Mechanistic studies of amsacrine-resistant derivatives of DNA topoisomerase II. Implications in resistance to multiple antitumor drugs targeting the enzyme.

摘要: Wild-type yeast DNA topoisomerase II and three of its amsacrine-resistant derivatives L475A/L480P, L475A/R476G, A642G, named according to amino acid changes at the codons specified, were overexpressed purified. Because cells expressing several mutant enzymes missing portions carboxyl-terminal domain wild-type enzyme previously found exhibit amsacrine resistance, a truncation protein Top2(1-1166), which lacks last 263 acids enzyme, was also These purified used in measurement turnover numbers DNA-dependent hydrolysis ATP, transport one segment through another, effects amsacrine, teniposide or Ca(II) on formation enzyme-DNA covalent intermediate. The results these studies indicate that mutations leading cellular resistance may occur by different mechanisms, including reduction nuclear concentration attenuation intrinsic catalytic steps enzyme. significance this underpinning mechanistic diversity drug relation simultaneous development chemically distinct drugs target are discussed.