# Mechanistic Studies of Type II Topoisomerases and Topoisomerase-Targeted Agents > **NIH NIH R01** · VANDERBILT UNIVERSITY · 2022 · $355,756 ## Abstract Type II topoisomerases are ubiquitous enzymes that are required for proper chromosome structure and segregation and play important roles in DNA replication, transcription, and recombination. These enzymes relax DNA and remove knots and tangles from the genetic material by passing an intact double helix (transport segment) through a transient double-stranded break that they generate in a separate DNA segment (gate segment). Humans encode two closely related isoforms of the type II enzyme, topoisomerase IIα and topoisomerase IIβ. Topoisomerase IIα is essential for the survival of proliferating cells and topoisomerase IIβ plays critical roles during development. However, because these enzymes generate requisite double-stranded DNA breaks during their crucial catalytic functions, they assume a dual persona. Although essential to cell survival, they also pose an intrinsic threat to genomic integrity every time they act. Beyond their critical physiological functions, topoisomerase IIα and IIβ are the primary targets for some of the most active and widely prescribed drugs currently used for the treatment of human cancers. These agents kill cells by stabilizing covalent topoisomerase II-cleaved DNA complexes (cleavage complexes) that are normal, but fleeting, intermediates in the catalytic DNA strand passage reaction. When the resulting enzyme- associated DNA breaks are present in sufficient concentrations, they can trigger cell death pathways. Anticancer drugs that target type II enzymes are referred to as topoisomerase II poisons because they convert these indispensable enzymes to potent physiological toxins that generate DNA damage in treated cells. Although topoisomerase IIα and IIβ are important targets for cancer chemotherapy, they also have the potential to trigger specific leukemias. For example, a small percentage of patients with cancer or multiple sclerosis who are treated with the topoisomerase II-targeted drug mitoxantrone go on to develop acute promyelocytic leukemias (APLs) with 15:17 translocations. Despite the importance of type II topoisomerases in cell growth and cancer, we still have much to learn about how the human enzymes function and interact with DNA and anticancer drugs. Thus, this proposal will further define the catalytic mechanism of type II topoisomerases and examine how enzyme activity is regulated in the cell. It also will define mechanisms by which established and novel topoisomerase II-targeted agents, environ- mental chemicals, and natural products increase levels of enzyme-mediated DNA breaks or inhibit enzyme activity and determine the cellular consequences of topoisomerase II poisons. The primary research models for this study will be human topoisomerase IIα and IIβ, cultured human cells, and Xenopus laevis egg extracts. Gyrase and topoisomerase IV from Escherichia coli and Bacillus anthracis will be used as counterpoints to mechanistic experiments and Mycobacterium tuberculosis gyrase will be used to assess relati... ## Key facts - **NIH application ID:** 10364870 - **Project number:** 2R01GM126363-05 - **Recipient organization:** VANDERBILT UNIVERSITY - **Principal Investigator:** NEIL OSHEROFF - **Activity code:** R01 (R01, R21, SBIR, etc.) - **Funding institute:** NIH - **Fiscal year:** 2022 - **Award amount:** $355,756 - **Award type:** 2 - **Project period:** 2018-02-01 → 2025-11-30 ## Primary source NIH RePORTER: https://reporter.nih.gov/project-details/10364870 ## Citation > US National Institutes of Health, RePORTER application 10364870, Mechanistic Studies of Type II Topoisomerases and Topoisomerase-Targeted Agents (2R01GM126363-05). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10364870. Licensed CC0. --- *[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*