Mutations of human DNA topoisomerase I at poly(ADP-ribose) binding sites: modulation of camptothecin activity by ADP-ribose polymers

• Published in: Journal of experimental & clinical cancer research Vol. 33; no. 1; p. 71
• Main Authors: Tesauro, Cinzia, Graziani, Grazia, Arnò, Barbara, Zuccaro, Laura, Muzi, Alessia, D'Annessa, Ilda, Santori, Elettra, Tentori, Lucio, Leonetti, Carlo, Fiorani, Paola, Desideri, Alessandro
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 17.09.2014; BioMed Central
• Subjects: Amino Acid Sequence; Amino acids; Analysis; Antineoplastic Agents, Phytogenic - pharmacology; Apoptosis; Binding Sites; Camptothecin - pharmacology; Cancer; Cancer therapies; Clinical trials; Deoxyribonucleic acid; DNA; DNA Topoisomerases, Type I - chemistry; DNA Topoisomerases, Type I - genetics; DNA Topoisomerases, Type I - metabolism; Enzyme Activation; Enzymes; Genetic aspects; Health aspects; Humans; Hydrophobic and Hydrophilic Interactions; Kinetics; Metastasis; Models, Molecular; Molecular Sequence Data; Mutation; Poly Adenosine Diphosphate Ribose - metabolism; Polymers; Protein Binding; Protein Conformation; Protein Interaction Domains and Motifs; Proteins; Studies; Topoisomerase I Inhibitors - pharmacology
• ISSN: 1756-9966; 0392-9078; 1756-9966
• DOI: 10.1186/s13046-014-0071-z

DNA topoisomerases are key enzymes that modulate the topological state of DNA through the breaking and rejoining of DNA strands. Human topoisomerase I belongs to the family of poly(ADP-ribose)-binding proteins and is the target of camptothecin derived anticancer drugs. Poly(ADP-ribosyl)ation occurs at specific sites of the enzyme inhibiting the cleavage and enhancing the religation steps during the catalytic cycle. Thus, ADP-ribose polymers antagonize the activity of topoisomerase I poisons, whereas PARP inhibitors increase their antitumor effects. Using site-directed mutagenesis we have analyzed the interaction of human topoisomerase I and poly(ADP-ribose) through enzymatic activity and binding procedures. Mutations of the human topoisomerase I hydrophobic or charged residues, located on the putative polymer binding sites, are not sufficient to abolish or reduce the binding of the poly(ADP-ribose) to the protein. These results suggest either the presence of additional binding sites or that the mutations are not enough perturbative to destroy the poly(ADP-ribose) interaction, although in one mutant they fully abolish the enzyme activity. It can be concluded that mutations at the hydrophobic or charged residues of the putative polymer binding sites do not interfere with the ability of poly(ADP-ribose) to antagonize the antitumor activity of topoisomerase I poisons.