Nuclear localization of the NS3 protein of hepatitis C virus and factors affecting the localization

Subcellular localization of the NS2 and NS3 proteins of hepatitis C virus was analysed, In stable Ltk transfectants inducibly expressing an NS2-NS3 polyprotein (amino acids [aa] 810 to 1463), processed full-size NS2 (aa 810 to 1026) was detected exclusively in a cytoplasmic membrane fraction, On the other hand, the other processed product, carboxy-truncated NS3 (NS3 Delta C1463; aa 1027 to 1463), was present in both cytoplasmic and nuclear fractions, To further analyze subcellular localization of NS3, NS3 Delta C1459 (aa 1027 to 1459), full-size NS3 (NS3F; aa 1027 to 1657) and both amino- and carboxy-truncated NS3 (NS3 Delta N Delta C; aa 1201 to 1459) were expressed in HeLa cells by using a vaccinia virus-T7 hybrid expression system. NS3 Delta C1459 and NS3F accumulated in the nucleus as well as in the cytoplasm, exhibiting a dot-like staining pattern, On the other hand; NS3 Delta N Delta C was localized predominantly in the cytoplasm, suggesting the presence of a nuclear localization signal(s) in the amino-terminal sequence of NS3. NS4A, a viral cofactor for the NS3 protease, inhibited nuclear transport of NS3 Delta C1459 and NS3F, with the latter inhibited to a lesser extent than was the former. interestingly, wild-type p53 tumor suppressor augmented nuclear localization of NS3 Delta C1459 and NS3F, whereas mutant-type p53 inhibited nuclear localization and augmented cytoplasmic localization of NS3 Delta C1459. However, subcellular localization of NS3 Delta N Delta C was not affected by either type of p53, Wild-type p53-mediated nuclear accumulation of NS3 Delta C1459 and NS3F was inhibited partially, but not completely, by coexpressed NS4A, with NS3F again affected less prominently than was NS3 Delta C1459.