Hypermethylation of the human papillomavirus transgenome in transgenic mice

We have previously reported an observation that the regulatory sequence of the human papillomavirus (HPV) type 18 genome elicits only basal and unregulated transcriptional activities in transgenic mice [Choo et al., Virology (1992) 188:378-383]. We have now extended the study to other transgenic mice carrying an entire or a subgenomic fragment of HPV-16 and -18. Extremely low levels of HPV transcripts were detected in various organs of the mice only by reverse transcriptase-based polymerase chain reaction. On analysis of the methylation status of the HPV transgenome sequences, hypermethylation was clearly observed, therefore suggesting a possible explanation for low level HPV transgenome transcriptional activity in HPV transgenic mice.