REGULATION OF GLYCOPROTEIN-D SYNTHESIS OF HERPES-SIMPLEX VIRUS-1 BY ALPHA-4 PROTEIN, THE MAJOR REGULATORY PROTEIN OF THE VIRUS, IN STABLY TRANSFORMED-CELL LINES - EFFECT OF THE RELATIVE GENE COPY NUMBERS

Earlier studies concerning gamma1 gene regulation by the alpha4 protei n, the major regulatory protein of herpes simplex virus 1 (HSV-1), in stably transformed cell lines, reported conflicting results, i.e., alp ha4 protein positively regulated the gamma1 gB gene in alpha4/gB cells , while it negatively regulated the gamma1 gD gene in alpha4/BJ cells. Both cell lines were derived from a common parental cell line alpha4/ c113 that contains 1 copy of the alpha4 gene, and the only apparent di fference between them was the relative copy number of the gB and gD se quences (1 and 30-50, respectively) resident in the cell genome. We in vestigated this disparity by constructing a cell line (BA4) that conta ins one copy each of the alpha4 and gamma1 gD sequences, by fusion of alpha4/c113 and BJt cells, containing and expressing respectively 1 co py of the alpha4 and gD genes. BA4 cells constitutively expressed both the alpha4, gD genes inherited from the parental cell lines (alpha4/c 113 and BJt). In BA4 cells the alpha4 protein positively regulates the gD gene as evidenced from (i) higher levels of gD expression than the parental BJt cells lacking the alpha4 gene, and (ii) significant decr ease in gD expression under conditions that render the alpha4 protein produced in BA 4 cells non-functional. In addition the gamma2gG gene c ontained within the DNA fragment encoding the gD gene, is also express ed in BA 4 cells. On the basis of these data, we propose that gamma ge ne regulation by the alpha4 protein is affected by the relative copy n umber of these genes, resident in the cell genome.