title: The HAP1 protein stimulates the turnover of human mismatch-specific thymine-DNA-glycosylase to process 3,N(4)-ethenocytosine residues.
abstract: When present in DNA, 3,N(4)-ethenocytosine (epsilon C) residues are potentially mutagenic and carcinogenic in vivo. The enzymatic activity responsible for the repair of the epsilon C residues in human cells is the hTDG protein, the human thymine-DNA-glycosylase that removes thymine in a T/G base pair [Proc. Natl. Acad. Sci., U.S.A., 95 (1998) 8508]. One of the distinctive properties of the hTDG protein is that it remains tightly bound to the AP-site resulting from its glycosylase activity. In this paper we report that the human AP endonuclease, the HAP1 (Ape1, APEX Ref-1) protein, stimulates the processing of epsilon C residues by the hTDG protein in vitro, in a dose-dependent manner. This property of HAP1 protein is specific since E.coli Fpg, Nfo and Nth proteins, all endowed with an AP nicking activity, do not show similar features. The results suggest that the HAP1 protein displaces the hTDG protein bound to the AP-site and therefore increases the turnover of the hTDG protein. However, using a variety of techniques including gel retardation assay, surface plasmon resonance and two-hybrid system, it was not possible to detect evidence for a complex including the substrate, the hTDG and HAP1 proteins.
authors.affiliation: Groupe Réparation de l'ADN, UMR 8532 CNRS, 39 rue C. Desmoulins, Institut Gustave Roussy, 94805 Villejuif Cedex, France.
authors.forename: C V
authors.initials: CV
authors.lastname: Privezentzev
authors.forename: M
authors.initials: M
authors.lastname: Saparbaev
authors.forename: J
authors.initials: J
authors.lastname: Laval
mesh_terms: D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D019757:Carbon-Oxygen Lyases / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D003596:Cytosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D011088:DNA Ligases / Q000737:chemistry / Q000378:metabolism; D004260:DNA Repair / Q000187:drug effects / Q000502:physiology*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043382:DNA-Formamidopyrimidine Glycosylase; D043224:Deoxyribonuclease (Pyrimidine Dimer); D043223:Deoxyribonuclease IV (Phage T4-Induced); D004305:Dose-Response Relationship, Drug; D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D029968:Escherichia coli Proteins; D006801:Humans; D008274:Magnesium / Q000494:pharmacology; D009699:N-Glycosyl Hydrolases / Q000378:metabolism / Q000494:pharmacology; D009841:Oligonucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D020349:Surface Plasmon Resonance; D020798:Two-Hybrid System Techniques
chemical_list: C018289:3,N(4)-ethenocytosine; D029968:Escherichia coli Proteins; D009841:Oligonucleotides; D003596:Cytosine; D004706:Endodeoxyribonucleases; D043223:Deoxyribonuclease IV (Phage T4-Induced); D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; D019757:Carbon-Oxygen Lyases; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D011088:DNA Ligases; D008274:Magnesium