Differential regulation by c-jun and c-fos protooncogenes of hormone response from composite glucocorticoid response element in human papilloma virus type 16 regulatory region.

Glucocorticoid hormones positively regulate human papilloma virus (HPV) type 16 gene expression, and we have previously shown that this regulation is through three glucocorticoid response elements (GREs). The GRE at nucleotide 7640 is a composite GRE (cGRE) containing an overlapping activator protein-1 (AP-1) motif for the c-jun homodimer and c-jun/c-fos heterodimer. This report examined the effects of c-jun and/or c-fos AP-1 protooncogenes and the glucocorticoid hormone dexamethasone on expression of the HPV 16 cGRE in AP-1-deficient P19 embryonal carcinoma cells. The activity of the full-length HPV 16 enhancer was progressively increased with increasing levels of c-jun. The hormone induced an additional response. For the c-jun/c-fos heterodimer, the response to hormone was progressively diminished. Site-specific mutations of the cGRE revealed that the regulation by AP-1 and hormone required both GRE and the AP-1 motif. An enhancer fragment containing the cGRE and excluding the two simple GREs gave similar results. Two disruption mutations of the AP-1 site confirmed the requirement of this site for hormone response. A cGRE oligonucleotide construct substantiated the effect of c-jun for response to hormone. For heterodimer, activity and hormone response were both also progressively increased. The results reveal a unique cross-talk between the distinct AP-1- and hormone-signaling pathways, suggesting the involvement of a complex interaction of c-jun and c-fos and glucocorticoid hormone receptor with the HPV 16 cGRE, resulting in novel control patterns for regulating viral expression.