Localization of human papillomavirus type 16 E6 protein and hDaxx in a human cervical carcinoma cell line HeLa and their effects on cell apoptosis / 中华皮肤科杂志

ABSTRACT

ObjectiveTo determine the subcellular localization of exogenous human papillomavirus type 16 E6 protein(HPV16 E6) and hDaxx in HeLa cells and their effects on tumor necrosis factor (TNF)-α-induced apoptosis.MethodsHeLa cells were transfected with plasmids pDsRed-monomer-C1/HPV16 E6,pEGFP-CI/hDaxx,pEGFP-C1 and pDsRed-monomer-C1 respectively.Subsequently,Western blot was carried out to quantify the expression of fusion proteins DsRed-HPV16E6 and EGFP-hDaxx in transfected cells,and laser scanning confocal microscopy to observe the subcellular distribution of HPV16 E6 protein and hDaxx.Some HeLa cells were divided into 5 groupsuntransfected (control group),untransfected and treated with TNF-α(TNF-ot group),transfected with pcDNA3.1 (-) and treated with TNF-α(empty vector group),transfected with pcDNA3.1 (-)/HPV16 E6 and treated with TNF-α (HPV16 E6 group),cotransfected with pcDNA3.1(-)/HPV16 E6 and pcDNA3.1 (-)/hDaxx and treated with TNF-α (cotransfected group).After additional culture,the cells were collected and subjected to flow cytometry(FCM) to evaluate the apoptosis of cells as well as spectrophotometry to determine the relative activity of Caspase-8 and Caspase-3.ResultsWestern blot showed that both DsRed-HPV16 E6 and EGFP-hDaxx were expressed in HeLa cells.In Hela cells transfected with pDsRedmonomer-C1/HPV16 E6 or pEGFP-C1/hDaxx alone,the red fluorescence of HPV16 E6 was observed in the nucleus and cytoplasm,while the green fluorescence of hDaxx only in the nucleus; in those cotransfected with pDsRed-monomer-C1/HPVl6 E6,HPV16 E6 and hDaxx proteins were regionally aggregated near the nuclear membrane in nuclei,and hDaxx was partly translocated from the nucleus to the cytoplasm.The apoptosis rate and relative activity of Caspase-8 and Caspase-3 were statistically lower in HPV16 E6 group than in the empty vector group and cotransfected group(21.4％ ± 1.1％ vs.27.0％ ± 0.9％ and 32.5％ ± 2.1％,0.057 ± 0.003 vs.0.092 ±0.012 and 0.109 ± 0.013,0.054 ± 0.006 vs.0.093 ± 0.005 and 0.110 ± 0.004,all p＜ 0.01).Conclusions HPV16 E6 protein induces the partial translocation of hDaxx from the nucleus into the cytoplasm and colocalizes with hDaxx in the cells.The apoptosis of HeLa cells induced by TNF-α can be suppressed by HPV16 E6 protein,while the overexpression of hDaxx can attenuate the suppressing effect of HPV16 E6 protein on apoptosis in Hela cells.