Protein arginine methyltransferases (PRMT6) has been shown to negatively regulate interferon (IFN) production in mammals, however, the role of teleost PRMT6 in IFN signaling remains largely unknown. In our previous study, black carp (Mylopharyngodon piceus) PRMT6 (bcPRMT6) has been identified to inhibit bcTBK1/bcIRF3 cascade. In this study, bcIRF3-induced transcription of bcIFNa, bcIFNb, bcp50 and bcIl1β in host cells was attenuated by co-expressed bcPRMT6. Accordingly, bcIRF3-mediated antiviral activity against grass carp reovirus (GCRV) and spring viremia of carp virus (SVCV) was obviously dampened by bcPRMT6. Knockdown of bcPRMT6 enhanced the antiviral ability of host cells and improved the transcription of bcIFNa, bcViperin and bcIl1β. When co-expressed with bcPRMT6 in either mammalian or fish cells, the protein level of bcIRF3 was decreased, which implied the triggered degradation of bcIRF3 by bcPRMT6. And interestingly, this decreased protein expression of bcIRF3 was rescued by chloroquine but not MG132, indicating the lysosome-dependent degradation of this molecule. The subsequent immunoprecipitation and immunoblot assay demonstrated that K63-linked ubiquitination but not K48-linked of bcIRF3 was obviously attenuated by bcPRMT6. And the immunofluorescent staining data suggested that the nuclear translocation of bcIRF3 was inhibited by bcPRMT6. Taken together, our data concludes that bcPRMT6 promotes the degradation of bcIRF3 through lysosome pathway and inhibits K63-linked ubiquitination of bcIRF3, leading to the dampened antiviral signaling mediated by bcIRF3.

蛋白质精氨酸甲基转移酶 (PRMT6) 已被证明对哺乳动物的干扰素 (IFN) 产生负调节作用，然而，硬骨鱼 PRMT6 在 IFN 信号传导中的作用仍然很大程度上未知。在我们之前的研究中，已确定黑鲤 ( Mylopharyngodon piceus ) PRMT6 (bcPRMT6) 可抑制 bcTBK1/bcIRF3 级联反应。在本研究中，共表达的 bcPRMT6 减弱了 bcIRF3 诱导的宿主细胞中bcIFNa、bcIFNb、bcp50 和 bcIl1β的转录。因此，bcPRMT6 明显抑制了 bcIRF3 介导的对草鱼呼肠孤病毒 (GCRV) 和鲤春病毒血症 (SVCV) 的抗病毒活性。bcPRMT6 的敲低增强了宿主细胞的抗病毒能力并改善了bcIFNa、bcViperin 和 bcIl1β的转录. 当在哺乳动物或鱼类细胞中与 bcPRMT6 共表达时，bcIRF3 的蛋白质水平降低，这意味着 bcPRMT6 触发了 bcIRF3 的降解。有趣的是，这种降低的 bcIRF3 蛋白表达被氯喹而不是 MG132 拯救，表明该分子的溶酶体依赖性降解。随后的免疫沉淀和免疫印迹分析表明，bcPRMT6 明显减弱了 BcIRF3 的 K63 连接的泛素化而非 K48 连接的泛素化。并且免疫荧光染色数据表明bcIRF3的核转位受到bcPRMT6的抑制。总之，我们的数据得出结论，bcPRMT6 通过溶酶体途径促进 bcIRF3 的降解并抑制 BcIRF3 的 K63 泛素化，导致 bcIRF3 介导的抗病毒信号传导减弱。