The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The UniProt accession P11388 corresponds to human DNA topoisomerase 2-alpha (TOP2A; DNA topoisomerase IIα; EC 5.6.2.2), a type IIA topoisomerase that functions as a homodimeric, ATP-dependent nuclear enzyme involved in resolving DNA topological problems during replication and mitosis. Multiple recent reviews explicitly describe the enzyme’s ATP-driven strand-passage mechanism, covalent 5′-phosphotyrosyl DNA intermediate, and mitotic chromosome roles consistent with UniProt P11388 and a type II topoisomerase family member. (zhou2024advancesinresearch pages 2-4, matiasbarrios2023theimplicationof pages 2-4)
DNA topoisomerase IIα (TOP2A) is a type II topoisomerase that changes DNA topology by creating a transient double-strand break (DSB) in one DNA duplex segment and passing a second duplex segment through the break before re-ligating the cut DNA. This enables cells to resolve torsional stress and entanglements that arise during high-throughput DNA transactions. (zhou2024advancesinresearch pages 2-4, matiasbarrios2023theimplicationof pages 2-4)
TOP2A is particularly critical in proliferating cells, with expression and abundance peaking around G2/M, and with strong mitotic chromosome association, matching its primary cellular role in supporting chromosome condensation and segregation. (matiasbarrios2023theimplicationof pages 2-4, zhou2024advancesinresearch pages 2-4)
Core reaction (strand passage / decatenation): TOP2A catalyzes an ATP-dependent duplex DNA strand-passage reaction. Mechanistically, it binds a “gate” DNA segment (G-segment), cleaves both strands, transports a second duplex (T-segment) through the break, and then reseals the G-segment. (zhou2024advancesinresearch pages 2-4, matiasbarrios2023theimplicationof pages 2-4)
Chemical mechanism: A catalytic tyrosine performs a nucleophilic attack on the DNA phosphodiester backbone to form a covalent 5′-phosphotyrosyl TOP2A–DNA intermediate (a reversible cleavage complex) that protects the DNA ends during the cycle. (zhou2024advancesinresearch pages 2-4, matiasbarrios2023theimplicationof pages 2-4)
Energy/cofactors: The full catalytic cycle requires ATP (binding/hydrolysis drives conformational changes and completion of strand passage) and divalent metal ions such as Mg2+ for DNA cleavage chemistry. (matiasbarrios2023theimplicationof pages 2-4, matiasbarrios2023theimplicationof media f3b15698)
A schematic of this catalytic cycle and inhibitor intervention points (poisons versus catalytic inhibitors) is shown in a recent review figure (matiasbarrios2023theimplicationof media f3b15698).
TOP2A does not recognize a narrow DNA sequence substrate in the way many enzymes recognize small molecules. Its “specificity” is functional/structural: it targets topological DNA substrates, including:
- DNA catenanes (interlinked sister chromatids) requiring decatenation during mitosis. (benoit2025investigatingthemitotic pages 21-25, benoit2025investigatingthemitotic pages 25-28)
- Positive and negative supercoils, consistent with its role in resolving torsional stress during replication/transcription and structural maintenance of chromosomes. (benoit2025investigatingthemitotic pages 21-25, matiasbarrios2023theimplicationof pages 2-4)
TOP2A and TOP2B are two human type IIA topoisomerase isoforms with non-redundant biology. In mitosis, TOP2A is emphasized as the major chromosome-associated isoform required for proper chromosome individualization/segregation, while TOP2B is less tightly chromatin-associated in mitosis in the same discussions. (benoit2025investigatingthemitotic pages 25-28)
TOP2A is nuclear and becomes strongly associated with mitotic chromosomes, including enrichment along chromosome axes/scaffold, consistent with a direct role in mitotic chromosome condensation, individualization, and segregation. (matiasbarrios2023theimplicationof pages 2-4, benoit2025investigatingthemitotic pages 25-28)
A mitochondrial role for TOP2 isoforms is not supported in the retrieved evidence: a systematic analysis of human topoisomerase localization/activity found no evidence for TOP2 localization to mitochondria. (benoit2025investigatingthemitotic pages 21-25)
