scholarly journals The yeast core spliceosome maintains genome integrity through R-loop prevention and α-tubulin expression

2018 ◽  
Author(s):  
Annie S. Tam ◽  
Veena Mathew ◽  
Tianna S. Sihota ◽  
Anni Zhang ◽  
Peter C. Stirling
Keyword(s):  
Gene Expression ◽  
Dna Replication ◽  
Chromosome Segregation ◽  
Genome Stability ◽  
Spindle Assembly Checkpoint ◽  
Genome Instability ◽  
Genome Integrity ◽  
Genome Maintenance ◽  
Maintenance Factors ◽  
Spindle Assembly Checkpoint Protein

To achieve genome stability cells must coordinate the action of various DNA transactions including DNA replication, repair, transcription and chromosome segregation. How transcription and RNA processing enable genome stability is only partly understood. Two predominant models have emerged: one involving changes in gene expression that perturb other genome maintenance factors, and another in which genotoxic DNA:RNA hybrids, called R-loops, impair DNA replication. Here we characterize genome instability phenotypes in a panel yeast splicing factor mutants and find that mitotic defects, and in some cases R-loop accumulation, are causes of genome instability. Genome instability in splicing mutants is exacerbated by loss of the spindle-assembly checkpoint protein Mad1. Moreover, removal of the intron from the α-tubulin gene TUB1 restores genome integrity. Thus, while R-loops contribute in some settings, defects in yeast splicing predominantly lead to genome instability through effects on gene expression.

scholarly journals Selective defects in gene expression control genome instability in yeast splicing mutants

2019 ◽  
Vol 30 (2) ◽  
pp. 191-200 ◽  
Author(s):  
Annie S. Tam ◽  
Tianna S. Sihota ◽  
Karissa L. Milbury ◽  
Anni Zhang ◽  
Veena Mathew ◽  
...  
Keyword(s):  
Gene Expression ◽  
Genome Stability ◽  
Spindle Assembly Checkpoint ◽  
Genome Instability ◽  
Genome Maintenance ◽  
Expression Control ◽  
Maintenance Factors ◽  
Gene Expression Control ◽  
Multiple Routes ◽  
Spindle Assembly Checkpoint Protein

RNA processing mutants have been broadly implicated in genome stability, but mechanistic links are often unclear. Two predominant models have emerged: one involving changes in gene expression that perturb other genome maintenance factors and another in which genotoxic DNA:RNA hybrids, called R-loops, impair DNA replication. Here we characterize genome instability phenotypes in yeast splicing factor mutants and find that mitotic defects, and in some cases R-loop accumulation, are causes of genome instability. In both cases, alterations in gene expression, rather than direct cis effects, are likely to contribute to instability. Genome instability in splicing mutants is exacerbated by loss of the spindle-assembly checkpoint protein Mad1. Moreover, removal of the intron from the α-tubulin gene TUB1 restores genome integrity. Thus, differing penetrance and selective effects on the transcriptome can lead to a range of phenotypes in conditional mutants of the spliceosome, including multiple routes to genome instability.

scholarly journals The RAD51 recombinase protects mitotic chromatin in human cells

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Isabel E. Wassing ◽  
Emily Graham ◽  
Xanita Saayman ◽  
Lucia Rampazzo ◽  
Christine Ralf ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Genome Stability ◽  
Spindle Assembly Checkpoint ◽  
De Novo ◽  
Genomic Stability ◽  
Human Cells ◽  
Genome Integrity ◽  
Chromosomal Replication ◽  
Anaphase Onset ◽  
Mitotic Chromatin

AbstractThe RAD51 recombinase plays critical roles in safeguarding genome integrity, which is fundamentally important for all living cells. While interphase functions of RAD51 in maintaining genome stability are well-characterised, its role in mitosis remains contentious. In this study, we show that RAD51 protects under-replicated DNA in mitotic human cells and, in this way, promotes mitotic DNA synthesis (MiDAS) and successful chromosome segregation. In cells experiencing mild replication stress, MiDAS was detected irrespective of mitotically generated DNA damage. MiDAS broadly required de novo RAD51 recruitment to single-stranded DNA, which was supported by the phosphorylation of RAD51 by the key mitotic regulator Polo-like kinase 1. Importantly, acute inhibition of MiDAS delayed anaphase onset and induced centromere fragility, suggesting a mechanism that prevents the satisfaction of the spindle assembly checkpoint while chromosomal replication remains incomplete. This study hence identifies an unexpected function of RAD51 in promoting genomic stability in mitosis.

