Transcriptional enhancer factor (TEF)‐1 and its cell‐specific co‐activator activate human papillomavirus‐16 E6 and E7 oncogene transcription in keratinocytes and cervical carcinoma cells

The human papillomavirus (HPV)‐16 oncogenes, E6 and E7, are transcribed preferentially in keratinocytes and cervical carcinoma cells due to a 5′ enhancer. An abundant peptide binding to a 37 nt enhancer element was purified from human keratinocytes by sequence‐specific DNA chromatography. This protein was identified as transcriptional enhancer factor (TEF)‐1 by complex mobility, binding to wild‐type and mutant SV40 and HPV‐16 enhansons and antigenic reactivity with two anti‐TEF‐1 antibodies. TEF‐1 is cell‐specific, but its transactivation also depends on a limiting, cell‐specific TEF‐1 ‘co‐activator’. We show that both TEF‐1 and the TEF‐1 co‐activator are active in human keratinocytes and essential for HPV‐16 transcription. TEF‐1 binding in vivo was necessary for HPV‐16 P97 promoter activity. Excess TEF‐1 and chimeric GAL4‐TEF‐1 specifically inhibited the P97 promoter by ‘squelching’, indicating that HPV‐16 transcription also requires a limiting TEF‐1 co‐activator. TEF‐1 and the TEF‐1 co‐activator functions mirrored HPV‐16 transcription by their presence in keratinocytes and cervical carcinoma cells and their absence from lymphoid B‐cells, but also functioned in liver cells where the HPV‐16 promoter is inactive. TEF‐1 and its associated co‐activator are thus part of a complex mechanism which determines the restricted cell range of the HPV‐16 E6 and E7 oncogene promoter.