Reversal of epigenetic silencing rescues integrase-deficient HIV-1 replication

摘要 在细胞质中逆转录后，逆转录病毒DNA裸露进入细胞核， 被目前未知的先天免疫因子感染，并被抑制性染色质覆盖。然而，逆转录病毒 编码整合酶（IN），其允许前病毒DNA插入到前病毒的转录活性区域中。 宿主基因组，然后导致逆转录病毒DNA上的抑制性染色质标记被替换为 侧翼宿主染色质的活性标记特征。如果IN活性通过诱变或通过 药物，那么未整合的逆转录病毒DNA仍然被抑制性染色质覆盖， 沉默这项拨款有两个目标。首先，我假设，如果未整合的HIV-1 DNA 那么就有可能激活该DNA，拯救IN-HIV-1的复制， 通过直接激活HIV-1 LTR启动子和/或通过直接逆转表观遗传沉默。我们 现在已经表明，HTLV-1 Tax蛋白的表达，细胞NK-kB/Rel转录的有效激活剂， 因子，诱导RelA和RelB募集到HIV-1 LTR中存在的NF-κ B位点， 或逆转未整合的HIV-1 DNA的表观遗传沉默，使IN-HIV-1突变体能够建立一个强大的， 在CEM-SS细胞中传播感染。目前尚不清楚HIV-1 LTR的转录激活是否与HIV-1的转录水平有关。 发生在病毒DNA上的表观遗传标记发生变化之前或之后，这是我们希望解决的问题， 包括在原代T细胞中。我们现在报告在293 T细胞中获得的初步数据，表明HSV-1 ICP 0蛋白还可以拯救IN- HIV-1基因表达，在这种情况下，通过明显地直接调节 未整合的HIV-1 DNA的表观遗传状态。我们的目标是将这种分析扩展到T细胞，看看ICP 0是否确实是 通过与Tax不同的机制拯救IN- HIV-1基因表达。最后，虽然认识到 和沉默IN-MLV已被Goff实验室确定为HUSH复合物， NP 220，我们表明这些因子不是沉默IN-HIV-1所必需的。因此，该应用程序的一个关键目标是 进行无偏见的CRISPR/Cas基因筛选，以确定人类先天免疫因子， 这一任务，然后确定其作用机制。

ABSTRACT After reverse transcription in the cytoplasm, retroviral DNAs enter the nucleus naked and are then detected by currently unknown innate immune factors and coated with repressive chromatin. However, retroviruses encode an integrase (IN) which allows the proviral DNA to be inserted into transcriptionally active areas of the host genome, which then results in the repressive chromatin marks on the retroviral DNA being replaced by the active marks characteristic of the flanking host chromatin. If IN activity is blocked either by mutagenesis or by a drug, then the unintegrated retroviral DNA remains covered with inhibitory chromatin and is transcriptionally silenced. This grant proposes has two goals. Firstly, I hypothesize that if unintegrated HIV-1 DNA is epigenetically silenced then it should be possible to activate that DNA, and rescue the replication of IN- HIV-1, by either directly activating the HIV-1 LTR promoter and/or by directly reversing the epigenetic silencing. We have now shown that expression of the HTLV-1 Tax protein, a potent activator of cellular NK-kB/Rel transcription factors, induces the recruitment of RelA and RelB to the NF-kB sites present in the HIV-1 LTR and also prevents or reverses the epigenetic silencing of unintegrated HIV-1 DNA, allowing IN- HIV-1 mutants to mount a robust, spreading infection in CEM-SS cells. It remains unclear whether transcriptional activation of the HIV-1 LTR occurs before or after the change in epigenetic marks on the viral DNA, and this is something we wish to address, including in primary T cells. We now report preliminary data, obtained in 293T cells, showing that the HSV-1 ICP0 protein can also rescue IN- HIV-1 gene expression, in this case by apparently directly regulating the epigenetic status of unintegrated HIV-1 DNA. We aim to extend this analysis to T cells to see if ICP0 is indeed rescuing IN- HIV-1 gene expression via a different mechanism than Tax. Finally, while the factors that recognize and silence IN- MLV have been identified by the Goff laboratory as the HUSH complex acting in concert with NP220, we show that these factors are not required to silence IN- HIV-1. A key goal of this application is therefore to perform an unbiased CRISPR/Cas genetic screen to identify the human innate immune factors that perform this task and then define their mechanism of action.