Figure 4.

Biological activity of the E7 proteins of HPV16 lineage A variants. (A) Schematic representation of the HPV16 E7 protein. The LXCXE motif required for degradation of the retinoblastoma protein (pRb) and amino acid residues characteristic for A1, A4, and A5 are shown. (B) Western blot analyses of cell extracts from E7-transduced human cervical keratinocytes. Representative results of three independent experiments are shown in the left panel. Expression levels of pRb and PTPN14 were quantified as the relative band intensity of each protein adjusted with that of α-tubulin, and the average and standard deviation of the three experiments are shown in the right panel. No significant difference was observed for pRb levels between A1 and A5 (p = 0.23, paired t-test).