TRANSCRIPTIONAL CONTROL OF HUMAN PAPILLOMAVIRUS TYPE-18 ONCOGENE EXPRESSION IN DIFFERENT CELL-LINES - ROLE OF TRANSCRIPTION FACTOR YY1

Binding of YY1 to the proximal fragment of the human papillomavirus ty pe 18 (HPV-18) upstream regulatory region (URR) activates the oncogene expression of HPV-18 in HeLa cells, whereas in HepG2 cells this expre ssion is repressed by YY1. In the present transient transfection study , we analyze the regulation of the HPV-ls URR by YY1 in an extended nu mber of cell lines. Except for HeLa cells, YY1 represses or does not i nfluence oncogene expression in all cell lines tested. In HeLa cells t he activation of viral oncogene expression by YY1 is caused by the fun ctional interplay between YY1 and a factor binding to the newly identi fied ''switch region'' of the HPV-18 URR. In this work we show that in HeLa cells, a 22 bp region located between the ''switch region'' and the promoter proximal fragment contributes to the modulation of the ac tivity of YY1 and, in addition, regulates HPV-18 promoter activity ind ependently of YY1.