HPV 5 and 8 E6 Abrogate ATR activity resulting in increased persistence of UVB induced DNA damage

The role of the e6 oncoprotein from high-risk members of the α human papillomavirus genus in anogenital cancer has been well established. however,far less is known about the e6 protein from the β human papillomavirus genus (β-hpvs). some β-hpvs potentially play a role in non-melanoma skin cancer development,although they are not required for tumor maintenance. instead,they may act as a co-factor that enhances the carcinogenic potential of uv damage. indeed,the e6 protein from certain β-hpvs (hpv 5 and 8) promotes the degradation of p300,a histone acetyl transferase involved in uv damage repair. here,we show that the expression of hpv 5 and 8 e6 increases thymine dimer persistence as well as the likelihood of a uvb induced double strand break (dsb). importantly,we provide a mechanism for the increased dna damage by showing that both extended thymine dimer persistence as well as elevated dsb levels are dependent on the ability of hpv 8 e6 to promote p300 degradation. we further demonstrate that hpv 5 and 8 e6 expression reduces the mrna and protein levels of atr,a pi3 kinase family member that plays a key role in uv damage signaling,but that these levels remain unperturbed in cells expressing a mutated hpv 8 e6 incapable of promoting p300 degradation. we confirm that the degradation of p300 leads to a reduction in atr protein levels,by showing that atr levels rebound when a p300 mutant resistant to hpv 8 mediated degradation and hpv 8 e6 are co-transfected. conversely,we show that atr protein levels are reduced when p300 is targeted for degradation by sirna. moreover,we show the reduced atr levels in hpv 5 and 8 e6 expressing cells results in delayed atr activation and an attenuated ability of cells to phosphorylate,and as a result accumulate,p53 in response to uvb exposure,leading to significantly reduced cell cycle arrest. in conclusion,these data demonstrate that β-hpv e6 expression can enhance the carcinogenic potential of uvb exposure by promoting p300 degradation,resulting in a reduction in atr levels,which leads to increased thymine dimer persistence and increased uvb induced dsbs. © 2012 wallace et al.