Expression of human papillomavirus types 16 and 18 DNA sequences in cervical carcinoma cell lines

A total of six cervical carcinoma cell lines, of which two contained human papillomavirus (HPV) type 16 and four contained HPV type 18 DNA, were examined for viral RNA expression by spot‐blot hybridization. All six cell lines contained HPV‐specific cytoplasmic poly(A)‐containing RNA. The same RNA species were detected in both cytoplasmic and polysomal fractions, indicating nonselective translation of these messages into protein products. Primer extension analysis of RNA from the cell lines revealed the presence of three major start sites at the 5′ end of the E6 gene for RNA from HPV 16‐containing cell lines and four major start sites at the 5′ end of the E6 gene for RNA from HPV 18‐containing cell lines. One cell line, ME 180, had a distinct pattern with only one minor HPV 18 start site. Northern‐blot hybridization using the E6‐E7 region of HPV 16 and 18 DNAs as probes revealed the presence of E6‐E7 transcripts in all the cell lines except ME 180. Southern‐blot analysis revealed that while sequences hybridizing to the E6‐E7 coding region were present, the 5′ end region containing the enhancer‐promoter region of viral DNA is deleted in ME 180. Subsequent Northern‐blot hybridization using the E1 region of HPV 18 DNA as probe revealed that the viral RNA in ME 180 is transcribed from this region.