Protective role of Puralpha to cisplatin.

BACKGROUND: The nucleic acid-binding protein Puralpha is involved at stalled DNA replication forks, in double-strand break (DSB) DNA repair and the cellular response to DNA replication stress. Puralpha also regulates homologous recombination-directed DNA repair (HRR). RESULTS: Cells lacking Puralpha showed enhanced sensitivity to cisplatin as evaluated by assays for cell viability and cell clonogenicity. This was seen both in Puralpha-negative MEFs and in human glioblastoma cells treated with siRNA directed against Puralpha. MEFs lacking Puralpha also showed enhanced H2AX phosphorylation in response to cisplatin. Repair of a reporter plasmid that had been treated with cisplatin was decreased in a reactivation assay using Puralpha-negative MEFs and the capacity of nuclear extracts from Puralpha-negative MEFs to perform non-homologous end-joining in vitro was also impaired. METHODS: We investigated the effects of the DNA damage-inducing cancer chemotherapeutic agent cisplatin on mouse embryo fibroblasts (MEFs) from PURA(-/-) knockout mice that lack Puralpha. CONCLUSIONS: Puralpha has a role in the cellular response to cisplatin-induced DNA damage and may provide new therapeutic modalities for cisplatin-resistant tumors.