Qingdao Key Laboratory of Mariculture Epidemiology and Biosecurity, Key Laboratory of Maricultural Organism Disease Control, Ministry of Agriculture, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China.
Function Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China.
Cells. 2022 Mar 13;11(6):982. doi: 10.3390/cells11060982.
Elemental iron is an indispensable prosthetic group of DNA replication relative enzymes. The upregulation of ferritin translation by iron regulatory proteins (IRP1) in host cells is a nutritional immune strategy to sequester available iron to pathogens. The efficient replication of Ostreid herpesvirus 1 (OsHV-1), a lethal dsDNA virus among bivalves, depends on available iron. OsHV-1 infection was found to trigger iron limitation in ark clams; however, it is still an enigma how OsHV-1 successfully conducted rapid replication, escaping host iron limitations. In this study, we identified the IRP1 protein (designated as SbIRP-1) in the ark clam (Scapharca broughtonii) and found it could bind to the iron-responsive element (IRE) of ferritin (SbFn) mRNA based on electrophoretic mobility shift assay (EMSA). Knockdown of SbIRP-1 expression (0.24 ± 1.82-fold of that in NC group, p < 0.01) by RNA interference resulted in the accumulation of SbFn in hemocytes (1.79 ± 0.01-fold, p < 0.01) post-24 h of enhanced RNA interference injection. During OsHV-1 infection, SbFn mRNA was significantly upregulated in hemocytes from 24 h to 60 h, while its protein level was significantly reduced from 24 h to 48 h, with the lowest value at 36 h post-infection (0.11 ± 0.01-fold, p < 0.01). Further analysis by RNA immunoprecipitation assays showed that OsHV-1 could enhance the binding of SbIRP-1 with the SbFn IRE, which was significantly increased (2.17 ± 0.25-fold, p < 0.01) at 36 h post-infection. Consistently, SbIRP-1 protein expression was significantly increased in hemocytes from 12 h to 48 h post OsHV-1 infection (p < 0.01). In conclusion, the results suggest that OsHV-1 infection could suppress post-transcriptional translation of SbFn through the regulation of SbIRP-1, which likely contributes to OsHV-1 evasion of SbFn-mediating host iron limitation.
元素铁是 DNA 复制相关酶必不可少的辅基。铁调节蛋白（IRP1）在宿主细胞中上调铁蛋白的翻译，是将可用铁隔离给病原体的营养免疫策略。牡蛎疱疹病毒 1（OsHV-1）是一种致命的双 DNA 病毒，在双壳类动物中，其有效的复制依赖于可用铁。研究发现，OsHV-1 感染会引发蛤仔铁限制；然而，OsHV-1 如何成功地进行快速复制，逃避宿主铁限制仍然是一个谜。在这项研究中，我们在蛤仔（Scapharca broughtonii）中鉴定了 IRP1 蛋白（命名为 SbIRP-1），并发现它可以根据电泳迁移率变动分析（EMSA）与铁反应元件（IRE）结合铁蛋白（SbFn）mRNA。RNA 干扰导致 SbIRP-1 表达下调（NC 组的 0.24 ± 1.82 倍，p < 0.01），24 小时后，血淋巴细胞中 SbFn 积累（1.79 ± 0.01 倍，p < 0.01）。在 OsHV-1 感染期间，血淋巴细胞中的 SbFn mRNA 从 24 小时到 60 小时显著上调，而其蛋白水平从 24 小时到 48 小时显著降低，感染后 36 小时达到最低值（0.11 ± 0.01 倍，p < 0.01）。RNA 免疫沉淀分析进一步表明，OsHV-1 可以增强 SbIRP-1 与 SbFn IRE 的结合，在感染后 36 小时明显增加（2.17 ± 0.25 倍，p < 0.01）。同样，感染 OsHV-1 后 12 小时到 48 小时，血淋巴细胞中的 SbIRP-1 蛋白表达显著增加（p < 0.01）。综上所述，结果表明，OsHV-1 感染可能通过调节 SbIRP-1 来抑制 SbFn 的转录后翻译，这可能有助于 OsHV-1 逃避 SbFn 介导的宿主铁限制。