scholarly journals Molecular connections between circadian rhythm and genome maintenance pathways

2020 ◽  
Author(s):  
Arun Mouli Kolinjivadi ◽  
Siao Ting Chong ◽  
Joanne Ngeow
Keyword(s):  
Cell Cycle ◽  
Dna Repair ◽  
Dna Replication ◽  
Circadian Clock ◽  
Genome Stability ◽  
Genome Instability ◽  
Model Systems ◽  
Genome Maintenance ◽  
Replication Fork Progression ◽  
Repair Efficiency

Co-ordinated oscillation of mammalian circadian clock and cell cycle is essential for cellular and organismal homeostasis. Existing preclinical, epidemiological, molecular and biochemical evidence reveal a robust interplay between circadian clock, genome instability and cancer. Furthermore, recent investigations have demonstrated that the alterations in circadian clock perturb genome stability by modulating the cell cycle timing, altering DNA replication fork progression, influencing DNA Damage Response (DDR) and DNA repair efficiency. In this review, we examine the most recent findings from different eukaryotic model systems and discuss the functional interaction between circadian factors with key DNA replication, DDR and DNA repair genes.

scholarly journals Multistep mechanism of DNA replication-coupled G-quadruplex resolution

2020 ◽  
Author(s):  
Koichi Sato ◽  
Nerea Martin-Pintado ◽  
Harm Post ◽  
Maarten Altelaar ◽  
Puck Knipscheer
Keyword(s):  
Dna Replication ◽  
Genome Stability ◽  
Genome Instability ◽  
Genome Maintenance ◽  
Replicative Helicase ◽  
Dna Structures ◽  
G Quadruplex ◽  
Egg Extracts ◽  
Leading Strand ◽  
Lagging Strand

SummaryG-quadruplex (or G4) structures are non-canonical DNA structures that form in guanine-rich sequences and threaten genome stability when not properly resolved. G4 unwinding occurs during S phase via an unknown mechanism. Using Xenopus egg extracts, we define a three-step G4 unwinding mechanism that is coupled to DNA replication. First, the replicative helicase (CMG) stalls at a leading strand G4 structure. Second, the DHX36 helicase mediates the bypass of the CMG past the intact G4 structure, which allows approach of the leading strand to the G4. Third, G4 structure unwinding by the FANCJ helicase enables the DNA polymerase to synthesize past the G4 motif. A G4 on the lagging strand template does not stall CMG, but still requires DNA replication for unwinding. DHX36 and FANCJ have partially redundant roles, conferring robustness to this pathway. Our data reveal a novel genome maintenance pathway that promotes faithful G4 replication thereby avoiding genome instability.

scholarly journals FBL17 targets CDT1a for degradation in early S-phase to prevent Arabidopsis genome instability

2019 ◽  
Author(s):  
Bénédicte Desvoyes ◽  
Sandra Noir ◽  
Kinda Masoud ◽  
María Isabel López ◽  
Pascal Genschik ◽  
...  
Keyword(s):  
Dna Replication ◽  
Genome Stability ◽  
Genome Instability ◽  
S Phase ◽  
Replication Initiation ◽  
Genome Integrity ◽  
Dependent Manner ◽  
Dna Replication Initiation ◽  
Oscillatory Pattern ◽  
F Box Protein

