Sister chromatid exchanges induced by perturbed replication are formed independently of homologous recombination factors

Heijink, Anne Margriet; Stok, Colin; Porubský, David; Manolika, Eleni Maria; Kok, Yannick P; Everts, Maaike; Boer, H. Rudolf de; Audrey, Anastasia; Wierenga, Elles; Guryev, Victor; Spierings, Diana C.J.; Knipscheer, Puck; Chaudhuri, Arnab Ray; Lansdorp, Peter M.; Vugt, Marcel A.T.M. van

doi:10.1101/2021.09.17.460736

Cited by 3 publications

(2 citation statements)

References 95 publications

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“…7a,c). Thus, whereas CIP2A does not associate with interphase DSBs in the nucleus 30,32,37 , we propose that cytoplasmic CIP2A diffuses into ruptured micronuclei where it prematurely engages with micronuclear DSBs that accumulate throughout interphase. In agreement, a mutant CIP2A rescue lacking its NES was sufficient to restore fragment clustering in CIP2A KO cells (Fig.…”

Section: Micronuclear Cip2a-topbp1 Poises Acentric Fragments For Clus...mentioning

confidence: 69%

Mitotic clustering of pulverized chromosomes from micronuclei

Lin

Valle-Inclán

Mazzagatti

et al. 2022

Preprint

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Complex genome rearrangements can be generated by the catastrophic shattering of mis-segregated chromosomes trapped within micronuclei through a process known as chromothripsis. Since each chromosome harbors a single centromere, how acentric fragments derived from shattered chromosomes are inherited between daughter cells during mitosis remains unknown. Here we tracked micronucleated chromosomes by live-cell imaging and show that acentric fragments cluster in close spatial proximity throughout mitosis for biased partitioning to a single daughter cell. Mechanistically, the CIP2A-TOPB1 complex prematurely associates with DNA lesions within ruptured micronuclei during interphase, which poises chromosome fragments for clustering upon mitotic entry. Inactivation of CIP2A or TOPBP1 caused pulverized chromosomes to untether and disperse throughout the mitotic cell, consequently resulting in the mis-accumulation of DNA fragments in the cytoplasm. The inheritance of shattered chromosomes by a single daughter cell suggests that micronucleation can drive complex rearrangements that lack the DNA copy number oscillations characteristic of canonical chromothripsis. Comprehensive analysis of pan-cancer whole-genome sequencing data revealed clusters of DNA copy number-neutral rearrangements – termed balanced chromothripsis – across diverse cancer types resulting in the acquisition of known driver events. Thus, distinct patterns of chromothripsis can be explained by the spatial mitotic clustering of pulverized chromosomes from micronuclei.

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Section: Micronuclear Cip2a-topbp1 Poises Acentric Fragments For Clus...mentioning

confidence: 69%

Mitotic clustering of pulverized chromosomes from micronuclei

Lin

Valle-Inclán

Mazzagatti

et al. 2022

Preprint

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“…Specifically, exposed ssDNA becomes vulnerable to nuclease-mediated cleavage when the CMG replicative helicase is removed from stalled replication forks flanking an under-replicated locus [ 99 ]. Subsequent ligation of these cleaved DNA ends has been shown to cause deletions with microhomology at the break sites, reflecting the usage of POLθ [ 39 , 99 , 100 ]. Similar genomic scars were observed in BRCA-deficient tumors and HR-deficient cells, which experience perturbed replication and show increased numbers of mitotic DNA lesions [ 101 ].…”

Section: Consequences Of Unprocessed Mitotic Dna Damagementioning

confidence: 99%

Processing DNA lesions during mitosis to prevent genomic instability

Audrey

Haan

Vugt

et al. 2022

Biochemical Society Transactions

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Failure of cells to process toxic double-strand breaks (DSBs) constitutes a major intrinsic source of genome instability, a hallmark of cancer. In contrast with interphase of the cell cycle, canonical repair pathways in response to DSBs are inactivated in mitosis. Although cell cycle checkpoints prevent transmission of DNA lesions into mitosis under physiological condition, cancer cells frequently display mitotic DNA lesions. In this review, we aim to provide an overview of how mitotic cells process lesions that escape checkpoint surveillance. We outline mechanisms that regulate the mitotic DNA damage response and the different types of lesions that are carried over to mitosis, with a focus on joint DNA molecules arising from under-replication and persistent recombination intermediates, as well as DNA catenanes. Additionally, we discuss the processing pathways that resolve each of these lesions in mitosis. Finally, we address the acute and long-term consequences of unresolved mitotic lesions on cellular fate and genome stability.

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RHINO restricts MMEJ activity to mitosis

Sfeir

Brambati

Sacco

et al. 2023

Preprint

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DNA double-strand breaks (DSBs) are toxic lesions that can lead to genome instability if not properly repaired. Breaks incurred in G1 phase of the cell cycle are predominantly fixed by non-homologous end-joining (NHEJ), while homologous recombination (HR) is the primary repair pathway in S and G2. Microhomology-mediated end-joining (MMEJ) is intrinsically error-prone and considered a backup DSB repair pathway that becomes essential when HR and NHEJ are compromised. In this study, we uncover MMEJ as the major DSB repair pathway in M phase. Using CRISPR/Cas9-based synthetic lethal screens, we identify subunits of the 9-1-1 complex (RAD9A-HUS1-RAD1) and its interacting partner, RHINO, as critical MMEJ factors. Mechanistically, we show that the function of 9-1-1 and RHINO in MMEJ is inconsistent with their well-established role in ATR signaling. Instead, RHINO plays an unexpected and essential role in directing mutagenic repair to M phase by directly binding to Polymerase theta and promoting its recruitment to DSBs in mitosis. In addition, we provide evidence that mitotic MMEJ repairs persistent DNA damage that originates in S phase but is not repaired by HR. The latter findings could explain the synthetic lethal relationship between POLQ and BRCA1/2 and the synergistic effect of PolQ and PARP inhibitors. In summary, our study identifies MMEJ as the primary pathway for repairing DSBs during mitosis and highlights an unanticipated role for RHINO in directing mutagenic repair to M phase.

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Sister chromatid exchanges induced by perturbed replication are formed independently of homologous recombination factors

Cited by 3 publications

References 95 publications

Mitotic clustering of pulverized chromosomes from micronuclei

Mitotic clustering of pulverized chromosomes from micronuclei

Processing DNA lesions during mitosis to prevent genomic instability

RHINO restricts MMEJ activity to mitosis

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