Control of HPV 18 DNA replication by cellular and viral transcription factors

Papillomavirus replication in vivo requires the interaction of the virally encoded proteins E1 and E2 with the origin of replication which is localised in the regulatory region (long control region or LCR) of the viral genome. In genital human papillomaviruses (HPVs), the origin overlaps promoter elements of early transcription. In this study, we analysed the replication of HPV18 DNA using the complete LCR containing mutations in transcription regulatory elements. We found that each of the three E2 binding sites proximal to the AT-rich sequence of the origin contributes to the replication rate of DNA, although not identically. In addition, two sequences important for early transcription, an Sp1 binding site and the TATA box, were also found to play a role in replication. In contrast, two AP1 binding sites required for the enhancer-mediated activation of early transcription did not affect the replication, while other upstream sequences in the LCR did contribute to the replication efficiency. Our results indicate that besides a core origin of replication containing an AT-rich sequence and three E2 binding sites, auxiliary elements affect HPV18 DNA replication in the context of the full length LCR, some of which are important for transcription.