title: Nm23-H1 protein binds to APE1 at AP sites and stimulates AP endonuclease activity following ionizing radiation of the human lung cancer A549 cells.
abstract: Non-metastatic protein-23 homolog-1 (Nm23-H1) is a multifunctional protein with DNase and histidine protein kinase activities. Human apurinic endonuclease-1 (APE1) is the AP endonuclease DNA base excision repair (BER) enzyme involved in several important cellular functions. Since the relationship between Nm23-H1 and APE1 proteins is unclear, we evaluated their interaction at different time points after irradiating human lung cancer A549 cells with X-rays. We found that Nm23-H1 and APE1 overexpression was induced by irradiation in a dose- and time-dependent manner. Subcellular distribution pattern of both proteins was reversed after irradiation. After irradiation, APE1 that initially showed nuclear localization was gradually increased in the cytoplasm, whereas Nm23-H1 that mainly showed cytoplasmic localization was gradually increased in the nuclei of A549 cells. Nm23-H1 and APE1 interaction was demonstrated by His-pull-down and co-immunoprecipitation assays. The presence of Nm23-H1/APE1 complex in X-ray-irradiated A549 cells was also detected by DNA affinity precipitation analysis of a DNA fragment containing an AP site. Although the AP endonuclease activity of Nm23-H1 was too weak to be detected, the AP endonuclease activity of APE1 was increased with the enhanced Nm23-H1 expression. In conclusion, our data point to a mechanism by which Nm23-H1 protects cells against oxidative stress through the engagement of DNA BER enzyme APE1.
authors.affiliation: Cancer Center, Institute of Surgical Research, Daping Hospital, Third Military Medical University, Chongqing 400042, China.
authors.forename: Zhi-Min
authors.initials: ZM
authors.lastname: Zhang
authors.forename: Xue-Qin
authors.initials: XQ
authors.lastname: Yang
authors.forename: Dong
authors.initials: D
authors.lastname: Wang
authors.forename: Ge
authors.initials: G
authors.lastname: Wang
authors.forename: Zhen-Zhou
authors.initials: ZZ
authors.lastname: Yang
authors.forename: Yi
authors.initials: Y
authors.lastname: Qing
authors.forename: Zhi-Xiang
authors.initials: ZX
authors.lastname: Yang
authors.forename: Meng-Xia
authors.initials: MX
authors.lastname: Li
authors.forename: De-Bing
authors.initials: DB
authors.lastname: Xiang
mesh_terms: D045744:Cell Line, Tumor; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D055785:Gene Knockdown Techniques; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism / Q000528:radiation effects; D008175:Lung Neoplasms / Q000235:genetics / Q000473:pathology*; D008958:Models, Molecular; D054778:NM23 Nucleoside Diphosphate Kinases / Q000235:genetics / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D011485:Protein Binding / Q000528:radiation effects; D021381:Protein Transport / Q000528:radiation effects; D011836:Radiation Tolerance / Q000235:genetics; D013997:Time Factors; D014965:X-Rays / Q000009:adverse effects
chemical_list: D054778:NM23 Nucleoside Diphosphate Kinases; D004247:DNA; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase