Figure 4. HPV E7 enables SiHa cervical cancer cell survival via up-regulation of SIRT1 protein levels.. (A) Equal amounts of protein analysed by immunoblotting as indicated, upper panels SiHa cells (50 μg protein). Bottom panel HCT116 cell positive control for p53 K382Ac detection (40 μg protein, 2 minute exposure). Note that p53 K382Ac is undetectable in SiHa cells (5 min exposure) and requires 2 h exposure for detection (†). (B) Relative levels of SIRT1, SIRT1 S47P and SIRT1 S27P 48h post-transfection with indicated siRNAs, mean of two experiments. (C) Phase contrast images of SiHa cells post-transfection with the indicated siRNAs. (D) Apoptotic SiHa cells 48h post-transfection with the indicated siRNAs. (E) Primary human keratinocytes 48h post-transfection with expression vectors for HPV E6 and HPV16 E7 and equivalent samples immunoblotted for HPV E6, HPV E7, SIRT1, SIRT1 S27P and SIRT1 S47P.