“…HPV1, 5, 8, 11, 16, 18, 31, and 49 E8^E2 ko genomes replicate to much higher levels than wild-type (wt) genomes in short-term assays in immortalized human keratinocytes (HPV16, 31), normal human keratinocytes (HPV1, 8, 16, 31, 49), or the U2OS osteosarcoma cell line (HPV5, 11, 18) [ 8 , 14 , 20 , 23 , 27 , 39 , 40 , 41 , 42 ]. Furthermore, MmuPV1 E8^E2 ko genomes display greatly increased viral gene expression in cultured murine keratinocytes similar to HPV E8^E2 ko in human keratinocytes suggesting that E8^E2 function is conserved among human and animal PVs [ 43 ]. Evolutionary conservation, viral mutants and complementation assays strongly indicate that the E8^E2 fusion protein is responsible for the phenotypes of PV E8^E2 mutants: (1) Disruption of the E8 exon splice donor site, the E8 ATG, or translation termination linker (TTL) mutants in E8 result in increased genome replication [ 14 ], arguing that the spliced E8^E2 product is responsible.…”