Transcription patterns of human papillomavirus type 16 in genital intraepithelial neoplasia: evidence for promoter usage within the E7 open reading frame during epithelial differentiation

Human papillomavirus (HPV) type 16 transcription was analysed by in situ hybridization using 125I-labelled subgenomic riboprobes, from 26 genital intraepithelial neoplastic (IN) lesions, in formalin-fixed biopsies from 18 different cases. Distinct transcription patterns separable by the presence or absence of late gene transcription were detected. In 12 lesions, late gene expression was absent; HPV transcripts corresponding to the E6 and E7 open reading frame (ORF) were detectable in all basal cells and were usually evenly distributed through all layers of the epithelium. Transcripts corresponding to the E1, E2 and E2/E4 ORFs were present in nine of 12 lesions and displayed a similar distribution. In 14 lesions late gene transcripts were present. E6 and E7 transcripts were detectable basally in all but one lesion. The levels of E7 but not E6 transcripts were markedly increased in the superficial cells of differentiating epithelia, with an identical distribution and at similar levels to those of the E2/E4 transcript. We propose that the most abundant transcript in genital IN lesions containing late gene expression is an E7/E1 [symbol: see text] E2/E4 transcript corresponding to that reported in HPV-6/11 condylomata and which is derived from a similar promoter within the E7 ORF.