title: Terminal deoxynucleotidyl transferase indiscriminately incorporates ribonucleotides and deoxyribonucleotides.
abstract: Terminal deoxynucleotidyl transferase (TdT) catalyzes the condensation of deoxyribonucleotides on 3'-hydroxyl ends of DNA strands in a template-independent manner and adds N-regions to gene segment junctions during V(D)J recombination. Although TdT is able to incorporate a few ribonucleotides in vitro, TdT discrimination between ribo- and deoxyribonucleotides has never been studied. We found that TdT shows only a minor preference for incorporation of deoxyribonucleotides over ribonucleotides on DNA strands. However, incorporation of ribonucleotides alone or in the presence of deoxyribonucleotides generally leads to premature chain termination, reflecting an impeded accommodation of ribo- or mixed ribo/deoxyribonucleic acid substrates by TdT. An essential catalytic aspartate in TdT was identified, which is a first step toward understanding the apparent lack of sugar discrimination by TdT.
authors.affiliation: Unité de Génétique et Biochimie du Développement, URA CNRS 1960, Institut Pasteur, 25 rue du Dr Roux, 75015 Paris, France.
authors.forename: J B
authors.initials: JB
authors.lastname: Boulé
authors.forename: F
authors.initials: F
authors.lastname: Rougeon
authors.forename: C
authors.initials: C
authors.lastname: Papanicolaou
mesh_terms: D002384:Catalysis; D004253:DNA Nucleotidylexotransferase / Q000502:physiology*; D003854:Deoxyribonucleotides / Q000378:metabolism*; D011995:Recombination, Genetic; D012265:Ribonucleotides / Q000378:metabolism*
chemical_list: D003854:Deoxyribonucleotides; D012265:Ribonucleotides; D004253:DNA Nucleotidylexotransferase