CONCOMITANT CELLULAR EXPRESSION OF HEAT-SHOCK REGULATED GENES OF HEPATITIS-B VIRUS SURFACE-ANTIGEN AND OF HUMAN GROWTH-HORMONE BY A NIH-3T3CELL-LINE

A plasmid carrying a DNA fragment of hepatitis B virus, coding for the pre-S2 and the entire S region of the surface antigen (HBsAg), placed under the control of the promoter of the human 70 kDa heat shock prot ein gene (hsp70), was introduced into Line 6, a recombinant cell line that was selected from NIH-3T3 cells previously transfected with a sim ilar construct coding for the human growth hormone cDNA gene (chGH) an d with the plasmid pEJ carrying the Ha-ras(EJ) activated cellular onco gene The resulting cell line, EMS8, expressed: (1) hsp70/HBsAg and hsp 70/hGH hybrid genes, (2) the human Ha-ras(EJ) oncogene, and (3) the ne omycin resistance gene, the two last plasmid markers being used for ce ll selection. EMS8 cells were able to carry out post-translational mod ifications of the middle M and the major S envelope proteins of HBV, s uch as assembly and glycosylation. Accordingly, the cells synthesized and secreted both fi ee and glycosylated M and S viral proteins, and t he human growth hormone protein. In addition concomitant expression of HBsAg and hGH proteins as well as their mRNA were detected in EMS8 ce lls at least lip to 72 hr after heat induction instead of 24 hr in the case of hGH in Line 6 cells.