scholarly journals BLM Deficiency Is Not Associated with Sensitivity to Hydroxyurea-Induced Replication Stress

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Kenza Lahkim Bennani-Belhaj ◽  
Géraldine Buhagiar-Labarchède ◽  
Nada Jmari ◽  
Rosine Onclercq-Delic ◽  
Mounira Amor-Guéret
Keyword(s):  
High Risk ◽  
Chromosomal Instability ◽  
Replication Fork ◽  
Replication Stress ◽  
Clonogenic Survival ◽  
Early Age ◽  
Replication Forks ◽  
Cellular Models ◽  
Bloom’S Syndrome ◽  
Risk Of Cancer

Bloom's syndrome (BS) displays one of the strongest known correlations between chromosomal instability and a high risk of cancer at an early age. BS cells combine a reduced average fork velocity with constitutive endogenous replication stress. However, the response of BS cells to replication stress induced by hydroxyurea (HU), which strongly slows the progression of replication forks, remains unclear due to publication of conflicting results. Using two different cellular models of BS, we showed that BLM deficiency is not associated with sensitivity to HU, in terms of clonogenic survival, DSB generation, and SCE induction. We suggest that surviving BLM-deficient cells are selected on the basis of their ability to deal with an endogenous replication stress induced by replication fork slowing, resulting in insensitivity to HU-induced replication stress.

scholarly journals Seminoma in Undescended Intra Abdominal Testis: A Case Report

1970 ◽  
Vol 18 (2) ◽  
pp. 131-133 ◽  
Author(s):  
MM Haque ◽  
AB Siddique ◽  
ABMG Rabbani ◽  
MA Quasem ◽  
AKMG Rahman ◽  
...  
Keyword(s):  
Case Report ◽  
High Risk ◽  
Testicular Tumor ◽  
Early Age ◽  
Sexually Active ◽  
Lower Abdomen ◽  
Undescended Testes ◽  
Cryptorchid Testis ◽  
Risk Of Cancer ◽  
Abdominal Testis

A mass in the lower abdomen in a sexually active man with a cryptorchid testis strongly points towards the diagnosis of malignancy in the abdominal testis.1 The incidence of testicular tumor is 11 times more in inguinal testes and 50 times more in intra abdominal testes. 2 Normally, the testes, which are inside the abdomen during gestation, migrate into the scrotum by the time of birth. Occasionally, boys are born with testes that are still in the abdomen or in the groin, not having completed their journey to the scrotum. These undescended testes are at high risk of cancer and should be moved into the scrotum at an early age or removed entirely.   doi: 10.3329/taj.v18i2.3194 TAJ 2005; 18(2): 131-133

scholarly journals Mms1 and Mms22 stabilize the replisome during replication stress

2011 ◽  
Vol 22 (13) ◽  
pp. 2396-2408 ◽  
Author(s):  
Jessica A. Vaisica ◽  
Anastasija Baryshnikova ◽  
Michael Costanzo ◽  
Charles Boone ◽  
Grant W. Brown
Keyword(s):  
Dna Replication ◽  
Ubiquitin Ligase ◽  
Replication Fork ◽  
E3 Ubiquitin Ligase ◽  
Replication Stress ◽  
Replication Forks ◽  
Replication Fork Progression ◽  
Binding Partners ◽  
Efficient Recovery ◽  
Stalled Replication Forks

Mms1 and Mms22 form a Cul4Ddb1-like E3 ubiquitin ligase with the cullin Rtt101. In this complex, Rtt101 is bound to the substrate-specific adaptor Mms22 through a linker protein, Mms1. Although the Rtt101Mms1/Mms22ubiquitin ligase is important in promoting replication through damaged templates, how it does so has yet to be determined. Here we show that mms1Δ and mms22Δ cells fail to properly regulate DNA replication fork progression when replication stress is present and are defective in recovery from replication fork stress. Consistent with a role in promoting DNA replication, we find that Mms1 is enriched at sites where replication forks have stalled and that this localization requires the known binding partners of Mms1—Rtt101 and Mms22. Mms1 and Mms22 stabilize the replisome during replication stress, as binding of the fork-pausing complex components Mrc1 and Csm3, and DNA polymerase ε, at stalled replication forks is decreased in mms1Δ and mms22Δ. Taken together, these data indicate that Mms1 and Mms22 are important for maintaining the integrity of the replisome when DNA replication forks are slowed by hydroxyurea and thereby promote efficient recovery from replication stress.

scholarly journals SUMO-Based Regulation of Nuclear Positioning to Spatially Regulate Homologous Recombination Activities at Replication Stress Sites

