FIG 6.

Infectious internalization kinetics of HPV16 are unaffected by cell cycle synchronization. (A) Schematic depiction of cell cycle synchronization by double thymidine block. (B) Synchronized and nonsynchronized cells were fixed with ethyl alcohol (EtOH) and analyzed for their cell cycles states at different times postrelease. Cell cycle phases were designated according to cellular DNA content by PI staining and flow-cytometric analysis. G₁, a single set of chromosomes (i.e., DNA content = 1); G₂/M, duplicated chromosomes (DNA content = 2); S, replicating chromosomes between the two states. Shown are the values from two independent experiments. (C) Infectious internalization of HPV16 (upper panels) and FPC-HPV16 (lower panels) with synchronized (black dotted line) and nonsynchronized (gray dotted line) cells was analyzed in add-on experiments. Cells were infected at 2 h, 6 h, or 14 h postrelease from thymidine block. Curves were fitted with the nonlinear regression function of GraphPad Prism v6. Relative infectious internalization values were normalized to 48-h infection samples and are depicted as percentages ± SEM.