p53 enhances the fidelity of DNA synthesis by human immunodeficiency virus type 1 reverse transcriptase

M. Bakhanashvili

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


The tumor suppressor protein p53 plays a critical role in the maintenance of genetic integrity. p53 possesses 3′→5′ exonuclease activity, however, the significance of this function in DNA replication process remains elusive. It was suggested that 3′→5′ exonuclease activity of p53 may provide a proofreading function for DNA polymerases. In order to better understand the significance of this activity, the purified wild-type recombinant p53 was further evaluated for substrate specificity and for contribution to the accuracy of DNA synthesis. p53-associated 3′→5′ exonuclease displays 3′ terminal nucleotide excision from RNA/DNA template-primer using ribosomal RNA as a template. The data demonstrate that p53 is highly efficient in removing a terminal mispair. Analysis of mispair excision opposite the template adenine residue shows that p53 catalyzes 3′ terminal mismatch excision with a specificity of A:G > A:A > A:C. Hence, the observed specificity of mismatch excision indicates that p53 exonucleolytic proofreading preferentially repairs transversion mutations. The influence of the p53 on the accuracy of DNA synthesis was determined with exonuclease-deficient human immunodeficiency virus-1 (HIV-1) reverse transcriptase (RT), a key enzyme in the life cycle of the virus, that contributes significantly to the low accuracy of proviral DNA synthesis. Using an in vitro biochemical assay with recombinant purified HIV-1 RT, p53 and defined RNA/DNA or DNA/DNA template-primers, two basic features related to fidelity of DNA synthesis were studied: the misinsertion and mispair extension. The misincorporation of non-complementary deoxynucleotides into nascent DNA and subsequent mispair extension by HIV-1 RT were substantially decreased in the presence of p53 with both RNA/DNA and DNA/DNA template-primers. In addition, the productive interaction between polymerization (by HIV-1 RT) and exonuclease (by p53) activities was observed; p53 preferentially hydrolyzes mispaired 3′-termini, permitting subsequent extension of the correctly paired 3′-terminus by HIV-1 RT. Taken together the data demonstrate that preferential excision of mismatched nucleotides by 3′→5′ exonuclease activity of wild-type p53 enhances the fidelity of DNA synthesis by HIV-1 RT in vitro, thus providing a biochemical mechanism to reduce mutations caused by incorporation of mismatched nucleotides. The fact that p53 is reactive with both RNA/DNA and DNA/DNA template-primers raises an interesting possibility of the existence of functional cooperation between p53 and HIV-1 RT in cytoplasm during the reverse transcription process, which may be important for maintaining HIV genomic integrity.

Original languageEnglish
Pages (from-to)7635-7644
Number of pages10
Issue number52
StatePublished - 15 Nov 2001
Externally publishedYes

Bibliographical note

Funding Information:
The author is indebted to Prof M Oren (from Weizmann Institute, Rehovot, Israel) for the supply of purified P53 protein and Prof A Hizi (from Tel-Aviv University, Tel-Aviv, Israel) for supply of purified HIV-1 RT. The author thanks Prof E Rubinstein, Prof Y Sidi and Dr G Lilling for critically reading the manuscript. This research was supported by a grant from Israel Cancer Research Fund (ICRF) and by a grant from Israel Cancer Association (20000062 – B).


  • 3′→5′ exonuclease
  • DNA replication fidelity
  • HIV-1 RT
  • p53


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