HFFs with stable expression of empty vector (C), HPV16 E7 (E7), HPV16 E7Δ21-24 (Δ21-24), or HPV16 E7Δ79-83 (Δ79-83) were collected at different times after release from a double thymidine block. Shown here is a representative experiment; similar results were obtained in three additional experiments with different HFF populations. (A) Western blot analysis of E7 expression in the stable HFF populations. (B) Western blot analyses of pRB, pH3S10, histone H3, cyclin B and actin are shown. Cyclin B quantifications relative to actin are indicated above the cyclin B blot. Values are presented relative to the highest (1) in C, HPV16 E7, HPV16 E7Δ21-24, or HPV16 E7Δ79-83 expressing cells. (C) FACS analyses of G2/M cell populations are shown for HFF C, HPV16 E7, HPV16 E7Δ21-24, and HPV16 E7Δ79-83 expressing cells at different times after release from a double thymidine block.