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Radiation and Environmental Biophysics

, Volume 40, Issue 2, pp 137–143 | Cite as

Caffeine-inhibitable control of the radiation-induced G2 arrest in L5178Y-S cells deficient in non-homologous end-joining

  • I. Szumiel
  • M. Kapiszewska
  • A. John
  • I. Grądzka
  • D. Kowalczyk
  • P. Janik
Original Paper

Abstract 

The two L5178Y (LY) sublines bear a heterozygous Tp53 mutation that affects its transactivation function. LY-S (radiation-sensitive) cells are deficient in double strand break (DSB) repair by non-homologous end-joining (NHEJ) and do not express p21WAF1 (Cdkna1) either constitutively or after x-irradiation, in contrast to their radiation-resistant counterpart LY-R cells, which express p21WAF1 constitutively. Radiation-induced G2 arrest in LY-S cells is very long (11 h/Gy) but 2 mM caffeine treatment shortens it, decreases the fraction of G2 cells and increases the fraction of apoptotic cells. The treatment also increases the DNA damage that is estimated with the comet assay 18 h after irradiation with 5 Gy (ca. 23% of the initial value for x-rays and ca. 47% for x-rays plus caffeine). This indicates that either the repair has not been completed or the apoptotic DNA fragmentation has been initiated (or both). The same treatment applied to x-irradiated (5 Gy) LY-R cells (G2 arrest, 4 h/Gy) has no radiosensitising effect, induces no apoptosis and does not alter the amount of DNA damage left unrepaired (ca. 28%). The results are compatible with the assumption that inhibition of the Atm-dependent homologous recombination repair by caffeine, brings differential effects in LY sublines because of the defect of the alternative DNA repair system (NHEJ) in LY-S cells.

Keywords

Caffeine Comet Assay Double Strand Break Tp53 Mutation Recombination Repair 
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.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2001

Authors and Affiliations

  • I. Szumiel
    • 1
  • M. Kapiszewska
    • 2
  • A. John
    • 3
  • I. Grądzka
    • 1
  • D. Kowalczyk
    • 4
  • P. Janik
    • 4
  1. 1.Department of Radiobiology and Health Protection, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-918 Warsaw, Poland e-mail: izasz@orange.ichtj.waw.pl Tel.: +48-22-8110736, Fax: +48-22-8111532PL
  2. 2.Department of Biophysics, Institute of Molecular Biology, Jagellonian University, Cracow, PolandPL
  3. 3.Department of Biochemistry, University of Al-Ain, United Arab EmiratesAE
  4. 4.Department of Cell Biology, Oncology Center, Warsaw, PolandPL

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