HPV16 E6 expression activates mTOR1, 4E-BP1, S6K, and S6 phosphorylation through a TSC2-independent mechanism. (A) Schematic diagram of mTORC1 signaling. See text for details. (B to E) Western blot analysis of mTOR phosphorylation (B), TSC2 expression (with quantifications shown below) (C), 4E-BP1 phosphorylation (D), and S6K and S6 phosphorylation (E) in HPV16 E6-expressing and control RKO cells. A p53 blot is shown in panel B to document HPV16 E6 expression, and actin blots are shown as loading controls. Also shown are results from Western blot analysis of 4E-BP1 (F) and TSC2 expression and S6K and S6 phosphorylation (G) (with quantifications shown below) in HPV16 E6-expressing and control (LX) primary human foreskin keratinocyte cultures (HFKs). A p53 blot is shown in panel F to document HPV16 E6 expression, and actin blots are shown as loading controls.