Analysis of the TRIM5α-mediated restriction of retrotransposons

TRIM5α 介导的逆转录转座子限制的分析

• 批准号: 416905780
• 负责人: Professor Dr. Thomas Gramberg
• 金额: --
• 依托单位: Virologisches Institut - Klinische und Molekulare Virologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/416905780?language=en
• 关键词: Analysis; TRIM5; mediated; restriction; retrotransposons

LINE-1 retrotransposons are the only autonomously active mobile genetic elements within the human genome. About 17 % of the human genome is of LINE origin and it still harbors about 100 potentially active copies. Although "jumping" of LINE-1 elements into new locations is rare, new LINE-1 insertions have been shown to cause severe genetic disorders, like hemophilia, muscular dystrophy, or cancer. The efficient control of transposable elements is therefore essential to maintain genome integrity. For the control of exogenous viral infections, cellular restriction factors are key. One of them, TRIM5α, has been shown to block various retroviruses in a species-specific manner, most likely by direct interaction with the retroviral capsid structure. While rhesus but not human TRIM5 alpha efficiently inhibits HIV-1 infection, we found that both rhesus and human TRIM5α restrict the retrotransposition of LINE-1 elements to a similar degree. This is even more surprising since intracellular replicating LINE-1 elements do not form a capsid structure, which is the classical target of the TRIM5 alpha-mediated block to retroviral infection. Thus, the inhibition of endogenous LINE-1 elements represents a novel function of the important HIV restriction factor TRIM5 alpha. Within Aim1 of this proposal, we will determine how human TRIM5a blocks endogenous LINE-1 elements and which steps of the life cycle of these elements are blocked. The block to endogenous genetic elements by TRIM5 alpha might also explain the strong positive selection of TRIM5α during evolution, which has been shown to predate the appearance of primate lentiviruses, like HIV-1. Several single nucleotide polymorphisms can be found in human TRIM5 alpha, but the only differ marginally in their ability to block HIV. Thus, within the second aim of this proposal we will ask whether the various TRIM5α alleles show a differential activity against human LINE-1. The murine genome contains a much larger number of still active endogenous retroviruses and retroelements compared to the human genome. Interestingly, the genetic locus of TRIM5 alpha also strongly expanded in mice and harbors seven different TRIM5 alpha orthologues, TRIM12a-c and TRIM30a-d. Since no virus driving this expansion has been identified so far, we will ask within the third aim of the study whether the abundance of endogenous retroviruses and retroelements in mice might be responsible for the expansion of the murine TRIM5 locus and determine the effect of the TRIM5 proteins on the replication of different endogenous retroviruses and retroelements. Together, this application will identify the mechanism how human TRIM5α blocks the replication of endogenous LINE-1 retroelements. Also, this project will clarify to what extent different alleles of human TRIM5 alpha and the different murine TRIM5 orthologues block retroelements and therefore contribute to genome stability in mice and men.

LINE-1反转录转座子是人类基因组中唯一自主活动的移动的遗传元件。大约17%的人类基因组是LINE起源的，它仍然含有大约100个潜在的活性拷贝。虽然LINE-1元件“跳跃”到新的位置是罕见的，但新的LINE-1插入已被证明会导致严重的遗传疾病，如血友病，肌肉萎缩症或癌症。因此，转座因子的有效控制对于维持基因组的完整性至关重要。对于控制外源性病毒感染，细胞限制因子是关键。其中之一，TRIM 5 α，已被证明以物种特异性方式阻断各种逆转录病毒，最有可能是通过与逆转录病毒衣壳结构直接相互作用。虽然恒河猴而不是人TRIM 5 α有效地抑制HIV-1感染，但我们发现恒河猴和人TRIM 5 α都以相似的程度限制LINE-1元件的逆转录转座。这甚至更令人惊讶，因为细胞内复制LINE-1元件不形成衣壳结构，而衣壳结构是TRIM 5 α介导的逆转录病毒感染阻断的经典靶标。因此，内源性LINE-1元件的抑制代表了重要的HIV限制因子TRIM 5 α的新功能。在本提案的Aim 1中，我们将确定人类TRIM 5a如何阻断内源性LINE-1元件以及这些元件生命周期的哪些步骤被阻断。TRIM 5 α对内源性遗传元件的阻断也可以解释TRIM 5 α在进化过程中的强阳性选择，这已被证明早于灵长类慢病毒（如HIV-1）的出现。在人类TRIM 5 α中可以发现几种单核苷酸多态性，但它们在阻断HIV的能力上仅有微小的差异。因此，在本提案的第二个目标中，我们将询问各种TRIM 5 α等位基因是否对人LINE-1表现出不同的活性。与人类基因组相比，鼠基因组含有大量仍有活性的内源性逆转录病毒和逆转录因子。有趣的是，TRIM 5 α的遗传基因座在小鼠中也强烈扩增，并含有七种不同的TRIM 5 α直系同源物，TRIM 12 a-c和TRIM 30 a-d。由于到目前为止还没有发现驱动这种扩增的病毒，因此我们将在本研究的第三个目的中询问小鼠中内源性逆转录病毒和逆转录因子的丰度是否可能导致小鼠TRIM 5基因座的扩增，并确定TRIM 5蛋白对不同内源性逆转录病毒和逆转录因子复制的影响。总之，本申请将确定人TRIM 5 α如何阻断内源性LINE-1逆转录元件复制的机制。此外，该项目将阐明人类TRIM 5 α的不同等位基因和不同的小鼠TRIM 5直系同源物在多大程度上阻断逆转录因子，从而有助于小鼠和男性的基因组稳定性。