The impact of the human DNA topoisomerase II C-terminal domain on activity.

Background: Type II DNA topoisomerases (topos) are essential enzymes needed for the resolution of topological problems that occur during DNA metabolic processes. Topos carry out an ATP-dependent strand passage reaction whereby one double helix is passed through a transient break in another. Humans have two topoII isoforms, alpha and beta, which while enzymatically similar are differentially expressed and regulated, and are thought to have different cellular roles.

Specific adducts recognised by a monoclonal antibody against cisplatin-modified DNA.

Numerous clinical or experimental studies have employed monoclonal antibody CP9/19 for quantification of cisplatin DNA adducts. The nature of adducts recognised by CP9/19 on polymeric DNA were defined using synthetic deoxynucleotides reacted with cisplatin. Total adduct levels were determined by atomic absorption spectrometry.

Schedule-dependent response of neuroblastoma cell lines to combinations of etoposide and cisplatin.

The growth inhibitory effects of cisplatin and etoposide on neuroblastoma cell lines were investigated in several scheduled combinations. Results were analyzed using median effect and combination index analyses. In all schedules in which cisplatin was administered prior to etoposide a synergistic effect was observed.

Mutagenesis of E477 or K505 in the B' domain of human topoisomerase II beta increases the requirement for magnesium ions during strand passage.

A type II topoisomerase is essential for decatenating DNA replication products, and it accomplishes this task by passing one DNA duplex through a transient break in a second duplex. The B' domain of topoisomerase II contains three highly conserved motifs, EGDSA, PL(R/K)GK(I/L/M)LNVR, and IMTD(Q/A)DXD. We have investigated these motifs in topoisomerase II beta by mutagenesis, and report that they play a critical role in establishing the DNA cleavage-religation equilibrium.