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Evaluating the Extent of LINE-1 Mobility Following Exposure to Heavy Metals in HepG2 Cells

Biological Trace Element Research volume 160, pages 143–151 (2014)Cite this article

Abstract

The long interspersed elements-1 (LINE1 or L1 retrotransposon) constitute 17 % of the human genome and retain mobility properties within the genome. At present, 80–100 human L1 elements are thought to be active in the genome. The mobilization of these active elements may be influenced upon exposure to the heavy metals. In the present study, we evaluated the association of aluminum, lead, and copper exposure with L1 retrotransposition in human hepatocellular carcinoma (HepG2) cell line. An in vitro retrotransposition assay using an enhanced green fluorescent protein (EGFP)-tagged L1RP cassette was established to track EGFP shining as the mark of retrotransposition. Following determination of noncytotoxic concentrations of these metals, pL1RP-EGFP-transfected HepG2 cells were subjected to long-term treatment. Flow cytometry analysis of cells treated with various concentrations of these metals along with quantitative real-time PCR was used to quantify L1 retrotransposition frequencies. Aluminum significantly increased L1 retrotransposition frequency, while no significant association was found concerning lead exposure and L1 retrotransposition. Copper treatment downregulated L1 retrotransposition as a result of EGFP-tagged L1RP expression. Our findings suggest that aluminum might have the potential to cause genomic instability by the enhancement of L1 mobilization. Thus, the risk of induced L1 retrotransposition should be considered during drug safety evaluation and risk assessments of exposure to toxic environmental agents. Further studies are needed for a more robust assay to evaluate any associations between long-term lead exposure and L1 mobility in cell culture assay.

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References

  1. Athanikar JN, Morrish TA, Moran JV (2002) Of man in mice. Nat Genet 32(4):562–563

    CAS  PubMed  Article  Google Scholar 

  2. Coufal NG (2008) Evidence for L1 retrotransposition in the human nervous system. University of California, San Diego, Dissertation

    Google Scholar 

  3. Cordaux R, Batzer MA (2009) The impact of retrotransposons on human genome evolution. Nat Rev Genet 10(10):691–703

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  4. Lander ES, Linton LM, Birren B, Nusbaum C, Zody MC, Baldwin J et al (2001) Initial sequencing and analysis of the human genome. Nature 409(6822):860–921

    CAS  PubMed  Article  Google Scholar 

  5. Babushok DV, Kazazian HH Jr (2007) Progress in understanding the biology of the human mutagen LINE-1. Hum Mutat 28(6):527–539

    CAS  PubMed  Article  Google Scholar 

  6. Kazazian HH Jr (2011) Mobile DNA: finding treasure in junk. FT Press Science, New Jersey

    Google Scholar 

  7. Deininger PL, Moran JV, Batzer MA, Kazazian HH Jr (2003) Mobile elements and mammalian genome evolution. Curr Opin Genet Dev 13(6):651–658

    CAS  PubMed  Article  Google Scholar 

  8. Hulme A, Kulpa D, Perez J, Moran JV (2006) The impact of LINE-1 retrotransposition on the human genome. In: Lupski J, Stankiewicz P (eds) Genomic Disorders. Humana Press, pp 35-55

  9. Konkel MK, Batzer MA (2010) A mobile threat to genome stability: the impact of non-LTR retrotransposons upon the human genome. Semin Cancer Biol 20(4):211–221

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  10. Symer DE, Connelly C, Szak ST, Caputo EM, Cost GJ, Parmigiani G, Boeke JD (2002) Human L1 retrotransposition is associated with genetic instability in vivo. Cell 110(3):327–338

    CAS  PubMed  Article  Google Scholar 

  11. Solyom S, Ewing AD, Rahrmann EP, Doucet T, Nelson HH, Burns MB, Harris RS, Sigmon DF, Casella A, Erlanger B, Wheelan S, Upton KR, Shukla R, Faulkner GJ, Largaespada DA, Kazazian HH Jr (2012) Extensive somatic L1 retrotransposition in colorectal tumors. Genome Res 22(12):2328–2338

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  12. Shukla R, Upton KR, Munoz-Lopez M, Gerhardt DJ, Fisher ME, Nguyen T, Brennan PM, Baillie JK, Collino A, Ghisletti S, Sinha S, Iannelli F, Radaelli E, Dos Santos A, Rapoud D, Guettier C, Samuel D, Natoli G, Carninci P, Ciccarelli FD, Garcia-Perez JL, Faivre J, Faulkner GJ (2013) Endogenous retrotransposition activates oncogenic pathways in hepatocellular carcinoma. Cell 153(1):101–111

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  13. McClintock B (1984) The significance of responses of the genome to challenge. Science (New York, NY) 226(4676):792–801

