Mechanical regulation of the helicase activity of Zika virus NS3

  • Xiaocong Cao
    Department of Obstetrics and Gynecology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
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  • Kaixian Liu
    Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York
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  • Shannon Yan
    Institute of Quantitative Biosciences (QB3), University of California-Berkeley, Berkeley, California
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  • Sai Li
    Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, New York
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  • Yajuan Li
    Department of Clinical Laboratory, The First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China
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  • Tengchuan Jin
    Corresponding author
    Department of Obstetrics and Gynecology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China

    Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China

    CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Science, Shanghai, China
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  • Shixin Liu
    Corresponding author
    Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, New York
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Published:August 02, 2022DOI:


      Zika virus (ZIKV) is a positive-sense single-stranded RNA virus that infects humans and can cause birth defects and neurological disorders. Its non-structural protein 3 (NS3) contains a protease domain and a helicase domain, both of which play essential roles during the viral life cycle. However, it has been shown that ZIKV NS3 has an inherently weak helicase activity, making it unable to unwind long RNA duplexes alone. How this activity is stimulated to process the viral genome and whether the two domains of NS3 are functionally coupled remain unclear. Here, we used optical tweezers to characterize the RNA-unwinding properties of ZIKV NS3—including its processivity, velocity, and step size—at the single-molecule level. We found that external forces that weaken the stability of the duplex RNA substrate significantly enhance the helicase activity of ZIKV NS3. On the other hand, we showed that the protease domain increases the binding affinity of NS3 to RNA but has only a minor effect on unwinding per se. Our findings suggest that the ZIKV NS3 helicase is activated on demand in the context of viral replication, a paradigm that may be generalizable to other flaviviruses.
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