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Radiation and Environmental Biophysics

, Volume 48, Issue 2, pp 205–213 | Cite as

Induced expression of the IER5 gene by γ-ray irradiation and its involvement in cell cycle checkpoint control and survival

  • Ku-Ke Ding
  • Zeng-Fu Shang
  • Chuan Hao
  • Qin-Zhi Xu
  • Jing-Jing Shen
  • Chuan-Jie Yang
  • Yue-Hua Xie
  • Cha Qiao
  • Yu Wang
  • Li-Li Xu
  • Ping-Kun ZhouEmail author
Original Paper

Abstract

The immediate-early response gene 5 (IER5) was previously shown, using microarray analysis, to be upregulated by ionizing radiation. Here we further characterized the dose- and time-dependency of radiation-induced expression of IER5 at doses from 0.5 to 15 Gy by quantitative real-time PCR analyses in HeLa cells and human lymphoblastoid AHH-1 cells. A radiation-induced increase in the IER5 mRNA level was evident 2 h after irradiation with 2 Gy in both cell lines. In AHH-1 cells the expression reached a peak at 4 h and then quickly returned to the control level, while in HeLa cells the expression only remained increased for a short period of time at around 2 h after irradiation before returning to the control. After high-dose irradiation (10 Gy), the induction of the IER5 expression was lower and delayed in AHH-1 cells as compared with 2-Gy irradiated cells. In HeLa cells, at this dose, two peaks of increased expression were observed 2 h and 12–24 h post-irradiation, respectively. RNA interference technology was employed to silence the IER5 gene in HeLa cells. siRNA-mediated suppression of IER5 resulted in an increased proliferation of HeLa cells. Cell growth and survival analyses demonstrated that suppression of IER5 significantly increased the radioresistance of HeLa cells to radiation doses of up to 6 Gy, but barely affected the sensitivity of cells at 8 Gy. Moreover, suppression of IER5 potentiated radiation-induced arrest at the G2-M transition and led to an increase in the fraction of S phase cells. Taken together, we propose that the early radiation-induced expression of IER5 affects the radiosensitivity via disturbing radiation-induced cell cycle checkpoints.

Keywords

HeLa Cell Cell Cycle Checkpoint Clonogenic Survival Assay Flow Cytometry Immunofluorescence Primary Human Fibroblast Cell 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

This work was supported by grants from the National Basic Research Program of MOST, China (973 Program, Grant No: 2007CB914603), the National Natural Science Foundation of China (Grant No: 30371232, No.:30770533), and the Beijing Municipal Education Commission (Science and Technology for Development Program: Km200710025007).

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Ku-Ke Ding
    • 1
  • Zeng-Fu Shang
    • 2
  • Chuan Hao
    • 2
    • 3
  • Qin-Zhi Xu
    • 2
  • Jing-Jing Shen
    • 1
  • Chuan-Jie Yang
    • 3
  • Yue-Hua Xie
    • 2
  • Cha Qiao
    • 2
    • 3
  • Yu Wang
    • 2
  • Li-Li Xu
    • 1
  • Ping-Kun Zhou
    • 2
    Email author
  1. 1.Biomedical Engineering SchoolCapital Medical UniversityBeijingPeople’s Republic of China
  2. 2.Department of Radiation Toxicology and OncologyBeijing Institute of Radiation MedicineBeijingPeople’s Republic of China
  3. 3.The Second HospitalHebei Medical UniversityShijiazhuang CityPeople’s Republic of China

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