    CAS  Article  Google Scholar 

  14. Singer T, McConnell MJ, Marchetto MC, Coufal NG, Gage FH (2010) LINE-1 retrotransposons: mediators of somatic variation in neuronal genomes? Trends Neurosci 33(8):345–354

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  15. Ishizaka Y, Okudaira N, Tamura M, Iijima K, Shimura M, Goto M, Okamura T (2012) Modes of retrotransposition of long interspersed element-1 by environmental factors. Front Microbiol 3:191. doi:10.3389/fmicb.2012.00191

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  16. Farkash EA, Kao GD, Horman SR, Prak ET (2006) Gamma radiation increases endonuclease-dependent L1 retrotransposition in a cultured cell assay. Nucleic Acids Res 34(4):1196–1204

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  17. Teneng I, Montoya-Durango DE, Quertermous JL, Lacy ME, Ramos KS (2011) Reactivation of L1 retrotransposon by benzo(a)pyrene involves complex genetic and epigenetic regulation. Epigen Off J DNA Methylation Soc 6(3):355–367

    CAS  Article  Google Scholar 

  18. Morales JF, Snow ET, Murnane JP (2002) Environmental factors affecting transcription of the human L1 retrotransposon. I. Steroid hormone-like agents. Mutagenesis 17(3):193–200

    CAS  PubMed  Article  Google Scholar 

  19. Okudaira N, Okamura T, Tamura M, Iijma K, Goto M, Matsunaga A, Ochiai M, Nakagama H, Kano S, Fujii-Kuriyama Y, Ishizaka Y (2013) Long interspersed element-1 is differentially regulated by food-borne carcinogens via the aryl hydrocarbon receptor. Oncogene 32(41):4903–4912

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  20. Del Re B, Marcantonio P, Gavoci E, Bersani F, Giorgi G (2012) Assessing LINE-1 retrotransposition activity in neuroblastoma cells exposed to extremely low-frequency pulsed magnetic fields. Mutat Res 749(1–2):76–81

    PubMed  Google Scholar 

  21. Habibi L, Shokrgozar MA, Motamedi M, Akrami SM (2013) Effect of heavy metals on silencing of engineered long interspersed element-1 retrotransposon in nondividing neuroblastoma cell line. Iran Biomed J 17(4):171–178

    CAS  PubMed Central  PubMed  Google Scholar 

  22. Habibi L, Shokrgozar MA, Tabrizi M, Modaressi MH, Akrami SM (2013) Mercury specifically induces LINE-1 activity in a human neuroblastoma cell line. Mutat Res. doi:10.1016/j.mrgentox.2013.07.015

    Google Scholar 

  23. Baccarelli A, Bollati V (2009) Epigenetics and environmental chemicals. Curr Opin Pediatr 21(2):243–251

    PubMed Central  PubMed  Article  Google Scholar 

  24. Jarup L (2003) Hazards of heavy metal contamination. Br Med Bull 68:167–182

    PubMed  Article  Google Scholar 

  25. AK (2008) Mode of action and toxicity of trace elements. In: Trace elements as contaminants and nutrients. John Wiley & Sons, Inc., pp 523-553. doi:10.1002/9780470370124.ch21

  26. Brocato J, Costa M (2013) Basic mechanics of DNA methylation and the unique landscape of the DNA methylome in metal-induced carcinogenesis. Crit Rev Toxicol 43(6):493–514

    CAS  PubMed  Article  Google Scholar 

  27. Mosmann T (1983) Rapid colorimetric assay for cellular growth and survival: application to proliferation and cytotosxicity assays. J Immunol Methods 65(1–2):55–63

    CAS  PubMed  Article  Google Scholar 

  28. Ostertag EM, Prak ET, DeBerardinis RJ, Moran JV, Kazazian HH Jr (2000) Determination of L1 retrotransposition kinetics in cultured cells. Nucleic Acids Res 28(6):1418–1423

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  29. Garcia-Perez JL, Morell M, Scheys JO, Kulpa DA, Morell S, Carter CC, Hammer GD, Collins KL, O’Shea KS, Menendez P, Moran JV (2010) Epigenetic silencing of engineered L1 retrotransposition events in human embryonic carcinoma cells. Nature 466(7307):769–773

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  30. Garcia-Perez JL, Marchetto MC, Muotri AR, Coufal NG, Gage FH, O’Shea KS, Moran JV (2007) LINE-1 retrotransposition in human embryonic stem cells. Hum Mol Genet 16(13):1569–1577

