UP-REGULATION OF HORMONE RESPONSE OF HUMAN PAPILLOMAVIRUS TYPE-16 EXPRESSION AND INCREASED DNA-PROTEIN BINDING BY CONSENSUS MUTATIONS OF VIRAL GLUCOCORTICOID RESPONSE ELEMENTS

Human papillomaviruses (HPVs) and steroid hormones are linked to the d evelopment of cervical cancer. Studies from our laboratory and others showed that the steroid glucocorticoid and progesterone hormones activ ated the expression of HPV type 16. This activation was attributed to the specific interaction of the glucocorticoid receptor (GR) with the three glucocorticoid response elements (GREs) in the HPV16 regulatory region. In the present study, we first examined the glucocorticoid res ponse mediated through the GREs, using GRE consensus (GREc) mutations and expression assays from a heterologous basal promoter. Both single and triple HPV16 GREc constructs increased expression in the presence of the dexamethasone glucocorticoid in HeLa cervical carcinoma cells a nd primary baby rat kidney epithelial cells, in comparison with the tr iple wildtype GREs. Further, the hormone increased significantly the e xpression of the viral E6-E7 oncogene mRNA from intact HPV in primary human ectocervical cells in in situ hybridization assays. Three in vit ro assays of DNA-protein interaction with oligonucleotides and HeLa ce ll extracts showed a higher binding of protein to two of the HPV16 GRE cs than to the wild-type GREs. This applied especially to the GRE cont aining an overlapping NF1 half site, that also had a greater different ial induction by dexamethasone of expression in vivo. The NF1 site was mutated in the GREc that also was bound by unique, lower-mobility com plexes in electrophoretic mobility shift assays. UV-crosslinking assay s confirmed the increased binding and showed binding by a 96-kDa prote in, probably the GR. Our results show an important role of glucocortic oids in HPV16 expression. The direct action through the HPV16 GREs is suggested to be mediated by the hormone-activated GR in association wi th other factors. (C) 1996 Wiley-Liss, Inc.