A Recombinant Zika Virus RNA-Dependent RNA Polymerase Capable of Copying Viral RNA Templates
Hae-Gwang Jung, Seung-Hoon Lee, Ji-Eun Lee, and Jong-Won Oh* Department of Biotechnology, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
Zika virus (ZIKV), a mosquito-borne arbovirus in the genus Flavivirus, has emerged as a global health security threat because ZIKV infection can cause not only microcephaly in infants but also various neurological disorders including Guillain-Barré syndrome, meningoencephalitis, and myelitis in adults. Despite these severe disease outcomes, currently, neither vaccines nor specific antiviral drugs are available to prevent or treat ZIKV infections. Therefore, development of countermeasures to control ZIKV is urgently needed. Similar to other flaviviruses, ZIKV replicates its plus-strand RNA viral genome by a virally encoded RNA-dependent RNA polymerase (RdRp). Thus, this RdRp domain in the C-terminal part of the nonstructural (NS) protein 5 is an attractive target for direct-acting antiviral agents (DAAs). In the present study, we cloned and expressed a full-length recombinant ZIKA NS5 to establish an in vitro RdRp assay system using the purified NS5 protein capable of copying viral RNA templates. The purified NS5 containing the N-terminal domain with the methyltransferase activity and the C-terminal domain with the RdRp activity showed primer-dependent RNA synthesis activity on a homopolymeric RNA template. It was also able to initiate de novo RNA synthesis from the 3′-ends of both the plus- and minus-strand RNA of ZIKV. The RdRp activity was found to be enhanced by the N-terminal domain of NS5. The in vitro RdRp assay system established with a full-length NS5 will be useful for understanding the mechanisms of ZIKV RNA genome replication and for the development of anti-ZIKV DAAs.
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