IP6 is an HIV pocket factor that prevents capsid collapse and promotes DNA synthesis.
IP6 is an HIV pocket factor that prevents capsid collapse and promotes DNA synthesis.
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DOI：
10.7554/elife.35335
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发表时间：
2018-05-31
期刊：
影响因子：
7.7
通讯作者：
James LC
中科院分区：
文献类型：
--
作者：
Mallery DL;Márquez CL;McEwan WA;Dickson CF;Jacques DA;Anandapadamanaban M;Bichel K;Towers GJ;Saiardi A;Böcking T;James LC
HIV衣壳是半透性的，并覆盖着正电性孔，这些孔对于病毒DNA合成和感染是必不可少的。在这里，我们发现这些孔结合丰富的细胞聚阴离子IP 6，将病毒稳定性从几分钟转变为几小时，并允许新合成的DNA在衣壳内积累。孔内的精氨酸环与IP 6配位，其将衣壳六聚体增强了近10°C。单分子测量表明，这使得天然HIV衣壳高度稳定，并防止自发崩溃。此外，逆转录测定显示，一旦被IP 6稳定，衣壳内新病毒DNA的积累增加>100倍。值得注意的是，病毒生产细胞中肌醇的同位素标记揭示了HIV选择性地包装每个感染性病毒体超过300个IP 6分子。我们建议，HIV招募IP 6来调节衣壳稳定性和脱壳，类似于小核糖核酸病毒口袋因子。HIV-1/IP 6/衣壳/辅因子/逆转录。像HIV这样的病毒侵入细胞并复制它们的基因组以产生新的病毒。为了躲避我们免疫系统中在细胞内活跃的成分，HIV使用一种称为衣壳的蛋白质外壳，保护其基因组免受检测和破坏。然而，衣壳面临的工程挑战超出了即使是最复杂的人造结构所面临的挑战。这是因为衣壳必须足够强大，能够在细胞内存活数小时，但又不能强大到当病毒需要释放其基因组时无法快速打开。这一过程被称为“脱膜”，是艾滋病病毒生物学中尚未回答的重大问题之一。2016年，研究人员意外地发现，HIV衣壳上装饰着数百个孔：每个亚基的中心都有一个孔。每个孔包含一个由六个带正电荷的氨基酸组成的环，这些氨基酸应该会破坏衣壳的稳定性并使其分裂。然而，在各种各样的病毒上都发现了类似的孔。Mallery等人-包括参与2016年工作的几位研究人员-着手研究为什么HIV衣壳含有带正电荷的孔。初步实验表明，细胞中丰富的一种名为IP 6的分子可以与艾滋病毒衣壳结合。为此，IP 6中的六个带负电荷的磷酸基团与孔中的六个带正电荷的残基相匹配。在一项相关的研究中，马尔克斯等人开发了一种新方法，可以通过时间可视化单个衣壳的命运。在这里，Mallery等人使用该方法表明，IP 6增加了衣壳保持完整的时间，从几分钟到超过10小时。这使得HIV能够在衣壳内复制其基因组，这意味着在病毒准备产生新病毒时，它仍然受到保护。Mallery等人还表明，HIV在复制时会将300多个IP 6分子包装到自身中。其他称为小核糖核酸病毒的病毒使用称为口袋因子的小分子来稳定衣壳并触发脱壳。Mallery等人提出IP 6是HIV口袋因子。正如口袋因子的研究刺激了抗小核糖核酸病毒药物的开发一样，了解IP 6的作用可能有助于开发新的HIV治疗方法。
The HIV capsid is semipermeable and covered in electropositive pores that are essential for viral DNA synthesis and infection. Here, we show that these pores bind the abundant cellular polyanion IP6, transforming viral stability from minutes to hours and allowing newly synthesised DNA to accumulate inside the capsid. An arginine ring within the pore coordinates IP6, which strengthens capsid hexamers by almost 10°C. Single molecule measurements demonstrate that this renders native HIV capsids highly stable and protected from spontaneous collapse. Moreover, encapsidated reverse transcription assays reveal that, once stabilised by IP6, the accumulation of new viral DNA inside the capsid increases >100 fold. Remarkably, isotopic labelling of inositol in virus-producing cells reveals that HIV selectively packages over 300 IP6 molecules per infectious virion. We propose that HIV recruits IP6 to regulate capsid stability and uncoating, analogous to picornavirus pocket factors. HIV-1/IP6/capsid/co-factor/reverse transcription. Viruses like HIV invade cells and replicate their genome to create new viruses. To hide from components of our immune system that are active inside the cell, HIV uses a protein shell called a capsid, which protects its genome from detection and destruction. However, the capsid faces an engineering challenge beyond those faced by even the most complex man-made structures. This is because the capsid must be strong enough to survive for hours inside the cell but not so strong that it cannot quickly open when the virus needs to release its genome. How this process, called ‘uncoating’, is achieved is one of the great unanswered questions in HIV biology. In 2016, researchers made the unexpected discovery that the HIV capsid is decorated with hundreds of pores: one at the center of every subunit from which it is built. Each pore contains a ring of six positively charged amino acids that should destabilize the capsid and cause it to break apart. Yet similar pores are found on a diverse range of viruses. Mallery et al. – who include several of the researchers involved in the 2016 work – set out to investigate why the HIV capsid contains the positively charged pores. Initial experiments revealed that a molecule called IP6, which is abundant in cells, can bind to the HIV capsid. To do so, six negatively charged phosphate groups in IP6 match up with the six positively charged residues in the pore. In a related study, Márquez et al. developed a new method that allows the fate of individual capsids to be visualized through time. Here, Mallery et al. use the method to show that IP6 increases how long the capsid remains intact from several minutes to over 10 hours. This allows HIV to copy its genome inside the capsid, meaning it remains protected while the virus prepares to produce new viruses. Mallery et al. also show that HIV packages more than 300 IP6 molecules into itself when it replicates. Other viruses called picornaviruses use small molecules called pocket factors to stabilize the capsid and to trigger uncoating. Mallery et al. propose that IP6 is an HIV pocket factor. Just as studies of pocket factors have stimulated the development of anti-picornavirus drugs, understanding the role of IP6 may help to develop new treatments for HIV.