Charles Sturt University, School of Biomedical Sciences, Wagga Wagga, 2678, Australia.
Sci Rep. 2017 May 10;7(1):1650. doi: 10.1038/s41598-017-01853-7.
HIV-1 has caused 35 million deaths globally, and approximately the same number is currently living with HIV-1. The trans-activator of transcription (Tat) protein of HIV-1 plays an important regulatory function in the virus life cycle, responsible for regulating the reverse transcription of the viral genome RNA. Tat is found in the nucleus of infected cells, but can also invade uninfected neighbouring cells. Regions within Tat responsible for these cellular localisations are overlapping and include a nuclear localisation signal (NLS) spanning GRKKRR, and a cell penetrating peptide (CPP) signal spanning GRKKRRQRRRAPQN. However, the mechanism by which this NLS/CPP region mediates interaction with the nuclear import receptors remains to be resolved structurally. Here, we establish that the HIV-1 Tat:NLS/CPP is able to form a stable and direct interaction with the classical nuclear import receptor importin-α and using x-ray crystallography, we have determined the molecular interface and binding determinants to a resolution of 2.0 Å. We show for the first time that the interface is the same as host factors such as Ku70 and Ku80, rather than other virus proteins such as Ebola VP24 that bind on the outer surface of importin-α.
HIV-1 已在全球造成 3500 万人死亡，目前大约有同样数量的人携带 HIV-1。HIV-1 的转录反式激活蛋白（Tat）在病毒生命周期中发挥着重要的调节功能，负责调节病毒基因组 RNA 的逆转录。Tat 存在于受感染细胞的核内，但也可以侵入未感染的邻近细胞。Tat 中负责这些细胞定位的区域是重叠的，包括一个跨越 GRKKRR 的核定位信号（NLS）和一个跨越 GRKKRRQRRRAPQN 的细胞穿透肽（CPP）信号。然而，NLS/CPP 区域介导与核输入受体相互作用的机制在结构上仍有待解决。在这里，我们确定 HIV-1 Tat:NLS/CPP 能够与经典的核输入受体 importin-α 形成稳定且直接的相互作用，并通过 X 射线晶体学，我们已经确定了分子界面和结合决定因素，分辨率为 2.0Å。我们首次表明，该界面与宿主因子如 Ku70 和 Ku80 相同，而不是其他病毒蛋白，如结合在 importin-α 外表面的埃博拉病毒 VP24。
