González-Mariscal J A, Fernández-Trujillo M A, Alonso M C, García-Rosado E, Álvarez M C, Béjar J
Universidad de Málaga, Department of Genetics, Spain.
Universidad de Málaga, Department of Microbiology, Spain.
Vet Immunol Immunopathol. 2016 Mar;171:73-80. doi: 10.1016/j.vetimm.2016.02.006. Epub 2016 Feb 16.
The understanding of virus-host interactions relies on the knowledge of the regulatory mechanisms of the type I interferon (IFN I)-stimulated genes (ISGs). Among ISGs, those coding Mx proteins play a main role due to their direct antiviral activity. The study of these genes in gilthead seabream is interesting, since this species displays high natural resistance to viral diseases, being asymptomatic carrier of infectious pancreatic necrosis virus (IPNV) and viral haemorrhagic septicaemia virus (VHSV). Gilthead seabream has three Mx genes (Mx1, Mx2, and Mx3), encoding proteins with a wide spectrum of antiviral activity. The structure of the three promoters (pMx1, pMx2 and pMx3) has been previously disclosed, and their response to poly I:C in RTG-2 cells characterized. To further analyze these promoters, their response to two viral infections has been evaluated in the present study. For that purpose, RTG-2 cells transiently transfected with the luciferase gene under the control of each promoter were inoculated with either IPNV or VHSV at two different doses. The highest and lowest fold induction values were recorded for pMx2 and pMx3, respectively. The promoter induction was always stronger after VHSV inoculation than in IPNV-inoculated cells. In addition, the higher dose of VHSV tested induced higher response of the three promoters, whereas in IPNV-infected cells the highest induction was recorded after inoculation with the lower viral dose. To further study the response of the Mx2 promoter, RTG-2 cells stably transfected with the luciferase gene under the control of pMx2 were stimulated with poly I:C and subsequently infected with IPNV or VHSV. Interestingly, IPNV infection inhibited the induction caused by poly I:C, suggesting an antagonistic activity of IPNV on Mx2 transcription. In contrast, VHSV infection did not alter the response triggered by poly I:C. These results highlight the specific regulation that controls the activity of each promoter, and support the existence of complex interactions between host cells, specific Mx promoters, and viruses, which are responsible for the final outcome of a viral infection.
对病毒 - 宿主相互作用的理解依赖于对I型干扰素（IFN I）刺激基因（ISG）调控机制的了解。在ISG中，那些编码Mx蛋白的基因因其直接的抗病毒活性而发挥主要作用。对金头鲷中这些基因的研究很有趣，因为该物种对病毒疾病表现出高度的天然抗性，是传染性胰腺坏死病毒（IPNV）和病毒性出血性败血症病毒（VHSV）的无症状携带者。金头鲷有三个Mx基因（Mx1、Mx2和Mx3），编码具有广泛抗病毒活性的蛋白质。先前已经揭示了三个启动子（pMx1、pMx2和pMx3）的结构，并对它们在RTG - 2细胞中对聚肌胞苷酸（poly I:C）的反应进行了表征。为了进一步分析这些启动子，在本研究中评估了它们对两种病毒感染的反应。为此，用每种启动子控制下的荧光素酶基因瞬时转染的RTG - 2细胞，以两种不同剂量接种IPNV或VHSV。pMx2和pMx3分别记录到最高和最低的诱导倍数。接种VHSV后启动子的诱导总是比接种IPNV的细胞更强。此外，测试的较高剂量的VHSV诱导了三个启动子更高的反应，而在IPNV感染的细胞中，接种较低病毒剂量后记录到最高诱导。为了进一步研究Mx2启动子的反应，用pMx2控制下的荧光素酶基因稳定转染的RTG - 2细胞用聚肌胞苷酸（poly I:C）刺激，随后感染IPNV或VHSV。有趣的是，IPNV感染抑制了聚肌胞苷酸（poly I:C）引起的诱导，表明IPNV对Mx2转录具有拮抗活性。相反，VHSV感染没有改变聚肌胞苷酸（poly I:C）触发的反应。这些结果突出了控制每个启动子活性的特定调控，并支持宿主细胞、特定的Mx启动子和病毒之间存在复杂的相互作用，这些相互作用决定了病毒感染的最终结果。
