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N-terminal and core-domain random mutations in human topoisomerase II alpha conferring bisdioxopiperazine resistance

L H Jensen1, I Wessel, M Møller

  • 1Department of Pathology, Laboratory Center, Righospitalet, Copenhagen, Denmark. lhjensen@rh.dk

FEBS Letters
|October 18, 2000
PubMed

Insights

Mutations in human topoisomerase II alpha can confer resistance to bisdioxopiperazine compounds like ICRF-187. These mutations affect drug response through different mechanisms, highlighting distinct protein domains involved.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Genetics

Background:

  • Human topoisomerase II alpha is a crucial enzyme for DNA replication and repair.
  • Bisdioxopiperazine compounds, such as ICRF-187, are known inhibitors of topoisomerase II.
  • Understanding drug resistance mechanisms is vital for developing effective cancer therapies.

Purpose of the Study:

  • To identify mutations in human topoisomerase II alpha that confer resistance to ICRF-187.
  • To investigate the mechanisms underlying cellular bisdioxopiperazine resistance.
  • To explore the role of different protein domains in drug response.

Main Methods:

  • Random mutagenesis of human topoisomerase II alpha cDNA.
  • Functional expression in yeast cells lacking endogenous topoisomerase II activity.
  • Clonogenic assays to measure cellular resistance to ICRF-187.
  • In vitro assays with purified recombinant mutant proteins to assess catalytic inhibition.

Main Results:

  • Five functional mutations (L169F, G551S, P592L, D645N, T996L) conferring significant ICRF-187 resistance were identified.
  • The L169F mutation resulted in a protein highly resistant to ICRF-187 inhibition in vitro.
  • Mutations G551S, D645N, and T996L conferred cellular resistance without affecting in vitro catalytic sensitivity.
  • Results suggest at least two distinct classes of mutations conferring bisdioxopiperazine resistance.

Conclusions:

  • Cellular resistance to bisdioxopiperazines can arise from mutations that either alter drug interaction or affect other cellular processes.
  • Different domains within topoisomerase II alpha are involved in mediating the response to bisdioxopiperazine compounds.
  • These findings provide insights into drug resistance mechanisms and potential therapeutic strategies targeting topoisomerase II.

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