title: Loss of Hus1 sensitizes cells to etoposide-induced apoptosis by regulating BH3-only proteins.
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.
authors.affiliation: Drug Discovery Program, H Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Meyerkord
authors.forename: Y
authors.initials: Y
authors.lastname: Takahashi
authors.forename: R
authors.initials: R
authors.lastname: Araya
authors.forename: N
authors.initials: N
authors.lastname: Takada
authors.forename: R S
authors.initials: RS
authors.lastname: Weiss
authors.forename: H-G
authors.initials: HG
authors.lastname: Wang
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics*; D000072224:Bcl-2-Like Protein 11; D018797:Cell Cycle Proteins / Q000235:genetics*; D004249:DNA Damage; D005047:Etoposide / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D018797:Cell Cycle Proteins; C549605:HUS1 protein, human; C462949:HUS1B protein, human; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D005047:Etoposide
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