# A high-throughput screening identifies MCM chromatin loading inhibitors targeting cells with increased replication origins

## TL;DR

A new compound, NSC-95397, was found to block DNA replication in fast-growing cells, making it a potential anti-cancer treatment.

## Contribution

A high-throughput screening method identified NSC-95397 as a novel MCM chromatin loading inhibitor targeting CDC6.

## Key findings

- NSC-95397 induces CDC6 protein degradation, preventing MCM chromatin loading.
- NSC-95397 promotes cell death in highly proliferative human cells and Xenopus embryos.
- Xenopus laevis egg extract is an effective tool for identifying replication origin assembly inhibitors.

## Abstract

Replication origin assembly is a pivotal step in chromosomal DNA replication. In this process, the ORC complex binds DNA and, together with the CDC6 and CDT1, promotes the loading of the MCM helicase. Chemicals targeting origin assembly might be useful to sensitize highly proliferative cancer cells. However, identifying such compounds is challenging due to the multistage nature of this process. Here, using Xenopus laevis egg extract we set up a high-throughput screening to isolate MCM chromatin loading inhibitors, which led to the identification of NSC-95397 as a powerful inhibitor of replication origin assembly that targets CDC6 protein and promotes its degradation. Using systems developed to test selective drug-induced lethality we show that NSC-95397 triggers cell death both in human cells and Xenopus embryos that have higher proliferative ability. These findings demonstrate the effectiveness of molecules disrupting DNA replication processes in targeting hyperproliferating cells, highlighting their potential as anti-cancer molecules.

•Xl egg extract is a powerful tool to identify replication origin assembly inhibitors•MCMs chromatin loading is a useful readout to screen for DNA replication inhibitors•NSC-95397 induces CDC6 protein degradation preventing MCM chromatin loading•NSC-95397 promotes cell death in highly proliferative human cells and Xenopus embryos

Xl egg extract is a powerful tool to identify replication origin assembly inhibitors

MCMs chromatin loading is a useful readout to screen for DNA replication inhibitors

NSC-95397 induces CDC6 protein degradation preventing MCM chromatin loading

NSC-95397 promotes cell death in highly proliferative human cells and Xenopus embryos

Biochemistry; Molecular biology; Cell biology