| Abstract |
To study the role of mutant precore region in expression and secretion of hapatitis B viral core antigen, we have cloned core antigen gene(HBc) with or without precore region in geterologous expression vectors containing SV40 promoter, yeast promoter, and lambda P_L promoter. In COS cells transfected with plasmid containing C-gene with precore region, antigens were detected in both cell extract and cultured medium. However, in the cells transfected with plasmids containing C-gene without precore or with mutated precore region by one nucleotide (T) addition at the nucleotide 1,821, HBcAg was detected only in cell extracts. These results support that the mutation by one nucleotide addition shifted the initiation codon of precore region to 53 nucleotides upward and the elongated precore region also played a major role in the secretion of HBcAg in mammalian cells. In the case of yeast and E. coli, HBcAg was detected only in cell extracts in spite of the presence of precore region, which suggest that precore region could not affect HBcAg secretion in these system. |