TOP2A is tightly linked to late cell-cycle stages and mitotic progression: it is needed to remove persistent sister-chromatid entanglements to enable faithful chromosome segregation. Its activity is integrated with the decatenation checkpoint, and cellular outcomes after TOP2A inhibition depend on genetic context such as p53 status. (borella2024targetingtop2ain pages 2-4, zhou2024advancesinresearch pages 2-4)
TOP2A contains an N-terminal ATPase region and a central catalytic core (tyrosine-mediated cleavage), and an isoform-specific C-terminal domain (CTD) that contributes to nuclear localization and chromatin tethering, particularly important for mitotic chromosomal binding and sister chromatid separation. (zhou2024advancesinresearch pages 2-4, benoit2025investigatingthemitotic pages 21-25)
Recent review-level synthesis emphasizes that the CTD undergoes diverse post-translational modifications (PTMs) that modulate catalytic activity and protein interactions, supporting a view of TOP2A regulation as a combination of cell-cycle expression control and PTM-tuned chromatin engagement. (zhou2024advancesinresearch pages 2-4)
A 2023 review focused on synthetic-lethal strategies succinctly summarizes a key concept: many clinically used TOP2-targeting chemotherapies are “poisons” that stabilize the normally transient TOP2 cleavage complex, converting a controlled intermediate into persistent DNA damage that triggers cell-cycle arrest and cell death. (matiasbarrios2023theimplicationof pages 2-4, matiasbarrios2023theimplicationof media f3b15698)
A 2024 review focused on TOP2A in malignancy and targeted agents identifies TOP2A as a validated target of commonly used drugs including etoposide and doxorubicin/adriamycin, and distinguishes these poisons from catalytic inhibitors that can inhibit ATPase activity without stabilizing covalent TOP2A–DNA cleavage complexes. (zhou2024advancesinresearch pages 9-11)
Figure evidence: The inhibitor intervention points in the TOP2 catalytic cycle (including etoposide/doxorubicin/amsacrine as poisons) are illustrated in Figure 1 of Matias‑Barrios & Dong (2023). (matiasbarrios2023theimplicationof media f3b15698)
A 2024 review aggregates large-cohort genomic observations: across ~24,000 solid tumors, ~4% show TOP2A amplification; in another cohort of 4,903 tumors, 129 (2.6%) exhibited TOP2A–HER2 co-amplification, with some cancer types showing >40% co-amplification in subsets and up to ~10% of breast tumors exhibiting TOP2A amplification without HER2 amplification in the cited analyses. (zhou2024advancesinresearch pages 1-2)
The same synthesis highlights recurrent TOP2A variants (e.g., p.K743N) associated with a characteristic mutational signature and links specific somatic variants to altered enzyme function and genomic instability. (zhou2024advancesinresearch pages 1-2, zhou2024advancesinresearch pages 2-4)
TOP2A is a central drug target in oncology because proliferating tumor cells are especially dependent on TOP2A function to manage replication/mitotic stress. Clinically used TOP2 poisons (e.g., anthracyclines and etoposide) exploit the cleavage complex mechanism to induce lethal DNA damage. (zhou2024advancesinresearch pages 9-11, matiasbarrios2023theimplicationof media f3b15698)
A major real-world limitation is toxicity driven by TOP2 interference in normal proliferative tissues: the 2024 review notes that TOP2A inhibition can induce DNA DSBs in bone marrow leading to myelosuppression, and TOP2 targeting is associated with therapy-related leukemias in clinical contexts. (zhou2024advancesinresearch pages 9-11)
Because TOP2A expression peaks in dividing cells, TOP2A is commonly treated as a proliferation-associated biomarker. In cholangiocarcinoma, TOP2A immunohistochemical (H-score) stratification was used to define high vs low expressors, and high expression associated with significantly worse survival outcomes. (ong2023prognosticsignificanceof pages 1-2, ong2023prognosticsignificanceof pages 3-5)
