Topoisomerase IIIβ protects from tumorigenesis and immune dysregulation.

Unlabelled: Topoisomerase III-beta (Top3b) reduces nucleic acid torsional stress and intertwining generated during RNA and DNA metabolism while protecting the genome from pathological R-loops, which otherwise result in DNA breakage and genome instability. By studying Top3b knockout mice (Top3b-KO), we find that the loss of Top3b accelerates the development of spontaneous lymphoid tumors arising in spleens and lymph nodes, the organs with prominent Top3b expression. Aging Top3b-KO mice also display splenomegaly and systemic immune alterations including neutrophilia and lymphopenia suggestive of chronic inflammation.

Targeting neddylation sensitizes colorectal cancer to topoisomerase I inhibitors by inactivating the DCAF13-CRL4 ubiquitin ligase complex.

Colorectal cancers (CRCs) are prevalent worldwide, yet current treatments remain inadequate. Using chemical genetic screens, we identify that co-inhibition of topoisomerase I (TOP1) and NEDD8 is synergistically cytotoxic in human CRC cells. Combination of the TOP1 inhibitor irinotecan or its bioactive metabolite SN38 with the NEDD8-activating enzyme inhibitor pevonedistat exhibits synergy in CRC patient-derived organoids and xenografts.

Resolution of R-loops by topoisomerase III-β (TOP3B) in coordination with the DEAD-box helicase DDX5.

The present study demonstrates how TOP3B is involved in resolving R-loops. We observed elevated R-loops in TOP3B knockout cells (TOP3BKO), which are suppressed by TOP3B transfection. R-loop-inducing agents, the topoisomerase I inhibitor camptothecin, and the splicing inhibitor pladienolide-B also induce higher R-loops in TOP3BKO cells.

Cancer/Testis Antigen 55 is required for cancer cell proliferation and mitochondrial DNA maintenance.

Cancer/Testis Antigens (CTAs) represent a group of proteins whose expression under physiological conditions is restricted to testis but activated in many human cancers. Also, it was observed that co-expression of multiple CTAs worsens the patient prognosis. Five CTAs were reported acting in mitochondria and we recently reported 147 transcripts encoded by 67 CTAs encoding for proteins potentially targeted to mitochondria.

The FDA-Approved Anthelmintic Pyrvinium Pamoate Inhibits Pancreatic Cancer Cells in Nutrient-Depleted Conditions by Targeting the Mitochondria.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal aggressive cancer, in part due to elements of the microenvironment (hypoxia, hypoglycemia) that cause metabolic network alterations. The FDA-approved antihelminthic pyrvinium pamoate (PP) has previously been shown to cause PDAC cell death, although the mechanism has not been fully determined. We demonstrated that PP effectively inhibited PDAC cell viability with nanomolar IC50 values (9-93 nmol/L) against a panel of PDAC, patient-derived, and murine organoid cell lines.

DNA and RNA Cleavage Complexes and Repair Pathway for TOP3B RNA- and DNA-Protein Crosslinks.

The present study demonstrates that topoisomerase 3B (TOP3B) forms both RNA and DNA cleavage complexes (TOP3Bccs) in vivo and reveals a pathway for repairing TOP3Bccs. For inducing and detecting cellular TOP3Bccs, we engineer a "self-trapping" mutant of TOP3B (R338W-TOP3B). Transfection with R338W-TOP3B induces R-loops, genomic damage, and growth defect, which highlights the importance of TOP3Bcc repair mechanisms.

Beyond the unwinding: role of TOP1MT in mitochondrial translation.

Mitochondria contain their own genome (mtDNA), encoding 13 proteins of the enzyme complexes of the oxidative phosphorylation. Synthesis of these 13 mitochondrial proteins requires a specific translation machinery, the mitoribosomes whose RNA components are encoded by the mtDNA, whereas more than 80 proteins are encoded by nuclear genes. It has been well established that mitochondrial topoisomerase I (TOP1MT) is important for mtDNA integrity and mitochondrial transcription as it prevents excessive mtDNA negative supercoiling and releases topological stress during mtDNA replication and transcription.

Mitochondrial tyrosyl-DNA phosphodiesterase 2 and its TDP2 short isoform.

Tyrosyl-DNA phosphodiesterase 2 (TDP2) repairs abortive topoisomerase II cleavage complexes. Here, we identify a novel short isoform of TDP2 (TDP2) expressed from an alternative transcription start site. TDP2 contains a mitochondrial targeting sequence, contributing to its enrichment in the mitochondria and cytosol, while full-length TDP2 contains a nuclear localization signal and the ubiquitin-associated domain in the N-terminus.

SLFN11 Blocks Stressed Replication Forks Independently of ATR.

SLFN11 sensitizes cancer cells to a broad range of DNA-targeted therapies. Here we show that, in response to replication stress induced by camptothecin, SLFN11 tightly binds chromatin at stressed replication foci via RPA1 together with the replication helicase subunit MCM3. Unlike ATR, SLFN11 neither interferes with the loading of CDC45 and PCNA nor inhibits the initiation of DNA replication but selectively blocks fork progression while inducing chromatin opening across replication initiation sites.

Topoisomerase poisoning by genistein in the intestine of rats.

The isoflavone genistein has been shown to act as topoisomerase II poison in various cell lines. Here, we address the question whether genistein is able to affect topoisomerase II in vivo. Juvenile male Wistar rats received either a single dose of genistein subcutaneously (s.

Lack of mitochondrial topoisomerase I (TOP1mt) impairs liver regeneration.

The liver has an exceptional replicative capacity following partial hepatectomy or chemical injuries. Cellular proliferation requires increased production of energy and essential metabolites, which critically depend on the mitochondria. To determine whether Top1mt, the vertebrate mitochondrial topoisomerase, is involved in this process, we studied liver regeneration after carbon tetrachloride (CCl4) administration.

Oxidative metabolism enhances the cytotoxic and genotoxic properties of the soy isoflavone daidzein.

Scope: Oxidative metabolism of daidzein (DAI) might result in the formation of hydroxylated metabolites. Here, we address the question whether these metabolites differ in their biological activity from the parent isoflavone, exemplified for the epidermal growth factor receptor and topoisomerase II, potentially resulting in an enhanced toxic profile.

Methods And Results: In contrast to DAI, 6-hydroxydaidzein (6-HO-DAI) and 8-hydroxydaidzein (8-HO-DAI) were found to inhibit the tyrosine kinase activity of the epidermal growth factor receptor in an ELISA-based test system, but showed no effects within cells.

Topoisomerase II-targeting properties of a grapevine-shoot extract and resveratrol oligomers.

Grapevine-shoot extracts (GSE), containing trans-resveratrol and resveratrol oligomers, are commercially available as food supplements. Considering the topoisomerase-targeting properties of trans-resveratrol, the question of whether GSE affect these enzymes, thereby potentially causing DNA damage, was addressed. In a decatenation assay, GSE potently suppressed the catalytic activity of topoisomerase IIα (≥5 μg/mL).

Synthesis, topoisomerase-targeting activity and growth inhibition of lycobetaine analogs.

The plant alkaloid lycobetaine has potent topoisomerase-targeting properties and shows anticancer activity. Based on these findings, several lycobetaine analogs were synthesized mainly differing in their substituents at 2, 8 and 9 position and their biological activities were evaluated. The topoisomerase-targeting properties and cytotoxicity of these structural analogs were assessed in the human gastric carcinoma cell line GXF251L.