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Recql5 plays an important role in DNA replication and cell survival after camptothecin treatment.

ABSTRACT: Disruption of replication can lead to loss of genome integrity and increase of cancer susceptibility in mammals. Thus, a replication impediment constitutes a formidable challenge to these organisms. Recent studies indicate that homologous recombination (HR) plays an important role in suppressing genome instability and promoting cell survival after exposure to various replication inhibitors, including a topoisomerase I inhibitor, camptothecin (CPT). Here, we report that the deletion of RecQ helicase Recql5 in mouse ES cells and embryonic fibroblast (MEF) cells resulted in a significant increase in CPT sensitivity and a profound reduction in DNA replication after the treatment with CPT, but not other DNA-damaging agents. This CPT-induced cell death is replication dependent and occurs primarily after the cells had exited the first cell cycle after CPT treatment. Furthermore, we show that Recql5 functions nonredundantly with Rad51, a key factor for HR to protect mouse ES cells from CPT-induced cytotoxicity. These new findings strongly suggest that Recql5 plays an important role in maintaining active DNA replication to prevent the collapse of replication forks and the accumulation of DSBs in order to preserve genome integrity and to prevent cell death after replication stress as a result of topoisomerase I poisoning.

SUBMITTER: Hu Y

PROVIDER: S-EPMC2613109 | biostudies-literature | 2009 Jan

REPOSITORIES: biostudies-literature

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Recql5 plays an important role in DNA replication and cell survival after camptothecin treatment.

Hu Yiduo Y Lu Xincheng X Zhou Guangjin G Barnes Ellen L EL Luo Guangbin G

Molecular biology of the cell 20081105 1

Disruption of replication can lead to loss of genome integrity and increase of cancer susceptibility in mammals. Thus, a replication impediment constitutes a formidable challenge to these organisms. Recent studies indicate that homologous recombination (HR) plays an important role in suppressing genome instability and promoting cell survival after exposure to various replication inhibitors, including a topoisomerase I inhibitor, camptothecin (CPT). Here, we report that the deletion of RecQ helic ...[more]

PMID: 18987339

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Project description:DNA topoisomerase I (Top1) and topoisomerase II (Top2) inhibitors are widely used to treat a variety of cancers. Their mechanism of action involves stabilization of otherwise transient ("cleavable") complexes between Top1 or Top2 and DNA; collisions of DNA replication forks with such stabilized complexes lead to formation of DNA double-strand breaks (DSBs). In this study, using 5-ethynyl-2'deoxyuridine (EdU) as a DNA precursor, we directly assessed the relationship between DNA replication and induction of DSBs revealed as ?H2AX foci in A549 cells treated with Top1 inhibitors topotecan (Tpt) or camptothecin (Cpt) and Top2 inhibitors mitoxantrone (Mxt) and etoposide (Etp). Analysis of cells by multiparameter laser scanning cytometry following treatment with Tpt or Cpt revealed that only DNA replicating cells showed induction of ?H2AX and a strong correlation between DNA replication and formation of DSBs (r = 0.86). In cells treated with Mxt or Etp, the correlation was weaker (r = 0.52 and 0.64). In addition, both Mtx and Etp caused induction of ?H2AX in cells not replicating DNA. Confocal imaging of nuclei of cells treated with Tpt revealed the presence of ?H2AX foci predominantly in DNA replicating cells and close association and co-localization of ?H2AX foci with DNA replication sites. In cells treated with Mxt or Etp, the ?H2AX foci were induced in DNA replicating as well as non-replicating cells but the close association between a large proportion of ?H2AX foci and DNA replication sites was also apparent. The data are consistent with the view that collision of DNA replication forks with cleavable Top1-DNA complexes stabilized by Tpt/Cpt is the sole cause of induction of DSBs. Additional mechanisms such as involvement of transcription and/or generation of oxidative stress may contribute to DSBs induction by Mxt and Etp. The confocal analysis of the association between DNA replication sites and the sites of DSBs (?H2AX foci) opens a new approach for mechanistic studies of the involvement of DNA replication in induction of DNA damage.

Dataset Information

Recql5 plays an important role in DNA replication and cell survival after camptothecin treatment.

Publications

Recql5 plays an important role in DNA replication and cell survival after camptothecin treatment.

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