    CAS  PubMed  Article  Google Scholar 

  31. Baillie JK, Barnett MW, Upton KR, Gerhardt DJ, Richmond TA, De Sapio F, Brennan PM, Rizzu P, Smith S, Fell M, Talbot RT, Gustincich S, Freeman TC, Mattick JS, Hume DA, Heutink P, Carninci P, Jeddeloh JA, Faulkner GJ (2011) Somatic retrotransposition alters the genetic landscape of the human brain. Nature 479(7374):534–537

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  32. Thomas CA, Paquola AC, Muotri AR (2012) LINE-1 retrotransposition in the nervous system. Annu Rev Cell Dev Biol 28:555–573

    CAS  PubMed  Article  Google Scholar 

  33. Carreira PE, Richardson SR, Faulkner GJ (2014) L1 retrotransposons, cancer stem cells and oncogenesis. FEBS J 281(1):63–73

    CAS  PubMed  Article  Google Scholar 

  34. Lee E, Iskow R, Yang L, Gokcumen O, Haseley P, Luquette LJ 3rd, Lohr JG, Harris CC, Ding L, Wilson RK, Wheeler DA, Gibbs RA, Kucherlapati R, Lee C, Kharchenko PV, Park PJ (2012) Landscape of somatic retrotransposition in human cancers. Science (New York, NY) 337(6097):967–971

    CAS  Article  Google Scholar 

  35. Schneider AM, Duffield AS, Symer DE, Burns KH (2009) Roles of retrotransposons in benign and malignant hematologic disease. Cell Sci 6(2):121–145

    Google Scholar 

  36. Rangwala SH, Kazazian HH Jr (2009) The L1 retrotransposition assay: a retrospective and toolkit. Methods (San Diego, Calif) 49(3):219–226

    CAS  Article  Google Scholar 

  37. ATSDR (2008) Toxicological profile for aluminum. US Department of Health and Human Services, Public Health Service Agency for Toxic Substances and Disease Registry

  38. ATSDR (2007) Toxicological profile for lead. US Department of Health and Human Services, Public Health Service Agency for Toxic Substances and Disease Registry

  39. Wright RO, Schwartz J, Wright RJ, Bollati V, Tarantini L, Park SK, Hu H, Sparrow D, Vokonas P, Baccarelli A (2010) Biomarkers of lead exposure and DNA methylation within retrotransposons. Environ Health Perspect 118(6):790–795

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  40. Wallace NA, Belancio VP, Deininger PL (2008) L1 mobile element expression causes multiple types of toxicity. Gene 419(1–2):75–81. doi:10.1016/j.gene.2008.04.013

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  41. Armendariz AD, Gonzalez M, Loguinov AV, Vulpe CD (2004) Gene expression profiling in chronic copper overload reveals upregulation of Prnp and App. Physiol Genomics 20(1):45–54

    CAS  PubMed  Article  Google Scholar 

  42. ATSDR (2004) Toxicological profile for copper. US Department of Health and Human Services, Public Health Service Agency for Toxic Substances and Disease Registry

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Acknowledgments

The authors thank Tehran University of Medical Sciences for financial support of this project (Grant number. 17245). This study was conducted in the Cellular and Molecular Research Center (CMRC) of Iran University of Medical Sciences as part of a PhD dissertation. Our special thanks are extended to the staff of CMRC for their technical support. The authors would also like to acknowledge with much appreciation the crucial role of Mr. Mohammad Yahya Karimi in Razi Drug Research Center, who was abundantly helpful and offered invaluable assistance and guidance.

Conflict of Interest

No competing financial interests exist.

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Affiliations

  1. Department of Molecular Medicine, Faculty of Advanced Technologies in Medicine (FATiM), Iran University of Medical Sciences, Tehran, Iran

    Abbas Karimi & Zahra Madjd

  2. Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran

    Abbas Karimi & Zahra Madjd

  3. Oncopathology Research Centre, Iran University of Medical Sciences, Tehran, Iran

    Zahra Madjd

  4. Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Poursina St., Tehran, Iran

    Laleh Habibi & Seyed Mohammad Akrami

Authors
  1. Abbas Karimi
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  2. Zahra Madjd
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  3. Laleh Habibi
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  4. Seyed Mohammad Akrami
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Correspondence to Zahra Madjd or Seyed Mohammad Akrami.

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Karimi, A., Madjd, Z., Habibi, L. et al. Evaluating the Extent of LINE-1 Mobility Following Exposure to Heavy Metals in HepG2 Cells. Biol Trace Elem Res 160, 143–151 (2014). https://doi.org/10.1007/s12011-014-0015-7

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  • DOI: https://doi.org/10.1007/s12011-014-0015-7

Keywords

  • Retrotransposition
  • Heavy metals
  • Cytotoxicity
  • LINE-1
  • Human hepatocellular carcinoma cell