Abstract
Rev7p has been suggested to play an important role in regulating DNA damage response in yeast, and recently, the human homologue (i.e., MAD2B) has been identified, which shares significant homology to the mitotic checkpoint protein MAD2. In this study, we investigated whether MAD2B played a key role in cellular sensitivity to DNA-damaging anticancer drugs by suppressing its expression using RNA interference in nasopharyngeal carcinoma cells. Using colony formation assay, we found that suppression of MAD2B conferred hypersensitivity to a range of DNA-damaging agents, especially DNA cross-linkers, such as cisplatin, and gamma-irradiation. This effect was associated with reduced frequencies of spontaneous and drug-induced mutations, elevated phosphorylation of histone H2AX, and markedly increased chromosomal aberrations in response to DNA damage. In addition, there was also a significant decrease in cisplatin-induced sister chromatid exchange rate, a marker for homologous recombination-mediated post-replication repair in MAD2B-depleted cells. These results indicate that MAD2B may be a key factor in regulating cellular response to DNA damage in cancer cells. Our findings reveal a novel strategy for cancer therapy, in which cancer cells are sensitized to DNA-damaging anticancer drugs through inactivation of the MAD2B gene.
Highlights
The precise replication of the genome and the maintenance of its integrity are vital for survival and prevention of various diseases, including cancer [1]
The shMAD2B-induced hypersensitivity was associated with reduced spontaneous and DNA damage–induced mutagenesis, defective DNA repair, and subsequent activation of apoptosis, suggesting that similar to its yeast counterpart Rev7p, human MAD2B plays an essential role in DNA damage tolerance in cancer cells
We showed that loss of MAD2B led to reduced rates of spontaneous and cisplatin-induced mutations at the HPRT locus (Fig. 3)
Summary
The precise replication of the genome and the maintenance of its integrity are vital for survival and prevention of various diseases, including cancer [1]. Several lines of evidence suggest that human MAD2B and MAD2 have related functions in regulating mitotic checkpoint and the activity of anaphase-promoting complex In papillary renal cell carcinoma cells, restoration of MAD2B nuclear localization by overexpression of PRCC protein could increase the mitotic checkpoint function in response to nocodazole, a microtubule-disrupting agent [21]. Several independent studies based on yeast two-hybrid technology have shown that MAD2B interacts with other proteins, such as adenovirus death protein, trichosanthin, and metalloprotease disintegrin MDC9 [22,23,24], suggesting that MAD2B might play multiple roles in addition to TLS in the regulation of cell growth
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