title: p53 Ser15 phosphorylation disrupts the p53-RPA70 complex and induces RPA70-mediated DNA repair in hypoxia.
abstract: Cellular stressors are known to inhibit the p53-RPA70 (replication protein A, 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(Ser15) phosphorylation, 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 enhancing NER/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.
authors.affiliation: Transcription and Human Biology Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, India.
authors.forename: Esha
authors.initials: E
authors.lastname: Madan
authors.forename: Rajan
authors.initials: R
authors.lastname: Gogna
authors.forename: Uttam
authors.initials: U
authors.lastname: Pati
mesh_terms: D015687:Cell Hypoxia / Q000235:genetics*; D045744:Cell Line, Tumor; D004260:DNA Repair; D006801:Humans; D010766:Phosphorylation; D011485:Protein Binding; D051716:Replication Protein A / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000378:metabolism*
chemical_list: C497167:RPA1 protein, human; D051716:Replication Protein A; D016159:Tumor Suppressor Protein p53; D012694:Serine