Genes ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 2010
Author(s):  
Kamila Schirmeisen ◽  
Sarah A. E. Lambert ◽  
Karol Kramarz
Keyword(s):  
Homologous Recombination ◽  
Replication Fork ◽  
Replication Stress ◽  
Dna Lesions ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Replication Forks ◽  
Nuclear Positioning ◽  
Nuclear Compartment ◽  
Pore Complexes

DNA lesions have properties that allow them to escape their nuclear compartment to achieve DNA repair in another one. Recent studies uncovered that the replication fork, when its progression is impaired, exhibits increased mobility when changing nuclear positioning and anchors to nuclear pore complexes, where specific types of homologous recombination pathways take place. In yeast models, increasing evidence points out that nuclear positioning is regulated by small ubiquitin-like modifier (SUMO) metabolism, which is pivotal to maintaining genome integrity at sites of replication stress. Here, we review how SUMO-based pathways are instrumental to spatially segregate the subsequent steps of homologous recombination during replication fork restart. In particular, we discussed how routing towards nuclear pore complex anchorage allows distinct homologous recombination pathways to take place at halted replication forks.

scholarly journals ATAD5 restricts R-loop formation through PCNA unloading and RNA helicase maintenance at the replication fork

2020 ◽  
Author(s):  
Sangin Kim ◽  
Nalae Kang ◽  
Su Hyung Park ◽  
James Wells ◽  
Taejoo Hwang ◽  
...  
Keyword(s):  
Replication Fork ◽  
Replication Stress ◽  
S Phase ◽  
Replication Forks ◽  
Genomic Integrity ◽  
Loop Formation ◽  
Replication Rate ◽  
Rna Helicases ◽  
Dual Functions

Abstract R-loops are formed when replicative forks collide with the transcriptional machinery and can cause genomic instability. However, it is unclear how R-loops are regulated at transcription-replication conflict (TRC) sites and how replisome proteins are regulated to prevent R-loop formation or mediate R-loop tolerance. Here, we report that ATAD5, a PCNA unloader, plays dual functions to reduce R-loops both under normal and replication stress conditions. ATAD5 interacts with RNA helicases such as DDX1, DDX5, DDX21 and DHX9 and increases the abundance of these helicases at replication forks to facilitate R-loop resolution. Depletion of ATAD5 or ATAD5-interacting RNA helicases consistently increases R-loops during the S phase and reduces the replication rate, both of which are enhanced by replication stress. In addition to R-loop resolution, ATAD5 prevents the generation of new R-loops behind the replication forks by unloading PCNA which, otherwise, accumulates and persists on DNA, causing a collision with the transcription machinery. Depletion of ATAD5 reduces transcription rates due to PCNA accumulation. Consistent with the role of ATAD5 and RNA helicases in maintaining genomic integrity by regulating R-loops, the corresponding genes were mutated or downregulated in several human tumors.

scholarly journals RNF4 Regulates the BLM Helicase in Recovery From Replication Fork Collapse

2021 ◽  
Vol 12 ◽  
Author(s):  
Nathan Ellis ◽  
Jianmei Zhu ◽  
Mary K Yagle ◽  
Wei-Chih Yang ◽  
Jing Huang ◽  
...  
Keyword(s):  
Dna Replication ◽  
Replication Fork ◽  
Replication Stress ◽  
Dna Helicase ◽  
Replication Forks ◽  
Replication Origins ◽  
Dna Double Strand Breaks ◽  
Response Factors ◽  
Fork Stalling ◽  
In Cells

Sumoylation is an important enhancer of responses to DNA replication stress and the SUMO-targeted ubiquitin E3 ligase RNF4 regulates these responses by ubiquitylation of sumoylated DNA damage response factors. The specific targets and functional consequences of RNF4 regulation in response to replication stress, however, have not been fully characterized. Here we demonstrated that RNF4 is required for the restart of DNA replication following prolonged hydroxyurea (HU)-induced replication stress. Contrary to its role in repair of γ-irradiation-induced DNA double-strand breaks (DSBs), our analysis revealed that RNF4 does not significantly impact recognition or repair of replication stress-associated DSBs. Rather, using DNA fiber assays, we found that the firing of new DNA replication origins, which is required for replication restart following prolonged stress, was inhibited in cells depleted of RNF4. We also provided evidence that RNF4 recognizes and ubiquitylates sumoylated Bloom syndrome DNA helicase BLM and thereby promotes its proteosome-mediated turnover at damaged DNA replication forks. Consistent with it being a functionally important RNF4 substrate, co-depletion of BLM rescued defects in the firing of new replication origins observed in cells depleted of RNF4 alone. We concluded that RNF4 acts to remove sumoylated BLM from collapsed DNA replication forks, which is required to facilitate normal resumption of DNA synthesis after prolonged replication fork stalling and collapse.

scholarly journals The oncoprotein DEK affects the outcome of PARP1/2 inhibition during replication stress

