| Summary: | 碩士 === 國立陽明大學 === 醫學生物技術暨檢驗學系暨研究所 === 97 === Enterovirus 71 (EV71), a member of Picornaviridae family, can lead to severe neurological complications, and has caused several large outbreaks in Taiwan since 1998. The 5’ untranslated region (5’-UTR) of viruses is highly structured, containing the internal ribosomal entry site (IRES) that is critical for translation initiation. The efficiency of IRES-dependent translation is concerned with the infectivity of viruses, but whether the IRES is concerned with neurotropism or not is still controversial. On the other hand, the IRES-dependent translation initiation needs noncanonical factors called IRES trans-acting factors (ITAFs). Nowadays, the understanding of EV71 ITAFs is still limited.
In this study, we used a dual-luciferase reporter system that harbored IRES from EMCV, EV71 BrCr strain, EV71 B5 strain Taiwan isolate, Sabin type 3 vaccine strain, Sabin type 3 revertant strain, and CA16. By analyzing the IRES activities in neural and non-neural cells, we found that different viruses showed distinct IRES activities, yet each IRES activity is comparable in the two origins of cells. Accordingly, we suggested that the neurotropism of human enterovirus is not governed by viral IRES.
Additionally, we investigated La, PTB, PCBP2, and Unr, the known ITAFs of poliovirus, on their roles in interacting with EV71 IRES. Utilizing RNA interference strategy to knock down these proteins in HeLa cells, we showed that knock down of Unr, but not other ITAFs, could significantly decrease EV71 IRES activity. The decreased level of Unr also led to reduced viral protein expression and viral particle production. We revealed that Unr, among the ITAFs investigated, played the most significant role in controlling EV71 IRES.
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