Liu Baoming, Li Nan L, Wang Jie, Shi Pei-Yong, Wang Tianyi, Miller Mark A, Li Kui
Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, Memphis, Tennessee, USA.
Wadsworth Center, New York State Department of Health, Albany, New York, USA.
J Virol. 2014 Dec;88(23):13821-35. doi: 10.1128/JVI.02505-14. Epub 2014 Sep 24.
The tripartite motif-containing (TRIM) proteins have emerged as a new class of host antiviral restriction factors, with several demonstrating roles in regulating innate antiviral responses. Of >70 known TRIMs, TRIM56 inhibits replication of bovine viral diarrhea virus, a ruminant pestivirus of the family Flaviviridae, but has no appreciable effect on vesicular stomatitis virus (VSV), a rhabdovirus. Yet the antiviral spectrum of TRIM56 remains undefined. In particular, how TRIM56 impacts human-pathogenic viruses is unknown. Also unclear are the molecular determinants governing the antiviral activities of TRIM56. Herein, we show that TRIM56 poses a barrier to infections by yellow fever virus (YFV), dengue virus serotype 2 (DENV2), and human coronavirus virus (HCoV) OC43 but not encephalomyocarditis virus (EMCV). Moreover, by engineering cell lines conditionally expressing various TRIM56 mutants, we demonstrated that TRIM56's antiflavivirus effects required both the E3 ligase activity that lies in the N-terminal RING domain and the integrity of its C-terminal portion, while the restriction of HCoV-OC43 relied upon the TRIM56 E3 ligase activity alone. Furthermore, TRIM56 was revealed to impair YFV and DENV2 propagation by suppressing intracellular viral RNA accumulation but to compromise HCoV-OC43 infection at a later step in the viral life cycle, suggesting that distinct TRIM56 domains accommodate differing antiviral mechanisms. Altogether, TRIM56 is a versatile antiviral host factor that confers resistance to YFV, DENV2, and HCoV-OC43 through overlapping and distinct molecular determinants.
We previously reported tripartite motif protein 56 (TRIM56) as a host restriction factor of bovine viral diarrhea virus, a ruminant pathogen. However, the impact of TRIM56 on human-pathogenic RNA viruses is unknown. Herein, we demonstrate that TRIM56 restricts two medically important flaviviruses, yellow fever virus (YFV) and dengue virus serotype 2 (DENV2), and a human coronavirus, HCoV-OC43, but not encephalomyocarditis virus, a picornavirus. Further, we show that TRIM56-mediated inhibition of HCoV-OC43 multiplication depends solely on its E3 ligase activity, whereas its restriction of YFV and DENV2 requires both the E3 ligase activity and integrity of the C-terminal portion. The differing molecular determinants appear to accommodate distinct antiviral mechanisms TRIM56 adopts to target different families of viruses; while TRIM56 curbs intracellular YFV/DENV2 RNA replication, it acts at a later step in HCoV-OC43 life cycle. These novel findings illuminate the molecular basis of the versatility and specificity of TRIM56's antiviral activities against positive-strand RNA viruses.
含三联基序的（TRIM）蛋白已成为一类新的宿主抗病毒限制因子，其中几种在调节先天性抗病毒反应中发挥作用。在已知的70多种TRIM蛋白中，TRIM56可抑制牛病毒性腹泻病毒（一种黄病毒科的反刍动物瘟病毒）的复制，但对弹状病毒水泡性口炎病毒（VSV）没有明显影响。然而，TRIM56的抗病毒谱仍不明确。特别是，TRIM56如何影响人类致病病毒尚不清楚。TRIM56抗病毒活性的分子决定因素也不清楚。在此，我们表明TRIM56对黄热病毒（YFV）、登革病毒2型（DENV2）和人冠状病毒（HCoV）OC43的感染构成障碍，但对脑心肌炎病毒（EMCV）没有影响。此外，通过构建条件表达各种TRIM56突变体的细胞系，我们证明TRIM56的抗黄病毒作用既需要位于N端RING结构域的E3连接酶活性，也需要其C端部分的完整性，而对HCoV-OC43的限制仅依赖于TRIM56的E3连接酶活性。此外，研究发现TRIM56通过抑制细胞内病毒RNA积累来损害YFV和DENV2的增殖，但在病毒生命周期的后期损害HCoV-OC43的感染，这表明不同的TRIM56结构域适应不同的抗病毒机制。总之，TRIM56是一种多功能的抗病毒宿主因子，通过重叠和不同的分子决定因素赋予对YFV、DENV2和HCoV-OC43的抗性。
我们之前报道三联基序蛋白56（TRIM56）是反刍动物病原体牛病毒性腹泻病毒 的宿主限制因子。然而，TRIM56对人类致病RNA病毒的影响尚不清楚。在此，我们证明TRIM56可限制两种医学上重要的黄病毒，即黄热病毒（YFV）和登革病毒2型（DENV2），以及一种人冠状病毒HCoV-OC43，但对小RNA病毒脑心肌炎病毒没有影响。此外，我们表明TRIM56介导的对HCoV-OC43增殖的抑制仅取决于其E3连接酶活性，而其对YFV和DENV2的限制则需要E3连接酶活性和C端部分的完整性。不同的分子决定因素似乎适应TRIM56针对不同病毒家族采用的不同抗病毒机制；虽然TRIM56抑制细胞内YFV/DENV2 RNA复制，但它在HCoV-OC43生命周期的后期起作用。这些新发现阐明了TRIM56对正链RNA病毒抗病毒活性的多功能性和特异性的分子基础。