In breast cancer endocrine therapy resistance profiling, TOP2A appeared among differentially expressed genes linked to recurrence during endocrine therapy, supporting ongoing use of TOP2A expression in multi-marker recurrence-risk contexts. (ong2023prognosticsignificanceof pages 3-5)
Across recent reviews, a recurring expert interpretation is that TOP2A’s essentiality derives from its ability to solve otherwise intractable topological problems by transiently generating DSBs, but that this same chemistry creates an intrinsic hazard: if the normally reversible cleavage complex is stabilized (by drugs, DNA structures, or mutations), genome instability and cell death can follow. This is the conceptual basis for both anticancer efficacy (poisoning) and adverse outcomes (genotoxicity). (zhou2024advancesinresearch pages 2-4, matiasbarrios2023theimplicationof pages 2-4)
The 2024 malignancy-focused review highlights that TOP2A’s CTD provides key nuclear localization and chromatin tethering functions and is PTM-modulated, aligning with a contemporary view that catalytic core chemistry is not the full story—efficient, properly localized decatenation in mitosis depends on regulated chromatin engagement. (zhou2024advancesinresearch pages 2-4)
Ong et al. (publication date Apr 2023; URL https://doi.org/10.31083/j.fbl2804075) analyzed 182 intrahepatic cholangiocarcinoma (iCCA) cases and reported that high TOP2A expression was significantly associated with worse overall survival, disease-specific survival, and metastasis-free survival (all p < 0.0001 in the available text). (ong2023prognosticsignificanceof pages 1-2, ong2023prognosticsignificanceof pages 3-5)
Wu et al. (publication date May 2024; URL https://doi.org/10.1038/s41598-024-63055-2) report TOP2A is upregulated in NSCLC and functionally promotes migration/invasion and EMT, with mechanistic linkage to Wnt/β-catenin signaling (interaction with Wnt3a and suppression of TOP2A pro-metastatic effects by Wnt3a silencing). The excerpted evidence did not include numerical effect sizes, but the experimental toolkit included qRT-PCR, immunoblotting/IHC, migration/invasion assays, cytoskeletal staining, and apoptosis/cell-cycle assays. (wu2024expressionandpotential pages 1-2)
In an ER+ breast cancer endocrine-therapy resistance expression study, TOP2A was upregulated in the recurrence group with log2 fold change 0.79 and p = 0.0381 (median follow-up 68 months; recurrence in 14/79 patients). (ong2023prognosticsignificanceof pages 3-5)
Some requested quantitative outputs (e.g., hazard ratios and confidence intervals for TOP2A survival associations in cholangiocarcinoma; numeric effect sizes in the NSCLC mechanistic paper; quantitative results from the ovarian AKT/mTOR paper; and more details from the endocrine-therapy resistance paper) were not present in the excerpted sections available to the evidence-gathering tool. The report therefore cites only quantitative values explicitly present in the retrieved text and flags where HRs/effect sizes are not available from the captured pages. (wu2024expressionandpotential pages 1-2, ong2023prognosticsignificanceof pages 3-5)
| Topic | Key findings | Primary citation IDs |
|---|---|---|
| Identity | • UniProt P11388 corresponds to human TOP2A / DNA topoisomerase IIα, a type IIA topoisomerase. • Homodimeric, ATP-dependent nuclear enzyme with N-terminal ATPase, central catalytic core, and C-terminal regulatory/chromatin-tethering region. |
(zhou2024advancesinresearch pages 2-4, matiasbarrios2023theimplicationof pages 2-4) |
| Catalytic reaction / mechanism | • Catalyzes ATP-dependent double-strand passage: binds a gate (G) DNA segment, cleaves both strands, passes a transported (T) duplex through, then religates DNA. • Uses an active-site tyrosine to form a covalent 5′-phosphotyrosyl TOP2A-DNA intermediate during transient DSB formation. • Mg2+ and ATP hydrolysis drive conformational changes and completion of the catalytic cycle. |
(zhou2024advancesinresearch pages 2-4, matiasbarrios2023theimplicationof pages 2-4, matiasbarrios2023theimplicationof media f3b15698) |
