PRC1-independent binding and activity of RYBP on the KSHV genome during de novo infection.
PRC1-independent binding and activity of RYBP on the KSHV genome during de novo infection.
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DOI：
10.1371/journal.ppat.1010801
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发表时间：
2022-08
期刊：
影响因子：
6.7
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中科院分区：
文献类型：
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卡波西肉瘤相关疱疹病毒 (KSHV) 是一种致癌病毒，在初次感染后建立潜伏期，导致人类终身感染。潜伏感染是持续感染和 KSHV 相关癌症发生的先决条件。虽然病毒裂解基因在初次感染后短暂表达，但其表达受到显着限制，并且伴随着宿主表观遗传阻遏物 Polycomb Repressive Complex 1 和 2（PRC1 和 PRC2）与裂解基因的结合。 PRC1 和 PRC2 分别介导抑制性组蛋白标记 H2AK119ub 和 H3K27me3，并维持 KSHV 裂解基因上的异染色质结构以抑制其表达。与 PRC2 相比，对于从头感染后 PRC1 因子在 KSHV 基因组上的招募和作用知之甚少。因此，本研究的目的是检查 PRC1 因子在建立 KSHV 潜伏期中的功能。为了解决这个问题，我们针对原发性 KSHV 感染期间典型和非典型 PRC1 复合物的 7 种不同成分进行了 shRNA 筛选。我们发现 RYBP 是非经典 PRC1 复合物的一个主要亚基，是 KSHV 裂解基因的有效抑制因子，它可以与病毒基因组结合，最早在感染后 4 小时就抑制裂解基因。令人惊讶的是，我们的 ChIP 分析表明 RYBP 以不依赖 PRC1 的方式与裂解病毒基因启动子结合，不影响 KSHV 基因组上的 PRC1 活性，并且可以降低与转录延伸相关的组蛋白标记水平。我们的数据还表明，RYBP 可以通过抑制裂解周期诱导剂 KSHV 基因 RTA 的转录延长来抑制初次感染后的病毒裂解周期。根据我们的结果，我们建议 RYBP 使用 PRC1 独立机制来阻断 KSHV RTA 表达，从而促进从头感染后 KSHV 潜伏期的建立。研究表明，细胞表观遗传因子通过控制初次感染后病毒基因的表达，在调节 KSHV DNA 染色质结构中发挥重要作用。潜伏期裂解基因的抑制受到各种抑制性表观遗传机制的调节，包括 PRC1 和 PRC2 介导的染色质修饰。在这项研究中，我们发现 RYBP（许多 PRC1 复合物的主要成分）是原发性 KSHV 感染期间 KSHV 裂解基因的新型抑制因子。先前的研究表明，RYBP 调节 PRC1 复合物的结合和酶活性，但令人惊讶的是，我们的数据表明 RYBP 对 KSHV 裂解基因的结合和抑制功能均不依赖于 PRC1。我们发现RYBP可以在从头感染过程中抑制裂解周期诱导病毒基因RTA的转录延伸，从而促进KSHV潜伏期的建立。总而言之，我们的研究揭示了 RYBP 在新病毒感染过程中 KSHV 基因沉默调节中的一种新颖的、非常规的作用。
Kaposi’s sarcoma-associated herpesvirus (KSHV) is an oncogenic virus that causes lifelong infection in humans by establishing latency after primary infection. Latent infection is a prerequisite for both persistent infection and the development of KSHV-associated cancers. While viral lytic genes are transiently expressed after primary infection, their expression is significantly restricted and concomitant with the binding of host epigenetic repressors Polycomb Repressive Complex 1 and 2 (PRC1 and PRC2) to lytic genes. PRC1 and PRC2 mediate the repressive histone marks H2AK119ub and H3K27me3, respectively, and maintain heterochromatin structure on KSHV lytic genes to inhibit their expression. In contrast to PRC2, little is known about the recruitment and role of PRC1 factors on the KSHV genome following de novo infection. Thus, the goal of this study was to examine the function of PRC1 factors in the establishment of KSHV latency. To address this question, we performed an shRNA screen targeting 7 different components of the canonical and non-canonical PRC1 complexes during primary KSHV infection. We found that RYBP, a main subunit of the non-canonical PRC1 complexes, is a potent repressor of KSHV lytic genes that can bind to the viral genome and inhibit lytic genes as early as 4 hours post infection. Surprisingly, our ChIP analyses showed that RYBP binds to lytic viral gene promoters in a PRC1-independent manner, does not affect PRC1 activity on the KSHV genome, and can reduce the level of histone marks associated with transcription elongation. Our data also suggest that RYBP can repress the viral lytic cycle after primary infection by inhibiting the transcription elongation of the lytic cycle inducer KSHV gene RTA. Based on our results we propose that RYBP uses a PRC1-independent mechanism to block KSHV RTA expression thereby promoting the establishment of KSHV latency following de novo infection. It has been shown that cellular epigenetic factors play an important role in regulating the chromatin structure of KSHV DNA by controlling the expression of viral genes following primary infection. The repression of lytic genes during latency is modulated by various inhibitory epigenetic mechanisms, including PRC1- and PRC2-mediated chromatin modifications. In this study, we identified RYBP, a major component of many PRC1 complexes, as a novel repressor of KSHV lytic genes during primary KSHV infection. Previous studies have shown that RYBP regulates the binding and enzymatic activity of PRC1 complexes, yet surprisingly, our data indicates that both the binding and repressive function of RYBP on KSHV lytic genes are PRC1-independent. We found that RYBP can inhibit the transcription elongation of the lytic cycle inducer viral gene RTA during de novo infection, thereby promoting the establishment of KSHV latency. Altogether, our study revealed a novel, non-canonical role of RYBP in the regulation of KSHV gene silencing during de novo viral infection.
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