Physical and functional interactions between human mitochondrial single-stranded DNA-binding protein and tumour suppressor p53.
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.
Wong
Tuck Seng
TS
Centre for Protein Engineering, Medical Research Council, Hills Road, Cambridge CB2 0QH, UK.
Rajagopalan
Sridharan
S
Townsley
Fiona M
FM
Freund
Stefan M
SM
Petrovich
Miriana
M
Loakes
David
D
Fersht
Alan R
AR
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*
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