title: Structure of the topoisomerase II ATPase region and its mechanism of inhibition by the chemotherapeutic agent ICRF-187.
abstract: Type IIA topoisomerases both manage the topological state of chromosomal DNA and are the targets of a variety of clinical agents. Bisdioxopiperazines are anticancer agents that associate with ATP-bound eukaryotic topoisomerase II (topo II) and convert the enzyme into an inactive, salt-stable clamp around DNA. To better understand both topo II and bisdioxopiperazine function, we determined the structures of the adenosine 5'-[beta,gamma-imino]-triphosphate-bound yeast topo II ATPase region (ScT2-ATPase) alone and complexed with the bisdioxopiperazine ICRF-187. The drug-free form of the protein is similar in overall fold to the equivalent region of bacterial gyrase but unexpectedly displays significant conformational differences. The ternary drug-bound complex reveals that ICRF-187 acts by an unusual mechanism of inhibition in which the drug does not compete for the ATP-binding pocket, but bridges and stabilizes a transient dimer interface between two ATPase protomers. Our data explain why bisdioxopiperazines target ATP-bound topo II, provide a structural rationale for the effects of certain drug-resistance mutations, and point to regions of bisdioxopiperazines that might be modified to improve or alter drug specificity.
authors.affiliation: Department of Molecular and Cell Biology, 237 Hildebrand Hall, University of California, Berkeley, CA 94720-3206, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Classen
authors.forename: Stephane
authors.initials: S
authors.lastname: Olland
authors.forename: James M
authors.initials: JM
authors.lastname: Berger
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001665:Binding Sites; D004250:DNA Topoisomerases, Type II / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation; D011929:Razoxane / Q000494:pharmacology*; D059005:Topoisomerase II Inhibitors
chemical_list: D000970:Antineoplastic Agents; D059005:Topoisomerase II Inhibitors; D011929:Razoxane; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D004250:DNA Topoisomerases, Type II