Sloan Elizabeth, Orr Anne, Everett Roger D
MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom.
J Virol. 2016 Sep 12;90(19):8621-33. doi: 10.1128/JVI.00621-16. Print 2016 Oct 1.
We previously reported that MORC3, a protein associated with promyelocytic leukemia nuclear bodies (PML NBs), is a target of herpes simplex virus 1 (HSV-1) ICP0-mediated degradation (E. Sloan, et al., PLoS Pathog 11:e1005059, 2015, http://dx.doi.org/10.1371/journal.ppat.1005059). Since it is well known that certain other components of the PML NB complex play an important role during an intrinsic immune response to HSV-1 and are also degraded or inactivated by ICP0, here we further investigate the role of MORC3 during HSV-1 infection. We demonstrate that MORC3 has antiviral activity during HSV-1 infection and that this antiviral role is counteracted by ICP0. In addition, MORC3's antiviral role extends to wild-type (wt) human cytomegalovirus (HCMV) infection, as its plaque-forming efficiency increased in MORC3-depleted cells. We found that MORC3 is recruited to sites associated with HSV-1 genomes after their entry into the nucleus of an infected cell, and in wt infections this is followed by its association with ICP0 foci prior to its degradation. The RING finger domain of ICP0 was required for degradation of MORC3, and we confirmed that no other HSV-1 protein is required for the loss of MORC3. We also found that MORC3 is required for fully efficient recruitment of PML, Sp100, hDaxx, and γH2AX to sites associated with HSV-1 genomes entering the host cell nucleus. This study further unravels the intricate ways in which HSV-1 has evolved to counteract the host immune response and reveals a novel function for MORC3 during the host intrinsic immune response.
Herpesviruses have devised ways to manipulate the host intrinsic immune response to promote their own survival and persistence within the human population. One way in which this is achieved is through degradation or functional inactivation of PML NB proteins, which are recruited to viral genomes in order to repress viral transcription. Because MORC3 associates with PML NBs in uninfected cells and is a target for HSV-1-mediated degradation, we investigated the role of MORC3 during HSV-1 infection. We found that MORC3 is also recruited to viral HSV-1 genomes, and importantly it contributes to the fully efficient recruitment of PML, hDaxx, Sp100, and γH2AX to these sites. Depletion of MORC3 resulted in an increase in ICP0-null HSV-1 and wt HCMV replication and plaque formation; therefore, this study reveals that MORC3 is an antiviral factor which plays an important role during HSV-1 and HCMV infection.
我们之前报道过，MORC3是一种与早幼粒细胞白血病核体（PML NBs）相关的蛋白质，是单纯疱疹病毒1型（HSV-1）ICP0介导的降解靶点（E. Sloan等人，《公共科学图书馆·病原体》11：e1005059，2015年，http://dx.doi.org/10.1371/journal.ppat.1005059）。由于众所周知，PML NB复合物的某些其他成分在对HSV-1的固有免疫反应中起重要作用，并且也被ICP0降解或失活，因此我们在此进一步研究MORC3在HSV-1感染过程中的作用。我们证明MORC3在HSV-1感染期间具有抗病毒活性，并且这种抗病毒作用被ICP0抵消。此外，MORC3的抗病毒作用扩展到野生型（wt）人巨细胞病毒（HCMV）感染，因为在MORC3缺失的细胞中其噬斑形成效率增加。我们发现，HSV-1基因组进入感染细胞的细胞核后，MORC3被募集到与HSV-1基因组相关的位点，在野生型感染中，在其降解之前，它随后与ICP0病灶相关联。MORC3的降解需要ICP0的RING指结构域，并且我们证实MORC3的缺失不需要其他HSV-1蛋白。我们还发现，MORC3是PML、Sp100、hDaxx和γH2AX充分有效地募集到与进入宿主细胞核的HSV-1基因组相关位点所必需的。这项研究进一步揭示了HSV-1为对抗宿主免疫反应而进化出的复杂方式，并揭示了MORC3在宿主固有免疫反应中的新功能。
疱疹病毒已经设计出操纵宿主固有免疫反应的方法，以促进它们在人群中的生存和持续存在。实现这一点的一种方式是通过降解PML NB蛋白或使其功能失活，这些蛋白被募集到病毒基因组以抑制病毒转录。由于MORC3在未感染细胞中与PML NBs相关联并且是HSV-1介导的降解靶点，我们研究了MORC3在HSV-1感染过程中的作用。我们发现MORC3也被募集到病毒HSV-1基因组，重要的是它有助于PML、hDaxx、Sp100和γH2AX充分有效地募集到这些位点。MORC3的缺失导致ICP0缺失的HSV-1和野生型HCMV复制及噬斑形成增加；因此，这项研究表明MORC3是一种抗病毒因子，在HSV-1和HCMV感染期间起重要作用。
