Preventing excess replication origin activation to ensure genome stability

Thakur, Bhushan; Ray, Anagh; Redon, Christophe E.; Aladjem, Mirit I.

doi:10.1016/j.tig.2021.09.008

Cited by 8 publications

(3 citation statements)

References 122 publications

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“…To maintain genome integrity, DNA must be replicated completely, but only once per cell cycle [91]. Sophisticated origin licensing systems and regulated assembly of prereplication machinery play critical roles in preventing over-replication and consequent genome instability [92][93][94]. Because of these stringent controls, it is important to prevent disassembly of the replisome when replication forks encounter DNA lesions.…”

Section: Dna Lesion Bypass and Stressed Fork Protection Mechanismsmentioning

confidence: 99%

Cellular Responses to Widespread DNA Replication Stress

Nickoloff,

Jaiswal,

Sharma

et al. 2023

IJMS

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Replicative DNA polymerases are blocked by nearly all types of DNA damage. The resulting DNA replication stress threatens genome stability. DNA replication stress is also caused by depletion of nucleotide pools, DNA polymerase inhibitors, and DNA sequences or structures that are difficult to replicate. Replication stress triggers complex cellular responses that include cell cycle arrest, replication fork collapse to one-ended DNA double-strand breaks, induction of DNA repair, and programmed cell death after excessive damage. Replication stress caused by specific structures (e.g., G-rich sequences that form G-quadruplexes) is localized but occurs during the S phase of every cell division. This review focuses on cellular responses to widespread stress such as that caused by random DNA damage, DNA polymerase inhibition/nucleotide pool depletion, and R-loops. Another form of global replication stress is seen in cancer cells and is termed oncogenic stress, reflecting dysregulated replication origin firing and/or replication fork progression. Replication stress responses are often dysregulated in cancer cells, and this too contributes to ongoing genome instability that can drive cancer progression. Nucleases play critical roles in replication stress responses, including MUS81, EEPD1, Metnase, CtIP, MRE11, EXO1, DNA2-BLM, SLX1-SLX4, XPF-ERCC1-SLX4, Artemis, XPG, FEN1, and TATDN2. Several of these nucleases cleave branched DNA structures at stressed replication forks to promote repair and restart of these forks. We recently defined roles for EEPD1 in restarting stressed replication forks after oxidative DNA damage, and for TATDN2 in mitigating replication stress caused by R-loop accumulation in BRCA1-defective cells. We also discuss how insights into biological responses to genome-wide replication stress can inform novel cancer treatment strategies that exploit synthetic lethal relationships among replication stress response factors.

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Section: Dna Lesion Bypass and Stressed Fork Protection Mechanismsmentioning

confidence: 99%

Cellular Responses to Widespread DNA Replication Stress

Nickoloff,

Jaiswal,

Sharma

et al. 2023

IJMS

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show abstract

“…Origin re-firing is minimized by the temporal separation of licensing and activation: ORC, CDC6, and CDT1 proteins attract the MCM helicase to form pre-replicative complexes (pre-RCs) in G1, whereas CDK and DDK kinases promote full replisome assembly and DNA synthesis in S phase (reviewed by Limas and Cook, 2019 ). Following origin activation, re-licensing is restricted by overlapping mechanisms (Thakur et al, 2022 ). At least three pre-RC components (ORC1, CDC6, and CDT1) are targeted by ubiquitin ligases (Méndez et al, 2002 ; Tatsumi et al, 2003 ; Arias and Walter, 2006 ; Nishitani et al, 2006 ; Walter et al, 2016 ).…”

Section: Introductionmentioning

confidence: 99%

RAD51 restricts DNA over-replication from re-activated origins

Muñoz,

Blanco-Romero,

González-Acosta

et al. 2024

EMBO J

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Eukaryotic cells rely on several mechanisms to ensure that the genome is duplicated precisely once in each cell division cycle, preventing DNA over-replication and genomic instability. Most of these mechanisms limit the activity of origin licensing proteins to prevent the reactivation of origins that have already been used. Here, we have investigated whether additional controls restrict the extension of re-replicated DNA in the event of origin re-activation. In a genetic screening in cells forced to re-activate origins, we found that re-replication is limited by RAD51 and enhanced by FBH1, a RAD51 antagonist. In the presence of chromatin-bound RAD51, forks stemming from re-fired origins are slowed down, leading to frequent events of fork reversal. Eventual re-initiation of DNA synthesis mediated by PRIMPOL creates ssDNA gaps that facilitate the partial elimination of re-duplicated DNA by MRE11 exonuclease. In the absence of RAD51, these controls are abrogated and re-replication forks progress much longer than in normal conditions. Our study uncovers a safeguard mechanism to protect genome stability in the event of origin reactivation.

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“…In eukaryotes, this process is highly regulated to ensure that all chromosomes replicate once per cell cycle. An impairment of this process results in abnormal DNA replication, which can lead to genomic instability and promote senescence or oncogenesis (Thakur et al , 2022).…”

mentioning

confidence: 99%

Orc6 dissociation from chromatin prevents premature loading of MCM at G2 and tetraploid production

Hayashi-Takanaka,

Hiratani,

Haraguchi

et al. 2024

Preprint

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DNA replication is tightly regulated to occur only once per cell cycle. The untimely initiation of DNA replication can result in genome instability, leading to aneuploidy, which has been associated with early senescence and cancer. The pre-replication complex, comprising the origin recognition complex (ORC; Orc1-6), Cdc6, Cdt1, and MCM, is required for initiating DNA replication, although the function of Orc6 is yet to be elucidated. Here, we show that Orc6 dissociates from chromatin upon entering the S-phase and that the Orc6 dissociation depends on proteasome activity. Treatment that inhibits proteasome activity, which declines with aging, increases the senescence marker p21 levels, and promotes cell cycle arrest in human immortalized hTERT-RPE1 cells. This treatment induced large nuclei with high levels of chromatin-bound Orc6 and MCM without undergoing mitosis. When the proteasome activity recovered, those cells with high levels of chromatin-bound Orc6 and MCM proceeded to whole-genome DNA replication, confirming that they were tetraploid G1 cells. We propose that proteasome-dependent dissociation of Orc6 from chromatin after S-phase is essential for preventing MCM reloading and the subsequent development of tetraploid cells.

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Preventing excess replication origin activation to ensure genome stability

Cited by 8 publications

References 122 publications

Cellular Responses to Widespread DNA Replication Stress

Cellular Responses to Widespread DNA Replication Stress

RAD51 restricts DNA over-replication from re-activated origins

Orc6 dissociation from chromatin prevents premature loading of MCM at G2 and tetraploid production

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