Singh Pankaj, Neumann Donna M
Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA
J Virol. 2021 May 10;95(11). doi: 10.1128/JVI.00364-21. Epub 2021 Mar 10.
Herpes Simplex Virus 1 (HSV-1) is a human pathogen that has the ability to establish a lifelong infection in the host. During latency, HSV-1 genomes are chromatinized and are abundantly associated with histones in sensory neurons, yet the mechanisms that govern the latent-lytic transition remain unclear. We hypothesize that the latent-lytic switch is controlled by CTCF insulators, positioned within the HSV-1 latent genome. CTCF insulators, together with the cohesin complex, have the ability to establish and maintain chromtin loops that allow distance separated gene regions to be spatially oriented for transcriptional control. In this current study, we demonstrated that the cohesin subunit Rad21 was recruited to latent HSV-1 genomes near four of the CTCF insulators during latency. We showed that the CTCF insulator known as CTRS1/2, positioned downstream from the essential transactivating IE region of ICP4 was only enriched in Rad21 prior to but not during latency, suggesting that the CTRS1/2 insulator is not required for the maintenance of latency. Further, deletion of the CTRL2 insulator, positioned downstream from the LAT enhancer, resulted in a loss of Rad21 enrichment at insulators flanking the ICP4 region at early times post-infection in mice ganglia, suggesting that these insulators are interdependent. Finally, deletion of the CTRL2 insulator resulted in a loss of Rad21 enrichment at the CTRL2 insulator in a cell-type specific manner, and this loss of Rad21 enrichment was correlated to decreased LAT expression, suggesting that Rad21 recruitment to viral genomes is important for efficient gene expression.CTCF insulators are important for transcriptional control and increasing evidence suggests that that CTCF insulators, together with the cohesin complex, regulate viral transcription in DNA viruses. The CTCF-cohesin interaction is important for the formation of chromatin loops, structures that orient distance separated elements in close spatial proximity for transcriptional control. Herpes Simplex Virus 1 (HSV-1) has seven putative CTCF insulators that flank the LAT and the IE, indicating that CTCF insulators play a role in the transition from latency to reactivation. Contributions from the work presented here include the finding that CTCF insulators in HSV-1 genomes are differentially enriched in the cohesin subunit Rad21, suggesting that CTCF-cohesin interactions could be establishing and anchoring chromatin loop structures to control viral transcription.
单纯疱疹病毒1型（HSV-1）是一种人类病原体，能够在宿主体内建立终身感染。在潜伏期，HSV-1基因组会发生染色质化，并在感觉神经元中与组蛋白大量结合，然而，控制潜伏-裂解转换的机制仍不清楚。我们假设潜伏-裂解开关由位于HSV-1潜伏基因组内的CTCF绝缘子控制。CTCF绝缘子与黏连蛋白复合体一起，有能力建立和维持染色质环，使距离较远的基因区域在空间上定向以进行转录控制。在本研究中，我们证明在潜伏期，黏连蛋白亚基Rad21被招募到四个CTCF绝缘子附近的潜伏HSV-1基因组中。我们发现，位于ICP4必需反式激活IE区域下游的名为CTRS1/2的CTCF绝缘子仅在潜伏期之前而非潜伏期期间在Rad21中富集，这表明CTRS1/2绝缘子对于维持潜伏期并非必需。此外，删除位于LAT增强子下游的CTRL2绝缘子，导致在小鼠神经节感染后早期，ICP4区域两侧绝缘子处的Rad21富集丧失，这表明这些绝缘子相互依赖。最后，删除CTRL2绝缘子导致Rad21在CTRL2绝缘子处的富集以细胞类型特异性方式丧失，而这种Rad21富集的丧失与LAT表达降低相关，这表明Rad21被招募到病毒基因组对于有效的基因表达很重要。CTCF绝缘子对于转录控制很重要，越来越多的证据表明，CTCF绝缘子与黏连蛋白复合体一起，在DNA病毒中调节病毒转录。CTCF-黏连蛋白相互作用对于染色质环的形成很重要，染色质环这种结构使距离较远的元件在空间上紧密靠近以进行转录控制。单纯疱疹病毒1型（HSV-1）在LAT和IE两侧有七个假定的CTCF绝缘子，这表明CTCF绝缘子在从潜伏期到再激活的转换中起作用。本研究的贡献包括发现HSV-1基因组中的CTCF绝缘子在黏连蛋白亚基Rad21中的富集存在差异，这表明CTCF-黏连蛋白相互作用可能正在建立和锚定染色质环结构以控制病毒转录。
