Fig 9.

HPV DNA replication is attenuated in N40-expressing stable cell lines. (A) Colony formation assay. C33A cells were transfected with the indicated expression vectors and then selected for approximately 3 weeks in bleomycin-containing media. Drug-resistant colonies were fixed with methanol and stained with methylene blue. (B) Western blot showing the expression of the N40, WT, or p80-binding mutant protein (WF, VE, and VI), in the established stable cell lines. β-Tubulin was used as a loading control. (C) The DNA replication activities of WT E1 were tested by transfecting three different quantities of E1 expression vector (2.5, 5, and 10 ng) in the indicated N40 stable cell lines. DNA replication was also measured in a control cell line expressing YFP alone (ctl). DNA replication activity is reported as a percentage of the signal obtained with 10 ng of WT E1 expression vector in the control cell line. The error bars represent the standard deviations of duplicate values. The results are representative of at least three independent experiments.