2019 ◽  
Author(s):  
Magdalena Ganz ◽  
Christopher Vogel ◽  
Christina Czada ◽  
Vera Jörke ◽  
Rebecca Kleiner ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Replication Fork ◽  
Replication Stress ◽  
Tumor Formation ◽  
Replication Forks ◽  
Functional Link ◽  
Protein Levels ◽  
Replication Fork Progression ◽  
Dna Replication Stress ◽  
Architectural Protein

ABSTRACTDNA replication stress is a major source of genomic instability and is closely linked to tumor formation and progression. Poly(ADP-ribose)polymerases1/2 (PARP1/2) enzymes are activated in response to replication stress resulting in poly(ADP-ribose) (PAR) synthesis. PARylation plays an important role in the remodelling and repair of impaired replication forks, providing a rationale for targeting highly replicative cancer cells with PARP1/2 inhibitors. The human oncoprotein DEK is a unique, non-histone chromatin architectural protein whose deregulated expression is associated with the development of a wide variety of human cancers. Recently, we showed that DEK is a high-affinity target of PARylation and that it promotes the progression of impaired replication forks. Here, we investigated a potential functional link between PAR and DEK in the context of replication stress. Under conditions of mild replication stress induced either by topoisomerase1 inhibition with camptothecin or nucleotide depletion by hydroxyurea, we found that the effect of acute PARP1/2 inhibition on replication fork progression is dependent on DEK expression. Reducing DEK protein levels also overcomes the restart impairment of stalled forks provoked by blocking PARylation. Non-covalent DEK-PAR interaction via the central PAR-binding domain of DEK is crucial for counteracting PARP1/2 inhibition as shown for the formation of RPA positive foci in hydroxyurea treated cells. Finally, we show by iPOND and super resolved microscopy that DEK is not directly associated with the replisome since it binds to DNA at the stage of chromatin formation. Our report sheds new light on the still enigmatic molecular functions of DEK and suggests that DEK expression levels may influence the sensitivity of cancer cells to PARP1/2 inhibitors.

scholarly journals Non-enzymatic roles of human RAD51 at stalled replication forks

2018 ◽  
Author(s):  
Jennifer M. Mason ◽  
Yuen-Ling Chan ◽  
Ralph W. Weichselbaum ◽  
Douglas K. Bishop
Keyword(s):  
Dna Binding ◽  
Replication Fork ◽  
Replication Stress ◽  
Strand Exchange ◽  
Replication Forks ◽  
Enzymatic Function ◽  
Replication Restart ◽  
Stalled Replication Forks ◽  
Exchange Activity ◽  
Human Rad51

ABSTRACTThe central recombination enzyme RAD51 has been implicated in replication fork processing and restart in response to replication stress. Here, we use a separation-of-function allele of RAD51 that retains DNA binding, but not strand exchange activity, to reveal mechanistic aspects of RAD51’s roles in the response to replication stress. We find that cells lacking RAD51 strand exchange activity protect replication forks from MRE11-dependent degradation, as expected from previous studies. Unexpectedly we find that RAD51’s strand exchange activity is not required to convert stalled forks to a form that can be degraded by DNA2. Such conversion was shown previously to require replication fork reversal, supporting a model in which fork reversal depends on a non-enzymatic function of RAD51. We also show RAD51 promotes replication restart by both strand exchange-dependent and strand exchange-independent mechanisms.

scholarly journals SLX4–XPF mediates DNA damage responses to replication stress induced by DNA–protein interactions

2020 ◽  
Vol 220 (1) ◽  
Author(s):  
Riko Ishimoto ◽  
Yota Tsuzuki ◽  
Tomoki Matsumura ◽  
Seiichiro Kurashige ◽  
Kouki Enokitani ◽  
...  
Keyword(s):  
Dna Damage ◽  
Protein Interactions ◽  
Chromosomal Instability ◽  
Replication Fork ◽  
Protein Complexes ◽  
Critical Role ◽  
Replication Stress ◽  
S Phase ◽  
Damage Response

The DNA damage response (DDR) has a critical role in the maintenance of genomic integrity during chromosome replication. However, responses to replication stress evoked by tight DNA–protein complexes have not been fully elucidated. Here, we used bacterial LacI protein binding to lacO arrays to make site-specific replication fork barriers on the human chromosome. These barriers induced the accumulation of single-stranded DNA (ssDNA) and various DDR proteins at the lacO site. SLX4–XPF functioned as an upstream factor for the accumulation of DDR proteins, and consequently, ATR and FANCD2 were interdependently recruited. Moreover, LacI binding in S phase caused underreplication and abnormal mitotic segregation of the lacO arrays. Finally, we show that the SLX4–ATR axis represses the anaphase abnormality induced by LacI binding. Our results outline a long-term process by which human cells manage nucleoprotein obstacles ahead of the replication fork to prevent chromosomal instability.

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