Regulation of Foamy Virus Protease Activity by Viral RNA: a Novel and Unique Mechanism among Retroviruses
Regulation of Foamy Virus Protease Activity by Viral RNA: a Novel and Unique Mechanism among Retroviruses
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DOI：
10.1128/jvi.02211-10
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发表时间：
2011-05-01
影响因子：
5.4
通讯作者：
Woehrl, Birgitta M.
中科院分区：
文献类型：
--
作者：
Hartl, Maximilian J.;Bodem, Jochen;Woehrl, Birgitta M.
泡沫病毒（FVs）从一个特定的转录物合成Pol前体蛋白。因此，与人类免疫缺陷病毒等正转录酶病毒所发现的相反，Gag-Pol前体蛋白不合成。泡沫状病毒Pol由蛋白酶（PR）结构域、逆转录酶结构域和整合酶结构域组成，并被加工成成熟的蛋白酶-逆转录酶（PR- rt）融合蛋白和整合酶。为了避免在病毒组装前过早地进行Gag和Pol加工，必须严格调节蛋白酶活性。我们最近证明了FV蛋白酶是一种非活性单体，具有非常弱的二聚化倾向，并假设蛋白酶通过二聚化激活。在这里，我们发现了一个位于病毒RNA pol区的特异性蛋白酶激活RNA基序（PARM），它在体外和体内刺激PR活性，揭示了一种新的独特的逆转录病毒蛋白酶激活机制。这种机制与正转录酶病毒的机制截然不同，在逆转录酶病毒中，即使在病毒样颗粒组装过程中没有病毒RNA的情况下，蛋白酶也能被激活。虽然已经证明整合酶结构域对Pol摄取很重要，但泡沫病毒蛋白酶的激活是与整合酶无关的。我们发现至少有两个泡沫状的病毒PR-RT分子与PARM结合，只有含有PARM的rna导致蛋白酶的显著激活。含有PARM的DNA不能激活蛋白酶。通过引物延伸（SHAPE）分析选择性2′羟基酰化对PARM结构的测定，发现其具有独特的RNA折叠，这对蛋白酶激活和病毒成熟很重要。
Foamy viruses (FVs) synthesize the Pol precursor protein from a specific transcript. Thus, in contrast to what was found for orthoretroviruses, e.g., human immunodeficiency virus, no Gag-Pol precursor protein is synthesized. Foamy viral Pol consists of a protease (PR) domain, a reverse transcriptase domain, and an integrase domain and is processed into a mature protease-reverse transcriptase (PR-RT) fusion protein and the integrase. Protease activity has to be strictly regulated in order to avoid premature Gag and Pol processing before virus assembly. We have demonstrated recently that FV protease is an inactive monomer with a very weak dimerization tendency and postulated protease activation through dimerization. Here, we identify a specific protease-activating RNA motif (PARM) located in the pol region of viral RNA which stimulates PR activity in vitro and in vivo, revealing a novel and unique mechanism of retroviral protease activation. This mechanism is strikingly different to that of orthoretroviruses, where the protease can be activated even in the absence of viral RNA during the assembly of virus-like particles. Although it has been shown that the integrase domain is important for Pol uptake, activation of the foamy virus protease is integrase independent. We show that at least two foamy virus PR-RT molecules bind to the PARM and only RNAs containing the PARM result in significant activation of the protease. DNA harboring the PARM is not capable of protease activation. Structure determination of the PARM by selective 2' hydroxyl acylation analyzed by primer extension (SHAPE) revealed a distinct RNA folding, important for protease activation and thus virus maturation.