Antisense targeting of E6AP elevates p53 in HPV-infected cells but not in normal cells

Abstract

Invasive cervical cancer is very highly correlated with the presence of high-risk human papillomavirus (HPV) types 16 and 18. Two viral proteins, E6 and E7, act in concert to subvert growth control of infected cells by inactivating the tumor suppressor proteins, p53 and Rb, respectively. E6 is thought to abrogate p53 function by stimulating its degradation via ubiquitin-mediated proteolysis in a reaction requiring E6AP (E6-Associated Protein). Here we evaluate the in vivo role of E6AP in p53 degradation in normal and HPV-infected cell types using antisense phosphorothioate oligodeoxynucleotides (S-ODNs). This study shows that reduction of E6AP in vivo in high-risk HPV-infected cells leads to an elevation of p53, confirming the function of E6AP predicted by in vitro experiments. Further, we demonstrate that reduction of E6AP in normal cells has no effect on p53 levels, indicative of an E6AP-indpendent mechanism for p53 degradation. These experiments show that inhibition of intermediate proteins in the ubiquitin-mediated proteolysis pathway (ubiquitin-conjugating enzymes or associated recognition proteins) can result in specific inhibition of substrate degradation. We propose that modulation of p53 levels by elimination of E6AP function may have therapeutic potential for cervical cancer.