title: APE1/Ref-1 enhances DNA binding activity of mutant p53 in a redox-dependent manner.
abstract: Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a dual function protein; in addition to its DNA repair activity, it can stimulate DNA binding activity of numerous transcription factors as a reduction-oxidation (redox) factor. APE1/Ref-1 has been found to be a potent activator of wild-type p53 (wtp53) DNA binding in vitro and in vivo. Although p53 is mutated in most types of human cancer including hepatocellular carcinoma (HCC), little is known about whether APE1/Ref-1 can regulate mutant p53 (mutp53). Herein, we reported the increased APE1/Ref-1 protein and accumulation of mutp53 in HCC by immunohistochemistry. Of note, it was observed that APE1/Ref-1 high-expression and mutp53 expression were associated with carcinogenesis and progression of HCC. To determine whether APE1/Ref-1 regulates DNA binding of mutp53, we performed electromobility shift assays (EMSAs) and quantitative chromatin immunoprecipitation (ChIP) assays in HCC cell lines. In contrast to sequence-specific and DNA structure-dependent binding of wtp53, reduced mutp53 efficiently bound to nonlinear DNA, but not to linear DNA. Notably, overexpression of APE1/Ref-1 resulted in increased DNA binding activity of mutp53, while downregulation of APE1/Ref-1 caused a marked decrease of mutp53 DNA binding. In addition, APE1/Ref-1 could not potentiate the accumulation of p21 mRNA and protein in mutp53 cells. These data indicate that APE1/Ref-1 can stimulate mutp53 DNA binding in a redox-dependent manner.
authors.affiliation: Cancer Center, Daping Hospital and Research Institute of Surgery, Third Military Medical University, Chongqing, P.R. China.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Cun
authors.affiliation: Cancer Center, Daping Hospital and Research Institute of Surgery, Third Military Medical University, Chongqing, P.R. China.
authors.forename: Nan
authors.initials: N
authors.lastname: Dai
authors.affiliation: Cancer Center, Daping Hospital and Research Institute of Surgery, Third Military Medical University, Chongqing, P.R. China.
authors.forename: Mengxia
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Orthopedics, Wuhan General Hospital, Guangzhou Military Area Command, Wuhan, P.R. China.
authors.forename: Chengjie
authors.initials: C
authors.lastname: Xiong
authors.affiliation: Cancer Center, Daping Hospital and Research Institute of Surgery, Third Military Medical University, Chongqing, P.R. China.
authors.forename: Qinhong
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Cancer Center, Daping Hospital and Research Institute of Surgery, Third Military Medical University, Chongqing, P.R. China.
authors.forename: Jiangdong
authors.initials: J
authors.lastname: Sui
authors.affiliation: Cancer Center, Daping Hospital and Research Institute of Surgery, Third Military Medical University, Chongqing, P.R. China.
authors.forename: Chengyuan
authors.initials: C
authors.lastname: Qian
authors.affiliation: Cancer Center, Daping Hospital and Research Institute of Surgery, Third Military Medical University, Chongqing, P.R. China.
authors.forename: Dong
authors.initials: D
authors.lastname: Wang
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000235:genetics*; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics; D004247:DNA / Q000378:metabolism*; D004260:DNA Repair / Q000235:genetics; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018450:Disease Progression; D005260:Female; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010084:Oxidation-Reduction; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D015533:Transcriptional Activation / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D004247:DNA; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase