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J Biochem Mol Toxicol. 2012 Nov;26(11):429-38. doi: 10.1002/jbt.21438. Epub 2012 Sep 12.

TOPORS modulates H2AX discriminating genotoxic stresses.

Author information

  • 1Division of Radiation Effect Research, Radiation Health Research Institute, Korea Hydro & Nuclear Power Co., Ltd., 132-703, Seoul, Korea. bovine@khnp.co.kr


H2AX plays an important role in chromatin reorganization implicated in DNA repair and apoptosis under various DNA damaging conditions. In this study, the interaction between TOPORS (topoisomerase I-binding protein) and H2AX was verified using mammalian cell extracts exposed to diverse DNA damaging stresses such as ionizing radiation, doxorubicin, camptothecin, and hydrogen peroxide. In vitro assays for ubiquitination revealed that TOPORS functions as a novel E3 ligase for H2AX ubiquitination. TOPORS was found to be dissociated from H2AX proteins when cells were exposed to oxidative stress, but not replication-inducing DNA damaging stress. The protein stability of H2AX was decreased when TOPORS was ectopically expressed in cells, and oxidative stresses such as hydrogen peroxide and ionizing radiation induced recovery of the H2AX protein level. Therefore, these biochemical data suggest that TOPORS plays a key role in the turnover of H2AX protein, discriminating the type of DNA damaging stress.

© 2012 Wiley Periodicals, Inc.

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