E5 proteins of human papillomavirus types 11 and 16 transactivate the c-fos promoter through the NF1 binding element

Human papillomavirus type II (HPV-11) and HPV-16 contain an E5 gene that can induce c-Sos gene expression in mouse fibroblasts. This study investigated the human c-fos promoter characteristics by mapping the c-Sos promoter sequence with several deletion and point mutants that confer responsiveness to E5 of HPV-11 or HPV-16. The mutant studies show that NF1 binding sequences within the c=fos promoter were crucial for the induction of the c-fos gene by E5, and the gel shift assay study suggested that E5 of both HPV-11 and HPV-16 is associated, perhaps indirectly with this NF1 element in the transactivation of the human c-Sos promoter, Using an inducible system, me demonstrate that increased induction of the HPV-11 E5 gene in cells led to increased transactivation of the NF1 element. In addition, the transactivating activity of a series of HPV-11 E5 mutants on the NF1 element had a strong correlation with their respective transforming activities.