AbstractMaintenance of genome integrity depends on controlling the availability of DNA replication initiation proteins, e.g., CDT1, a component of the pre-replication complexes that regulates chromatin licensing for replication. To understand the evolutionary history of CDT1 regulation, we have identified the mechanisms involved in CDT1 dynamics. During cell cycle, CDT1a starts to be loaded early after mitotic exit and maintains high levels until the G1/S transition. Soon after the S-phase onset, CDT1a is rapidly degraded in a proteasome-dependent manner. Plant cells use a specific SCF-mediated pathway that relies on the FBL17 F-box protein for CDT1a degradation, which is independent of CUL4a-containing complexes. A similar oscillatory pattern occurs in endoreplicating cells, where CDT1a is loaded just after finishing the S-phase. CDT1a is necessary to maintain genome stability, an ancient strategy although unique proteins and mechanisms have evolved in different eukaryotic lineages to ensure its degradation during S-phase.Impact statementThe DNA replication protein CDT1a is crucial for genome integrity and is targeted for proteasome degradation just after S-phase initiation by FBL17 in proliferating and endoreplicating cells of Arabidopsis

scholarly journals Emerging Roles of RAD52 in Genome Maintenance

Cancers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1038 ◽  
Author(s):  
Manisha Jalan ◽  
Kyrie S. Olsen ◽  
Simon N. Powell
Keyword(s):  
Genome Stability ◽  
Genome Integrity ◽  
Repair Pathway ◽  
Genome Maintenance ◽  
Knock Out ◽  
Repair Protein ◽  
Attractive Therapeutic Target ◽  
Dna Repair Protein ◽  
Synthetically Lethal ◽  
Knock Out Mice

The maintenance of genome integrity is critical for cell survival. Homologous recombination (HR) is considered the major error-free repair pathway in combatting endogenously generated double-stranded lesions in DNA. Nevertheless, a number of alternative repair pathways have been described as protectors of genome stability, especially in HR-deficient cells. One of the factors that appears to have a role in many of these pathways is human RAD52, a DNA repair protein that was previously considered to be dispensable due to a lack of an observable phenotype in knock-out mice. In later studies, RAD52 deficiency has been shown to be synthetically lethal with defects in BRCA genes, making RAD52 an attractive therapeutic target, particularly in the context of BRCA-deficient tumors.

scholarly journals Heterochromatin: Guardian of the Genome

2018 ◽  
Vol 34 (1) ◽  
pp. 265-288 ◽  
Author(s):  
Aniek Janssen ◽  
Serafin U. Colmenares ◽  
Gary H. Karpen
Keyword(s):  
Chromosome Segregation ◽  
Genome Stability ◽  
Constitutive Heterochromatin ◽  
Repetitive Sequences ◽  
Genome Integrity ◽  
Chromatin Domain ◽  
Cellular Processes ◽  
Eukaryotic Nucleus ◽  
And Function ◽  
Heterochromatin Structure

Constitutive heterochromatin is a major component of the eukaryotic nucleus and is essential for the maintenance of genome stability. Highly concentrated at pericentromeric and telomeric domains, heterochromatin is riddled with repetitive sequences and has evolved specific ways to compartmentalize, silence, and repair repeats. The delicate balance between heterochromatin epigenetic maintenance and cellular processes such as mitosis and DNA repair and replication reveals a highly dynamic and plastic chromatin domain that can be perturbed by multiple mechanisms, with far-reaching consequences for genome integrity. Indeed, heterochromatin dysfunction provokes genetic turmoil by inducing aberrant repeat repair, chromosome segregation errors, transposon activation, and replication stress and is strongly implicated in aging and tumorigenesis. Here, we summarize the general principles of heterochromatin structure and function, discuss the importance of its maintenance for genome integrity, and propose that more comprehensive analyses of heterochromatin roles in tumorigenesis will be integral to future innovations in cancer treatment.

scholarly journals Alkyladenine DNA glycosylase associates with transcription elongation to coordinate DNA repair with gene expression

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Nicola P. Montaldo ◽  
Diana L. Bordin ◽  
Alessandro Brambilla ◽  
Marcel Rösinger ◽  
Sarah L. Fordyce Martin ◽  
...  
Keyword(s):  
Gene Expression ◽  
Genome Stability ◽  
Genome Instability ◽  
Excision Repair ◽  
Regulation Of Gene Expression ◽  
Direct Interaction ◽  
Dna Glycosylase ◽  
Pol Ii ◽  
Naked Dna ◽  
Alkyladenine Dna Glycosylase

