title: Removal of ribonucleotides by p53 protein incorporated during DNA synthesis by HIV-1 reverse transcriptase.
abstract: HIV-1 reverse transcriptase frequently incorporates ribonucleotides into the proviral DNA in macrophages, but not in lymphocytes. The enzyme exerts an efficient ribonucleotide-terminated primer extension capacity. Furthermore, ribonucleotide-editing repair is attenuated in macrophages. Tumor suppressor p53 protein, displaying an intrinsic 3'→5' exonuclease activity, was found to be involved in efficient proofreading of base-base mismatches produced during DNA synthesis. As the presence of proofreading activity is cardinal for the DNA synthesis accuracy, it was of interest to assess whether p53 can serve as a trans-acting proofreader for HIV-1 reverse transcriptase during ribonucleotide incorporation.
  
  
  
  We investigated the potential involvement of cytoplasmic p53 in error correction during insertion of ribonucleotides into DNA by recombinant HIV-1 reverse transcriptase in a p53-proficient and deficient background.
  
  
  
  Primer extension reactions were carried out to elucidate the incorporation and removal of ribonucleotides.
  
  
  
  The biochemical studies suggest that p53 is involved in a ribonucleotide damage-associated repair mechanism through its capacity to remove preformed 3'-terminal ribonucleotides, to decrease ribonucleotide incorporation and to prevent the 3'-ribo-terminated primer extension during ongoing DNA synthesis by HIV-1 reverse transcriptase. A positive correlation exists between the presence of endogenous p53 and decrease in stable incorporation of ribonucleotides into DNA with p53-harboring lysates of HCT116 cells. p53, by preferential removal of purine over pyrimidine ribonucleotides, may affect the ribonucleotide mutation spectra produced by HIV-1 reverse transcriptase.
  
  
  
  The data implies that p53 can excise incorrect sugar in addition to base mispairs, thereby expanding the role of p53 in the repair of nucleic acids replication errors.
authors.affiliation: aInfectious Diseases Unit, Sheba Medical Center, Tel HashomerbDepartment of Cell and Developmental Biology, Sackler School of Medicine, Tel Aviv University, Tel AvivcMina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
authors.forename: Tzofit
authors.initials: T
authors.lastname: Akua
authors.forename: Galia
authors.initials: G
authors.lastname: Rahav
authors.forename: Yossi
authors.initials: Y
authors.lastname: Saragani
authors.forename: Amnon
authors.initials: A
authors.lastname: Hizi
authors.forename: Mary
authors.initials: M
authors.lastname: Bakhanashvili
mesh_terms: D004247:DNA / Q000096:biosynthesis*; D004261:DNA Replication; D054303:HIV Reverse Transcriptase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012265:Ribonucleotides / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D012265:Ribonucleotides; D016159:Tumor Suppressor Protein p53; D004247:DNA; C514824:reverse transcriptase, Human immunodeficiency virus 1; D054303:HIV Reverse Transcriptase