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Abstract：
The HIV-1 Gag protein playing a key role in HIV-1 viral assembly has recently been shown to interact through its nucleocapsid domain with the ribosomal protein L7 (RPL7) that acts as a cellular co-factor promoting Gag\'s nucleic acid (NA) chaperone activity. To further understand how the two proteins act together, we examined their mechanism individually and in concert to promote the annealing between dTAR, the DNA version of the viral transactivation element and its complementary cTAR sequence, taken as model HIV-1 sequences. Gag alone or complexed with RPL7 was found to act as a NA chaperone that destabilizes cTAR stem-loop and promotes its annealing with dTAR through the stem ends via a two-step pathway. In contrast, RPL7 alone acts as a NA annealer that through its NA aggregating properties promotes cTAR/dTAR annealing via two parallel pathways. Remarkably, in contrast to the isolated proteins, their complex promoted efficiently the annealing of cTAR with highly stable dTAR mutants. This was confirmed by the RPL7-promoted boost of the physiologically relevant Gag-chaperoned annealing of (+)PBS RNA to the highly stable tRNALys3 primer, favoring the notion that Gag recruits RPL7 to overcome major roadblocks in viral assembly.
摘要：
在HIV-1病毒组装中起关键作用的HIV-1Gag蛋白最近已显示通过其核衣壳结构域与核糖体蛋白L7（RPL7）相互作用，该蛋白作为细胞辅助因子促进Gag的核酸（NA）伴侣活性。为了进一步了解这两种蛋白质是如何一起起作用的，我们单独和一致地检查了它们的机制，以促进dTAR之间的退火，病毒反式激活元件的DNA版本及其互补的cTAR序列，作为模型HIV-1序列。发现单独或与RPL7复合的Gag充当NA伴侣，使cTAR茎环不稳定，并通过两步途径通过茎末端促进其与dTAR的退火。相比之下,RPL7单独充当NA退火剂,其通过其NA聚集性质经由两个平行途径促进cTAR/dTAR退火。值得注意的是,与分离的蛋白质相反，它们的复合物有效地促进了cTAR与高度稳定的dTAR突变体的退火。RPL7促进的（+）PBSRNA与高度稳定的tRNALys3引物的生理相关Gag伴侣退火的增强证实了这一点，赞成Gag招募RPL7以克服病毒组装中的主要障碍的想法。
