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Loss of Hus1 sensitizes cells to etoposide-induced apoptosis by regulating BH3-only proteins

Oncogene volume 27, pages 7248–7259 (2008)Cite this article

Abstract

The Rad9–Rad1–Hus1 (9-1-1) cell cycle checkpoint complex plays a key role in the DNA damage response. Cells with a defective 9-1-1 complex have been shown to be sensitive to apoptosis induced by certain types of genotoxic stress. However, the mechanism linking the loss of a functional 9-1-1 complex to the cell death machinery has yet to be determined. Here, we report that etoposide treatment dramatically upregulates the BH3-only proteins, Bim and Puma, in Hus1-deficient cells. Inhibition of either Bim or Puma expression in Hus1-knockout cells confers significant resistance to etoposide-induced apoptosis, whereas knockdown of both proteins results in further resistance, suggesting that Bim and Puma cooperate in sensitizing Hus1-deficient cells to etoposide treatment. Moreover, we found that Rad9 collaborates with Bim and Puma to sensitize Hus1-deficient cells to etoposide-induced apoptosis. In response to DNA damage, Rad9 localizes to chromatin in Hus1-wild-type cells, whereas in Hus1-deficient cells, it is predominantly located in the cytoplasm where it binds to Bcl-2. Taken together, these results suggest that loss of Hus1 sensitizes cells to etoposide-induced apoptosis not only by inducing Bim and Puma expressions but also by releasing Rad9 into the cytosol to augment mitochondrial apoptosis.

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Acknowledgements

We thank the Analytical Microscopy Core facility at the H Lee Moffitt Cancer Center and Research Institute for their technical assistance. This work was supported by grants from the National Institutes of Health (CA90315 to H-GW and CA108773 to RSW) and the Department of Defense Breast Cancer Research Program (BC050563 to CLM).

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Authors and Affiliations

  1. Drug Discovery Program, H Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA

    C L Meyerkord, Y Takahashi, R Araya, N Takada & H-G Wang

  2. Cancer Biology PhD Program, H Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, FL, USA

    C L Meyerkord & H-G Wang

  3. Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA

    R S Weiss

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  1. C L Meyerkord
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Correspondence to H-G Wang.

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Supplementary Information accompanies the paper on the Oncogene website (http://www.nature.com/onc)

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Meyerkord, C., Takahashi, Y., Araya, R. et al. Loss of Hus1 sensitizes cells to etoposide-induced apoptosis by regulating BH3-only proteins. Oncogene 27, 7248–7259 (2008). https://doi.org/10.1038/onc.2008.336

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