FIG. 5.

Alternative cell fates of HPV-18 URR-E7-transduced keratinocytes during squamous differentiation. (A) Kinetic profiles of percentages of differentiated keratinocytes doubly positive for ³H-TdR and BrdU (open triangles), for ³H-TdR and cyclin E (filled squares), or for ³H-TdR and p27kip1 (open circles) in E7-transduced cultures. The data were taken from Fig. 1A, and 4A. (B) Proposed model of alternative paths induced by HPV-18 E7 in differentiated keratinocytes. Lightly shaded ovals represent nuclei capable of entering S phase, whereas filled ovals represent nuclei accumulating abundant p27kip1 or cyclin E/p21cip1 as well. The size of the nucleus reflects its DNA content. Nuclear division without cytokinesis generates binucleated cells. Attrition of cells to the lower path leads to low and decreasing percentages of cells capable of entering into one or more rounds of S phase.