Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.
Retrovirology. 2012 Jul 24;9:59. doi: 10.1186/1742-4690-9-59.
The TAR hairpin is present at both the 5' and 3' end of the HIV-1 RNA genome. The 5' element binds the viral Tat protein and is essential for Tat-mediated activation of transcription. We recently observed that complete TAR deletion is allowed in the context of an HIV-1 variant that does not depend on this Tat-TAR axis for transcription. Mutations that open the 5' stem-loop structure did however affect the leader RNA conformation and resulted in a severe replication defect. In this study, we set out to analyze which step of the HIV-1 replication cycle is affected by this conformational change of the leader RNA.
We demonstrate that opening the 5' TAR structure through a deletion in either side of the stem region caused aberrant dimerization and reduced packaging of the unspliced viral RNA genome. In contrast, truncation of the TAR hairpin through deletions in both sides of the stem did not affect RNA dimer formation and packaging.
These results demonstrate that, although the TAR hairpin is not essential for RNA dimerization and packaging, mutations in TAR can significantly affect these processes through misfolding of the relevant RNA signals.
TAR 发夹存在于 HIV-1 RNA 基因组的 5' 和 3' 末端。5' 元件结合病毒 Tat 蛋白，对于 Tat 介导的转录激活至关重要。我们最近观察到，在不依赖 Tat-TAR 轴进行转录的 HIV-1 变体中，完全缺失 TAR 是允许的。然而，打开 5' 茎环结构的突变会影响前导 RNA 构象，并导致严重的复制缺陷。在这项研究中，我们着手分析前导 RNA 构象变化影响 HIV-1 复制周期的哪个步骤。
我们证明，通过在茎区两侧的缺失打开 5' TAR 结构会导致异常的二聚化，并减少未剪接的病毒 RNA 基因组的包装。相比之下，通过在茎的两侧缺失来截断 TAR 发夹不会影响 RNA 二聚体的形成和包装。
这些结果表明，尽管 TAR 发夹对于 RNA 二聚体和包装不是必需的，但 TAR 中的突变可以通过相关 RNA 信号的错误折叠显著影响这些过程。