AbstractBase excision repair (BER) initiated by alkyladenine DNA glycosylase (AAG) is essential for removal of aberrantly methylated DNA bases. Genome instability and accumulation of aberrant bases accompany multiple diseases, including cancer and neurological disorders. While BER is well studied on naked DNA, it remains unclear how BER efficiently operates on chromatin. Here, we show that AAG binds to chromatin and forms complex with RNA polymerase (pol) II. This occurs through direct interaction with Elongator and results in transcriptional co-regulation. Importantly, at co-regulated genes, aberrantly methylated bases accumulate towards the 3′end in regions enriched for BER enzymes AAG and APE1, Elongator and active RNA pol II. Active transcription and functional Elongator are further crucial to ensure efficient BER, by promoting AAG and APE1 chromatin recruitment. Our findings provide insights into genome stability maintenance in actively transcribing chromatin and reveal roles of aberrantly methylated bases in regulation of gene expression.

scholarly journals Chromatin-associated degradation is defined by UBXN-3/FAF1 to safeguard DNA replication fork progression

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
André Franz ◽  
Paul A. Pirson ◽  
Domenic Pilger ◽  
Swagata Halder ◽  
Divya Achuthankutty ◽  
...  
Keyword(s):  
Dna Replication ◽  
Dynamic Process ◽  
Metabolic Pathways ◽  
Replication Fork ◽  
Genome Instability ◽  
Genome Integrity ◽  
Substrate Selection ◽  
Replication Fork Progression ◽  
Replication Factors ◽  
Spatiotemporal Control

Abstract The coordinated activity of DNA replication factors is a highly dynamic process that involves ubiquitin-dependent regulation. In this context, the ubiquitin-directed ATPase CDC-48/p97 recently emerged as a key regulator of chromatin-associated degradation in several of the DNA metabolic pathways that assure genome integrity. However, the spatiotemporal control of distinct CDC-48/p97 substrates in the chromatin environment remained unclear. Here, we report that progression of the DNA replication fork is coordinated by UBXN-3/FAF1. UBXN-3/FAF1 binds to the licensing factor CDT-1 and additional ubiquitylated proteins, thus promoting CDC-48/p97-dependent turnover and disassembly of DNA replication factor complexes. Consequently, inactivation of UBXN-3/FAF1 stabilizes CDT-1 and CDC-45/GINS on chromatin, causing severe defects in replication fork dynamics accompanied by pronounced replication stress and eventually resulting in genome instability. Our work identifies a critical substrate selection module of CDC-48/p97 required for chromatin-associated protein degradation in both Caenorhabditis elegans and humans, which is relevant to oncogenesis and aging.

scholarly journals The Opposing Functions of Protein Kinases and Phosphatases in Chromosome Bipolar Attachment

2019 ◽  
Vol 20 (24) ◽  
pp. 6182 ◽  
Author(s):  
Delaney Sherwin ◽  
Yanchang Wang
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Model Organism ◽  
Eukaryotic Cells ◽  
Genome Integrity ◽  
Chromosome Missegregation ◽  
Spindle Poles ◽  
Mitosis And Meiosis

Accurate chromosome segregation during cell division is essential to maintain genome integrity in all eukaryotic cells, and chromosome missegregation leads to aneuploidy and therefore represents a hallmark of many cancers. Accurate segregation requires sister kinetochores to attach to microtubules emanating from opposite spindle poles, known as bipolar attachment or biorientation. Recent studies have uncovered several mechanisms critical to chromosome bipolar attachment. First, a mechanism exists to ensure that the conformation of sister centromeres is biased toward bipolar attachment. Second, the phosphorylation of some kinetochore proteins destabilizes kinetochore attachment to facilitate error correction, but a protein phosphatase reverses this phosphorylation. Moreover, the activity of the spindle assembly checkpoint is regulated by kinases and phosphatases at the kinetochore, and this checkpoint prevents anaphase entry in response to faulty kinetochore attachment. The fine-tuned kinase/phosphatase balance at kinetochores is crucial for faithful chromosome segregation during both mitosis and meiosis. Here, we discuss the function and regulation of protein phosphatases in the establishment of chromosome bipolar attachment with a focus on the model organism budding yeast.

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