Shining light on drug discovery: optogenetic screening for TopBP1 biomolecular condensate inhibitors

Abstract Human topoisomerase IIβ binding protein 1 (TopBP1) is a scaffold protein involved in DNA replication initiation, DNA repair, transcription regulation, and checkpoint activation. TopBP1 forms nuclear condensates that act as a molecular switch to amplify ATR activity and promote the activatio...

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Bibliographic Details
Published in:NAR cancer Vol. 7; no. 4; p. zcaf041
Main Authors: Morano, Laura, Vie, Nadia, Aissanou, Adam, Hodroj, Dana, Garambois, Véronique, Fauvre, Alexandra, Promonet, Alexy, Egger, Tom, Bordignon, Benoît, Hassen-Khodja, Cédric, Fiachetti, Solène, Basbous, Jihane, Gongora, Céline, Constantinou, Angelos
Format: Journal Article
Language:English
Published: England Oxford University Press 01.12.2025
Subjects:
5-Fluorouracil
Animals
Antineoplastic Agents - pharmacology
Ataxia Telangiectasia Mutated Proteins - antagonists & inhibitors
Ataxia Telangiectasia Mutated Proteins - metabolism
Carrier Proteins - antagonists & inhibitors
Carrier Proteins - genetics
Carrier Proteins - metabolism
Cell Line, Tumor
Checkpoint Kinase 1 - metabolism
Chemotherapy
CHK1 protein
Chromatin
Clinical trials
Colorectal carcinoma
Condensates
DNA biosynthesis
DNA repair
DNA-Binding Proteins - antagonists & inhibitors
DNA-Binding Proteins - genetics
DNA-Binding Proteins - metabolism
Drug Discovery - methods
Drug resistance
Fluorouracil - administration & dosage
Fluorouracil - pharmacology
Gene regulation
High-throughput screening
High-Throughput Screening Assays - methods
Humans
Irinotecan
Irinotecan - pharmacology
Kinases
Mice
Nuclear Proteins - antagonists & inhibitors
Nuclear Proteins - genetics
Nuclear Proteins - metabolism
Quinacrine
Replication initiation
Signal Transduction - drug effects
Thimerosal
Toxicity
Transcription activation
Transcription initiation
ISSN:2632-8674, 2632-8674
Online Access:Get full text
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Summary:Abstract Human topoisomerase IIβ binding protein 1 (TopBP1) is a scaffold protein involved in DNA replication initiation, DNA repair, transcription regulation, and checkpoint activation. TopBP1 forms nuclear condensates that act as a molecular switch to amplify ATR activity and promote the activation of the checkpoint effector kinase Chk1. In cancer cells, ATR activity is crucial to tolerate the intrinsically high level of DNA lesions and obstacles that block replication fork progression. Thus, ATR inhibitors are currently tested in clinical trials, often in combination with chemotherapy drugs. However, resistance and toxicity are still major issues. The weak interactions that hold TopBP1 condensates together are highly sensitive to changes in the cellular milieu, suggesting that small molecules may alter the formation of TopBP1 condensates. Here, we developed a high-throughput screening system to identify TopBP1 condensation modulators. This system allowed us to identify FDA-approved drugs, including thimerosal and quinacrine, that inhibit TopBP1 condensation and block the activation of ATR/Chk1 signaling. Mechanistically, quinacrine impaired TopBP1’s ability to associate with chromatin, thereby interfering with its capacity to form condensates. Furthermore, quinacrine enhanced the therapeutic efficacy of 5-fluorouracil and irinotecan, components of the clinically used FOLFIRI regimen in a mouse model of peritoneal carcinomatosis from colorectal cancer. Graphical Abstract Graphical Abstract
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ISSN:2632-8674
2632-8674
DOI:10.1093/narcan/zcaf041