Cdk5 activator-binding protein C53 regulates apoptosis induced by genotoxic stress via modulating the G2/M DNA damage checkpoint

Hai Jiang, Shouqing Luo, Honglin Li

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


In response to DNA damage, the cellular decision of life versus death involves an intricate network of multiple factors that play critical roles in regulation of DNA repair, cell cycle, and cell death. DNA damage checkpoint proteins are crucial for maintaining DNA integrity and normal cellular functions, but they may also reduce the effectiveness of cancer treatment. Here we report the involvement of Cdk5 activator p35-binding protein C53 in regulation of apoptosis induced by genotoxic stress through modulating Cdkl-cyclin Bl function. C53 was originally identified as a Cdk5 activator p35-binding protein and a caspase substrate. Importantly, our results demonstrated that C53 deficiency conferred partial resistance to genotoxic agents such as etoposide and x-ray irradiation, whereas ectopic expression of C53 rendered cells susceptible to multiple genotoxins that usually trigger G2/M arrest. Furthermore, we found that Cdk1 activity was required for etoposide-induced apoptosis of HeLa cells. Overexpression of C53 promoted Cdk1 activity and nuclear accumulation of cyclin B1, whereas C53 deficiency led to more cytoplasmic retention of cyclin B1, suggesting that C53 acts as a pivotal player in modulating the G2/M DNA damage checkpoint. Finally, C53 and cyclin B1 co-localize and associate in vivo, indicating a direct role of C53 in regulating the Cdk1-cyclin B1 complex. Taken together, our results strongly indicate that in response to genotoxic stress, C53 serves as an important regulatory component of the G2/M DNA damage checkpoint. By overriding the G2/M checkpoint-mediated inhibition of Cdk1-cyclin B1 function, ectopic expression of C53 may represent a novel approach for chemo- and radio-sensitization of cancer cells.

Original languageEnglish (US)
Pages (from-to)20651-20659
Number of pages9
JournalJournal of Biological Chemistry
Issue number21
StatePublished - May 27 2005
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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