title: DNA topoisomerases as repair enzymes: mechanism(s) of action and regulation by p53.
abstract: DNA topoisomerases regulate the organization of DNA and are important targets for many clinically used antineoplastic agents. In addition, DNA topoisomerases modulate the cellular sensitivity toward a number of DNA damaging agents. Increased topoisomerase II activities were shown to contribute to the resistance of both nitrogen mustard- and cisplatin-resistant cells. Similarly, cells with decreased topoisomerase II levels show increased sensitivity to cisplatin, carmustine, mitomycin C and nitrogen mustard. Recent studies propose that topoisomerases may be involved in damage recognition and DNA repair at several different levels including: 1) the initial recognition of DNA lesions; 2) DNA recombination; and 3) regulation of DNA structure. The stress-activated oncogene suppressor protein p53 can modulate the activity of at least three different human topoisomerases, either directly by molecular associations or by transcriptional regulation. Since DNA topoisomerases have considerable recombinase activities, inappropriately activated topoisomerases in tumor cells lacking functional p53 may contribute to the genetic instability of these cells.
authors.affiliation: Laboratory of Biology and Pharmacology of DNA Topoisomerases, CNRS UMR 1772, Institut Gustave-Roussy PR2, Villejuif, France. aklarsen@igr.fr
authors.forename: A K
authors.initials: AK
authors.lastname: Larsen
authors.forename: C
authors.initials: C
authors.lastname: Gobert
authors.forename: C
authors.initials: C
authors.lastname: Gilbert
authors.forename: J
authors.initials: J
authors.lastname: Markovits
authors.forename: K
authors.initials: K
authors.lastname: Bojanowski
authors.forename: A
authors.initials: A
authors.lastname: Skladanowski
mesh_terms: D000818:Animals; D006224:Cricetinae; D004247:DNA / Q000235:genetics; D004260:DNA Repair; D004264:DNA Topoisomerases, Type I; D006801:Humans; D011995:Recombination, Genetic; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53
chemical_list: D016159:Tumor Suppressor Protein p53; D004247:DNA; D004264:DNA Topoisomerases, Type I