Human papillomavirus type 16 immortalized cervical keratinocytes contain transcripts encoding E6, E7, and E2 initiated at the P97 promoter and express high levels of E7.

Abstract

Human cervical keratinocytes represent the specific host for the genital human papillomaviruses (HPV). Transfection of these cells with the DNA of a number of the oncogenic HPVs including type 16 was recently shown to result in their immortalization but not in malignant transformation. In this report we show that viral transcripts for E6 and E7 in these cells were as abundant as in cancer derived cell lines. However, in contrast to cancer derived cell lines, immortalized cervical keratinocytes contained RNA with the potential to encode a full-length E2 protein. In addition, the levels of the E7 oncoprotein were at least as high as in cancer derived cell lines, suggesting that E2 interruption, observed in cancer derived cell lines, is not causally related to the high level of E7 expression and, therefore, deregulation of the P97 promoter may not be a prerequisite for HPV-16 associated cancer development. Furthermore, we show that E6, E7, and E2 encoding transcripts all originate from the viral promoter, P97. Unlike in cancer derived cell lines, all transcripts terminated at the early poly(A) site.