title: Cadmium delays non-homologous end joining (NHEJ) repair via inhibition of DNA-PKcs phosphorylation and downregulation of XRCC4 and Ligase IV.
abstract: Although studies have shown that cadmium (Cd) interfered with DNA damage repair (DDR), whether Cd could affect non-homologous end joining (NHEJ) repair remains elusive. To further understand the effect of Cd on DDR, we used X-ray irradiation of Hela cells as an in vitro model system, along with γH2AX and 53BP1 as markers for DNA damage. Results showed that X-ray significantly increased γH2AX and 53BP1 foci in Hela cells (p < 0.01), all of which are characteristic of accrued DNA damage. The number of foci declined rapidly over time (1-8h postirradiation), indicating an initiation of NHEJ process. However, the disappearance of γH2AX and 53BP1 foci was remarkably slowed by Cd pretreatment (p < 0.01), suggesting that Cd reduced the efficiency of NHEJ. To further elucidate the mechanisms of Cd toxicity, several markers of NHEJ pathway including Ku70, DNA-PKcs, XRCC4 and Ligase IV were examined. Our data showed that Cd altered the phosphorylation of DNA-PKcs, and reduced the expression of both XRCC4 and Ligase IV in irradiated cells. These observations are indicative of the impairment of NHEJ-dependent DNA repair pathways. In addition, zinc (Zn) mitigated the effects of Cd on NHEJ, suggesting that the Cd-induced NHEJ alteration may partly result from the displacement of Zn or from an interference with the normal function of Zn-containing proteins by Cd. Our findings provide a new insight into the toxicity of Cd on NHEJ repair and its underlying mechanisms in human cells.
authors.affiliation: Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Li
authors.affiliation: Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Xueyan
authors.initials: X
authors.lastname: Gu
authors.affiliation: Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Jinxin
authors.initials: J
authors.lastname: Kong
authors.affiliation: Gansu Key laboratory of Space Radiobiology, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Ding
authors.affiliation: Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Qi
authors.affiliation: Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Yingmei
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Gansu Key laboratory of Space Radiobiology, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Jufang
authors.initials: J
authors.lastname: Wang
authors.affiliation: Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Lanzhou 730000, China. Electronic address: huangdj@lzu.edu.cn.
authors.forename: Dejun
authors.initials: D
authors.lastname: Huang
mesh_terms: D002104:Cadmium / Q000633:toxicity*; D004249:DNA Damage / Q000187:drug effects; D059766:DNA End-Joining Repair / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000096:biosynthesis* / Q000235:genetics; D051747:DNA-Activated Protein Kinase / Q000096:biosynthesis* / Q000235:genetics; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects; D006367:HeLa Cells; D006657:Histones / Q000096:biosynthesis; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000096:biosynthesis; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D000071857:Tumor Suppressor p53-Binding Protein 1; D014965:X-Rays
chemical_list: D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; C000607893:LIG4 protein, human; C498301:TP53BP1 protein, human; D000071857:Tumor Suppressor p53-Binding Protein 1; C101467:XRCC4 protein, human; D002104:Cadmium; D051747:DNA-Activated Protein Kinase; D011088:DNA Ligases; D000072481:DNA Ligase ATP
keywords: DNA Ligase IV; DNA damage repair (DDR); DNA-dependent protein kinase; Heavy metal cadmium (Cd); Non-homologous end joining (NHEJ); X-ray cross-complementing protein 4