Laboratory of Experimental Virology, Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.
Laboratory of Experimental Virology, Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.
Virus Res. 2018 May 2;250:51-64. doi: 10.1016/j.virusres.2018.04.008. Epub 2018 Apr 11.
For the production of viral genomic RNA, HIV-1 is dependent on an early viral protein, Tat, which is required for high-level transcription. The quantity of viral RNA detectable in blood of HIV-1 infected individuals varies dramatically, and a factor involved could be the efficiency of Tat protein variants to stimulate RNA transcription. HIV-1 virulence, measured by set-point viral load, has been observed to increase over time in the Netherlands and elsewhere. Investigation of tat gene evolution in clinical isolates could discover a role of Tat in this changing virulence. A dataset of 291 Dutch HIV-1 subtype B tat genes, derived from full-length HIV-1 genome sequences from samples obtained between 1985-2012, was used to analyse the evolution of Tat. Twenty-two patient-derived tat genes, and the control Tat were analysed for their capacity to stimulate expression of an LTR-luciferase reporter gene construct in diverse cell lines, as well as for their ability to complement a tat-defective HIV-1 clone. Analysis of 291 historical tat sequences from the Netherlands showed ample amino acid (aa) variation between isolates, although no specific mutations were selected for over time. Of note, however, the encoded protein varied its length over the years through the loss or gain of stop codons in the second exon. In transmission clusters, a selection against the shorter Tat86 ORF was apparent in favour of the more common Tat101 version, likely due to negative selection against Tat86 itself, although random drift, transmission bottlenecks, or linkage to other variants could also explain the observation. There was no correlation between Tat length and set-point viral load; however, the number of non-intermediate variants in our study was small. In addition, variation in the length of Tat did not significantly change its capacity to stimulate transcription. From 1985 till 2012, variation in the length of the HIV-1 subtype B tat gene is increasingly found in the Dutch epidemic. However, as Tat proteins did not differ significantly in their capacity to stimulate transcription elongation in vitro, the increased HIV-1 virulence seen in recent years could not be linked to an evolving viral Tat protein.
为了生产病毒基因组 RNA，HIV-1 依赖于一种早期病毒蛋白 Tat，它是高水平转录所必需的。HIV-1 感染者血液中可检测到的病毒 RNA 数量差异很大，一个涉及的因素可能是 Tat 蛋白变体刺激 RNA 转录的效率。HIV-1 的毒力，用设定点病毒载量来衡量，已经在荷兰和其他地方观察到随着时间的推移而增加。对临床分离株中 tat 基因进化的研究可能会发现 Tat 在这种毒力变化中的作用。使用从 1985 年至 2012 年期间获得的样本中提取的全长 HIV-1 基因组序列，对 291 个荷兰 HIV-1 亚型 B tat 基因进行了分析，以研究 Tat 的进化。对 22 个患者衍生的 tat 基因和对照 Tat 进行了分析，以研究它们在不同细胞系中刺激 LTR-荧光素酶报告基因构建体表达的能力，以及它们补充 tat 缺陷型 HIV-1 克隆的能力。对来自荷兰的 291 个历史 tat 序列的分析表明，尽管随着时间的推移没有选择特定的突变，但分离株之间的氨基酸（aa）变化很大。然而，值得注意的是，编码蛋白在多年来通过在第二外显子中丢失或获得终止密码子而改变其长度。在传播群中，明显选择了较短的 Tat86 ORF，有利于更常见的 Tat101 版本，这可能是由于对 Tat86 本身的负选择，尽管随机漂移、传播瓶颈或与其他变体的连锁也可以解释这一观察结果。Tat 长度与设定点病毒载量之间没有相关性；然而，我们研究中的非中间变体数量较少。此外，Tat 长度的变化并没有显著改变其刺激转录的能力。从 1985 年到 2012 年，荷兰流行的 HIV-1 亚型 B tat 基因长度的变化越来越多。然而，由于 Tat 蛋白在体外刺激转录延伸的能力没有显著差异，近年来观察到的 HIV-1 毒力增加不能与进化中的病毒 Tat 蛋白联系起来。
