Regulation of secretion of the hepatitis B virus major surface antigen by the preS-1 protein.

P24, P30, and P39, the three major surface antigens of the envelope of hepatitis B virus, are co-carboxy-terminal proteins with different amino-terminal extensions. We prompted expression of these proteins in Chinese hamster ovary (CHO) cells by placing the appropriate coding sequence(s) under the control of the simian virus 40 early promoter. P24 and P30 formed 22-nm particles which were efficiently secreted. In contrast, P39 accumulated in a perinuclear structure, presumably the Golgi complex, and was not secreted. Coexpressing P39 and P24 resulted in the localization of both in the perinuclear region and restricted the secretion of P24. We found that P39 must be expressed at a relatively low level to allow efficient secretion of P24 in typical spherical particles. We hypothesize that P39, by inhibiting the formation of spherical particles, helps to induce formation of filamentous particles and mature Hepatitis B virus.