NOVEL BINDING-SITES FOR REGULATORY FACTORS IN THE HUMAN-PAPILLOMAVIRUS TYPE-18 ENHANCER AND PROMOTER IDENTIFIED BY IN-VIVO FOOTPRINTING

The E6 and E7 genes of human papillomaviruses (HPVs) associated with a nogenital cancers are largely responsible for the oncogenic activity o f these viruses, and regulation of these genes has been intensively st udied. Transcription of the E6 and E7 genes is controlled by the viral upstream regulatory region (URR). We have used in vivo footprinting t o examine the occupancy by regulatory factors of the HPV type 18 (HPV1 8) URR enhancer and promoter in the cervical carcinoma cell lines HeLa and C4-IL. While corroborating occupancy in vivo of all of the elemen ts previously implicated in the transcriptional control of the HPV18 E 6 and E7 genes by in vitro DNase I footprinting, gel retardation assay s, and transfection studies, we also detect occupancy in vivo of sever al enhancer and promoter sequences which have not been previously iden tified as HPV18 URR regulatory elements. Our data suggest that the HPV 18 enhancer and promoter are more densely occupied by DNA-binding prot eins than previously thought and raise the possibility that additional , possibly novel factors contribute to transcription of the HPV18 earl y genes.