p53 Ser 15 phosphorylation disrupts the p53-RPA70 complex and induces RPA70-mediated DNA repair in hypoxia

Esha Madan, Rajan Gogna, Uttam Pati

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Abstract

Cellular stressors are known to inhibit the p53-RPA70 (replication proteinA, 70 kDa subunit) complex, and RPA70 increases cellular DNA repair in cancer cells. We hypothesized that regulation of RPA70-mediated DNA repair might be responsible for the inhibition of apoptosis in hypoxic tumours. We have shown that, in cancer cells, hypoxia disrupts the p53-RPA70 complex, thereby enhancing RPA70-mediated NER (nucleotide excision repair)/NHEJ (non-homologous end-joining) repair. In normal cells,RPA70 binds to the p53-NTD (N-terminal domain),whereas this binding is disrupted in hypoxia. Phosphorylation of p53-NTD is a crucial event in dissociating both NTD-RPA70 and p53-RPA70 complexes. Serial mutations at serine and threonine residues in the NTD confirm that p53 Ser15 phosphorylation induces dissociation of the p53-RPA70 complex in hypoxia. DNA-PK (DNA-dependent protein kinase) is shown to induce p53 Ser15phosphorylation, thus enhancing RPA70-mediated NER/NHEJ repair. Furthermore, RPA70 gene silencing induces significant increases in cellular apoptosis in the resistant hypoxic cancer cells. We have thus elucidated a novel pathway showing how DNA-PK-mediated p53 Ser15 phosphorylation dissociates the p53-RPA70 complex, thus enhancingNER/NHEJ repair, which causes resistance to apoptosis in hypoxic cancer cells. This novel finding may open new strategies in developing cancer therapeutics on the basis of the regulation of RPA70-mediated NER/NHEJ repair.

Original languageEnglish (US)
Pages (from-to)811-820
Number of pages10
JournalBiochemical Journal
Volume443
Issue number3
DOIs
StatePublished - May 1 2012

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All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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