Alteration of the subcellular localization of hepatitis B virus core protein by large but not small surface proteins

By performing immunofluorescence staining assays in confluent COS-7 cells, hepatitis B virus core, small surface and large surface proteins were found to localize largely in the nucleus, diffusely in the cytoplasm, and accumulatively in a perinuclear area, respectively. When two proteins were co-expressed, the core protein was found co-localized with the large but not small surface protein in the cytoplasm. By performing subcellular fractionation experiments, the large surface protein was found to reduce the amount of the core protein in the nuclear fraction to an undetectable level. These results indicate that the large but not small surface protein can alter the subcellular localization of the core protein.