title: Physical and functional interactions between human mitochondrial single-stranded DNA-binding protein and tumour suppressor p53.
abstract: Single-stranded DNA-binding proteins (SSB) form a class of proteins that bind preferentially single-stranded DNA with high affinity. They are involved in DNA metabolism in all organisms and serve a vital role in replication, recombination and repair of DNA. In this report, we identify human mitochondrial SSB (HmtSSB) as a novel protein-binding partner of tumour suppressor p53, in mitochondria. It binds to the transactivation domain (residues 1-61) of p53 via an extended binding interface, with dissociation constant of 12.7 (+/- 0.7) microM. Unlike most binding partners reported to date, HmtSSB interacts with both TAD1 (residues 1-40) and TAD2 (residues 41-61) subdomains of p53. HmtSSB enhances intrinsic 3'-5' exonuclease activity of p53, particularly in hydrolysing 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) present at 3'-end of DNA. Taken together, our data suggest that p53 is involved in DNA repair within mitochondria during oxidative stress. In addition, we characterize HmtSSB binding to ssDNA and p53 N-terminal domain using various biophysical measurements and we propose binding models for both.
authors.affiliation: Centre for Protein Engineering, Medical Research Council, Hills Road, Cambridge CB2 0QH, UK.
authors.forename: Tuck Seng
authors.initials: TS
authors.lastname: Wong
authors.forename: Sridharan
authors.initials: S
authors.lastname: Rajagopalan
authors.forename: Fiona M
authors.initials: FM
authors.lastname: Townsley
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Freund
authors.forename: Miriana
authors.initials: M
authors.lastname: Petrovich
authors.forename: David
authors.initials: D
authors.lastname: Loakes
authors.forename: Alan R
authors.initials: AR
authors.lastname: Fersht
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D001665:Binding Sites; D045744:Cell Line, Tumor; D000074002:DNA Polymerase gamma; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000378:metabolism; D006801:Humans; D024101:Mitochondrial Proteins / Q000378:metabolism*; D011485:Protein Binding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D013696:Temperature; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; D016159:Tumor Suppressor Protein p53; D000080242:8-Hydroxy-2'-Deoxyguanosine; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; D005090:Exodeoxyribonucleases; D003849:Deoxyguanosine