Key result
Full-length NS3 and truncated NS3 with an RNA helicase domain enhanced IRES-mediated and cellular translation in a dose-dependent manner, an effect significantly enhanced by NS5B.
The classical swine fever virus RNA helicase NS3 promotes viral and cellular translation, an effect that is further enhanced by interaction with the viral replicase NS5B.
Hypothesis-generating for CSFV translation; leaves open NS3-NS5B as antiviral target in swine.
A full-length NS3 (NS3F) and a truncated NS3 protein (NS3H) with an RNA helicase domain possess RNA helicase activity. Using an in vitro system with a monocistronic reporter RNA or DNA, containing the CSFV 5'-UTR, we observed that both NS3F and NS3H enhanced internal ribosome entry site (IRES)-mediated and cellular translation in a dose-dependent manner, but NS3 protease (NS3P) that lacks a helicase domain did not. NS3F was stronger than NS3H in promoting both translations. These results showed that viral RNA helicase could promote viral and cellular translation, and higher RNA helicase activity might be more efficient. The NS5B protein, the viral replicase, did not significantly affect the IRES-directed or cellular translation alone. NS5B significantly enhanced the stimulative effect of NS3F on both IRES-mediated and cellular translation, but did not affect that of NS3H or NS3P. This suggests that NS5B and NS3 interact via the protease domain during the enhancement of translation.
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Xiao et al. (2008) studied Classical swine fever virus infection. NS3 and NS5B proteins vs. NS3 protease (NS3P) or alone was evaluated on Internal ribosome entry site (IRES)-mediated and cellular translation. Full-length NS3 and truncated NS3 with an RNA helicase domain enhanced IRES-mediated and cellular translation in a dose-dependent manner, an effect significantly enhanced by NS5B.
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