毒低10倍。FV Gag蛋白的丝氨酸残基被磷酸化，突变pI结构域中保守的丝氨酸对病毒在细胞培养中的复制没有影响。发现p70/p74 Gag切割是病毒感染性所需的，因为假定切割位点的诱变导致无复制能力的病毒。同时，裂解位点突变体在病毒体DNA的细胞内cDNA合成中存在缺陷，这表明正确的FV颗粒形成和病毒体DNA的产生在功能上是相关的。
Foamy viruses (FVs) express the Gag protein as a precursor with a molecular mass of 74 kDa (pr74) from which a 70-kDa protein (p70) is cleaved by the viral protease, To gain a better understanding of FV Gag protein processing and function, we have generated and analyzed mutants in the C-terminal gag region of an infectious molecular clone, Our results show that p70 is an N-terminal cleavage product of pr74. However, we were unable to identify a p4 molecule. A virus mutant expressing p70 only was found to be replication competent, albeit at titers compared to those of wild-type virus. A strong tendency to synthesize and cleave a pr74 molecule was deduced from the occurrence of revertants upon transfection of this mutant, Substitution of the p6(gag) domain of human immunodeficiency virus type 1 for the p4 domain of FV resulted in a stable chimeric virus which replicated to titers 10 times lower than those of wild-type virus. FV Gag protein was found to be phosphorylated at serine residues, Mutagenesis of serines conserved in the pi domain had no influence on viral replication in cell culture. The p70/p74 Gag cleavage was found to be required for viral infectivity, since mutagenesis of the putative cleavage site led to replication-incompetent virus. Interestingily, the cleavage site mutants were defective in the intracellular cDNA synthesis of virion DNA, which indicates that correct FV particle formation and the generation of virion DNA are functionally linked.