CNRS FRE3235, Université Paris Descartes, 45 rue des Saints Pères, 75006 Paris, France.
J Virol. 2011 Dec;85(24):13164-73. doi: 10.1128/JVI.05808-11. Epub 2011 Oct 12.
Promyelocytic leukemia (PML) protein is the organizer of nuclear matrix-associated nuclear bodies (NBs), and its conjugation to the small ubiquitin-like modifier (SUMO) is required for the formation of these structures. Several alternatively spliced PML transcripts from a single PML gene lead to the production of seven PML isoforms (PML isoform I [PMLI] to VII [PMLVII]), which all share a N-terminal region that includes the RBCC (RING, B boxes, and a α-helical coiled-coil) motif but differ in the C-terminal region. This diversity of PML isoforms determines the specific functions of each isoform. There is increasing evidence implicating PML in host antiviral defense and suggesting various strategies involving PML to counteract viral production. We reported that mouse embryonic fibroblasts derived from PML knockout mice are more sensitive than wild-type cells to infection with encephalomyocarditis virus (EMCV). Here, we show that stable expression of PMLIV or PMLIVa inhibited viral replication and protein synthesis, leading to a substantial reduction of EMCV multiplication. This protective effect required PMLIV SUMOylation and was not observed with other nuclear PML isoforms (I, II, III, V, and VI) or with the cytoplasmic PMLVII. We demonstrated that only PMLIV interacted with EMCV 3D polymerase (3Dpol) and sequestered it within PML NBs. The C-terminal region specific to PMLIV was required for both interaction with 3Dpol and the antiviral properties. Also, depletion of PMLIV by RNA interference significantly boosted EMCV production in interferon-treated cells. These findings indicate the mechanism by which PML confers resistance to EMCV. They also reveal a new pathway mediating the antiviral activity of interferon against EMCV.
早幼粒细胞白血病（PML）蛋白是核基质相关核体（NBs）的组织者，其与小泛素样修饰物（SUMO）的缀合对于这些结构的形成是必需的。单个 PML 基因的几个选择性剪接的 PML 转录本导致产生七个 PML 同工型（PML 同工型 I [PMLI]至 VII [PMLVII]），它们都共享一个包含 RBCC（RING、B 盒和一个 α-螺旋卷曲螺旋）基序的 N 端区域，但在 C 端区域不同。PML 同工型的这种多样性决定了每个同工型的特定功能。越来越多的证据表明 PML 参与宿主抗病毒防御，并提出了各种涉及 PML 的策略来对抗病毒产生。我们报道了来自 PML 敲除小鼠的胚胎成纤维细胞比野生型细胞对脑炎心肌炎病毒（EMCV）的感染更敏感。在这里，我们表明 PMLIV 或 PMLIVa 的稳定表达抑制了病毒复制和蛋白质合成，导致 EMCV 增殖的大量减少。这种保护作用需要 PMLIV SUMOylation，并且不会观察到其他核 PML 同工型（I、II、III、V 和 VI）或细胞质 PMLVII。我们证明只有 PMLIV 与 EMCV 3D 聚合酶（3Dpol）相互作用，并将其隔离在 PML NBs 内。PMLIV 特有的 C 端区域对于与 3Dpol 的相互作用和抗病毒特性都是必需的。此外，通过 RNA 干扰耗尽 PMLIV 可显著促进干扰素处理细胞中 EMCV 的产生。这些发现表明了 PML 赋予对 EMCV 抗性的机制。它们还揭示了一种介导干扰素对 EMCV 抗病毒活性的新途径。