| Substrates / specificity | • Primary DNA-topology functions are decatenation of intertwined sister DNAs and relaxation of positive/negative supercoils. • Supports chromosome structural integrity and resolution of DNA entanglements generated during replication/mitosis rather than sequence-specific DNA recognition. |
(benoit2025investigatingthemitotic pages 21-25, matiasbarrios2023theimplicationof pages 2-4, benoit2025investigatingthemitotic pages 25-28) |
| Localization / cell-cycle role | • Predominantly nuclear; enriched on mitotic chromosome axes/scaffold and required for chromosome condensation, individualization, and segregation. • Expression is cell-cycle regulated, peaking in G2/M, and TOP2A remains chromosome-associated during mitosis. • No evidence supports TOP2A as a mitochondrial topoisomerase in human cells. |
(benoit2025investigatingthemitotic pages 21-25, matiasbarrios2023theimplicationof pages 2-4, benoit2025investigatingthemitotic pages 25-28) |
| Regulation / PTMs | • The C-terminal domain (CTD) contains nuclear localization information and a chromatin-tethering region important for mitotic chromosome binding. • CTD undergoes diverse post-translational modifications that modulate catalytic activity and protein interactions. • Function is linked to the decatenation checkpoint and influenced by p53 status. |
(zhou2024advancesinresearch pages 2-4, borella2024targetingtop2ain pages 2-4) |
| Drug targeting / poisons vs catalytic inhibitors | • TOP2 poisons (e.g., etoposide, doxorubicin/adriamycin, amsacrine) stabilize the cleavage complex after DNA breakage, increasing persistent DNA damage. • Catalytic inhibitors (e.g., ICRF-193, merbarone, ATPase-directed agents) inhibit cycle progression without necessarily stabilizing covalent TOP2A-DNA complexes. • Drug mechanism differences are central to efficacy, toxicity, and checkpoint responses. |
(benoit2025investigatingthemitotic pages 21-25, zhou2024advancesinresearch pages 9-11, matiasbarrios2023theimplicationof media f3b15698) |
| Recent cancer genomics / prognostic statistics | • Review data across ~24,000 solid tumors found ~4% TOP2A amplification; among 4,903 tumors, 129 (2.6%) showed TOP2A-HER2 co-amplification; >40% co-amplification reported in some breast/ovarian/gastroesophageal/pancreatic subsets. • In 182 iCCA patients, high TOP2A expression associated with worse OS/DSS/MFS (all p < 0.0001). • Recurrent somatic variants such as p.K743N are linked to characteristic mutational signatures/genome instability. |
(zhou2024advancesinresearch pages 1-2, ong2023prognosticsignificanceof pages 1-2, ong2023prognosticsignificanceof pages 3-5) |
| Recent mechanistic cancer findings | • In NSCLC, TOP2A upregulation promoted migration, invasion, EMT, and survival; knockdown reduced these phenotypes, with effects tied to Wnt/β-catenin/Wnt3a signaling. • In ovarian cancer, TOP2A knockdown caused G1 arrest, apoptosis, and reduced proliferation, with rescue implicating AKT/mTOR signaling. • In endocrine-therapy-resistant ER+ breast cancer, TOP2A was upregulated (log2FC 0.79, p = 0.0381) and correlated with proliferation-associated recurrence risk. |
(wu2024expressionandpotential pages 1-2, ong2023prognosticsignificanceof pages 3-5) |
Table: This table condenses the key functional annotation points for human TOP2A, covering its verified identity, enzymatic mechanism, localization, regulation, drug interactions, and recent cancer-related findings. It is useful as a compact evidence map linking core biology to clinically relevant research.
References
(zhou2024advancesinresearch pages 2-4): Tao Zhou, Yiting Niu, and Yanjun Li. Advances in research on malignant tumors and targeted agents for top2a (review). Molecular Medicine Reports, Dec 2024. URL: https://doi.org/10.3892/mmr.2024.13415, doi:10.3892/mmr.2024.13415. This article has 11 citations and is from a peer-reviewed journal.
(matiasbarrios2023theimplicationof pages 2-4): Victor M. Matias-Barrios and Xuesen Dong. The implication of topoisomerase ii inhibitors in synthetic lethality for cancer therapy. Pharmaceuticals, 16:94, Jan 2023. URL: https://doi.org/10.3390/ph16010094, doi:10.3390/ph16010094. This article has 35 citations.
(matiasbarrios2023theimplicationof media f3b15698): Victor M. Matias-Barrios and Xuesen Dong. The implication of topoisomerase ii inhibitors in synthetic lethality for cancer therapy. Pharmaceuticals, 16:94, Jan 2023. URL: https://doi.org/10.3390/ph16010094, doi:10.3390/ph16010094. This article has 35 citations.
(benoit2025investigatingthemitotic pages 21-25): J Benoit. Investigating the mitotic roles of topoisomerase 2 alpha and topoisomerase 2 beta-binding protein 1 in the maintenance of chromosome structure and genome …. Unknown journal, 2025.
(benoit2025investigatingthemitotic pages 25-28): J Benoit. Investigating the mitotic roles of topoisomerase 2 alpha and topoisomerase 2 beta-binding protein 1 in the maintenance of chromosome structure and genome …. Unknown journal, 2025.
(borella2024targetingtop2ain pages 2-4): Fulvio Borella, Stefano Fucina, Ylenia Seminara, Pietro Denti, Domenico Ferraioli, Luca Bertero, Niccolò Gallio, Jessica Cusato, Giorgio Valabrega, Alberto Revelli, Luca Marozio, and Stefano Cosma. Targeting top2a in ovarian cancer: biological and clinical implications. Current Oncology, 31:8054-8074, Dec 2024. URL: https://doi.org/10.3390/curroncol31120594, doi:10.3390/curroncol31120594. This article has 8 citations.
(zhou2024advancesinresearch pages 9-11): Tao Zhou, Yiting Niu, and Yanjun Li. Advances in research on malignant tumors and targeted agents for top2a (review). Molecular Medicine Reports, Dec 2024. URL: https://doi.org/10.3892/mmr.2024.13415, doi:10.3892/mmr.2024.13415. This article has 11 citations and is from a peer-reviewed journal.
(zhou2024advancesinresearch pages 1-2): Tao Zhou, Yiting Niu, and Yanjun Li. Advances in research on malignant tumors and targeted agents for top2a (review). Molecular Medicine Reports, Dec 2024. URL: https://doi.org/10.3892/mmr.2024.13415, doi:10.3892/mmr.2024.13415. This article has 11 citations and is from a peer-reviewed journal.
(ong2023prognosticsignificanceof pages 1-2): Khaa Hoo Ong, Hong-Yue Lai, Ding-Ping Sun, Tzu-Ju Chen, Steven Kuan-Hua Huang, Yu-Feng Tian, Chia-Lin Chou, Yow-Ling Shiue, Ti-Chun Chan, Chien-Feng Li, and Yu-Hsuan Kuo. Prognostic significance of dna topoisomerase ii alpha (top2a) in cholangiocarcinoma. Frontiers in bioscience, 28 4:75, Apr 2023. URL: https://doi.org/10.31083/j.fbl2804075, doi:10.31083/j.fbl2804075. This article has 7 citations and is from a peer-reviewed journal.
(ong2023prognosticsignificanceof pages 3-5): Khaa Hoo Ong, Hong-Yue Lai, Ding-Ping Sun, Tzu-Ju Chen, Steven Kuan-Hua Huang, Yu-Feng Tian, Chia-Lin Chou, Yow-Ling Shiue, Ti-Chun Chan, Chien-Feng Li, and Yu-Hsuan Kuo. Prognostic significance of dna topoisomerase ii alpha (top2a) in cholangiocarcinoma. Frontiers in bioscience, 28 4:75, Apr 2023. URL: https://doi.org/10.31083/j.fbl2804075, doi:10.31083/j.fbl2804075. This article has 7 citations and is from a peer-reviewed journal.
(wu2024expressionandpotential pages 1-2): Jiatao Wu, Wenjuan Li, Xueying Zhang, Fan Shi, Qianhao Jia, Yufei Wang, Yuqi Shi, Shiwu Wu, and Xiaojing Wang. Expression and potential molecular mechanism of top2a in metastasis of non-small cell lung cancer. Scientific Reports, May 2024. URL: https://doi.org/10.1038/s41598-024-63055-2, doi:10.1038/s41598-024-63055-2. This article has 26 citations and is from a peer-reviewed journal.