scholarly journals Ubiquitin/SUMO modification of PCNA promotes replication fork progression in Xenopus laevis egg extracts

2005 ◽  
Vol 171 (6) ◽  
pp. 947-954 ◽  
Author(s):  
Craig A. Leach ◽  
W. Matthew Michael
Keyword(s):  
Xenopus Laevis ◽  
Replication Fork ◽  
Nuclear Antigen ◽  
Molecular Gas ◽  
Chromosomal Replication ◽  
Dna Templates ◽  
Replication Fork Progression ◽  
Egg Extracts ◽  
The Impact ◽  
Proliferating Cell

The homotrimeric DNA replication protein proliferating cell nuclear antigen (PCNA) is regulated by both ubiquitylation and sumoylation. We study the appearance and the impact of these modifications on chromosomal replication in frog egg extracts. Xenopus laevis PCNA is modified on lysine 164 by sumoylation, monoubiquitylation, and diubiquitylation. Sumoylation and monoubiquitylation occur during the replication of undamaged DNA, whereas diubiquitylation occurs specifically in response to DNA damage. When lysine 164 modification is prevented, replication fork movement through undamaged DNA slows down and DNA polymerase δ fails to associate with replicating chromatin. When sumoylation alone is prevented, replication occurs normally and neither monoubiquitylation nor sumoylation are required for the replication of simple single-strand DNA templates. Our findings expand the repertoire of functions for PCNA ubiquitylation and sumoylation by elucidating a role for these modifications during the replication of undamaged DNA. Furthermore, they suggest that PCNA monoubiquitylation serves as a molecular gas pedal that controls the speed of replisome movement during S phase.

scholarly journals DNA damage-induced replication arrest in Xenopus egg extracts

2003 ◽  
Vol 163 (2) ◽  
pp. 245-255 ◽  
Author(s):  
Matthew P. Stokes ◽  
W. Matthew Michael
Keyword(s):  
Dna Damage ◽  
Proliferating Cell Nuclear Antigen ◽  
Replication Fork ◽  
Nuclear Antigen ◽  
Chromosomal Replication ◽  
Replication Arrest ◽  
Egg Extracts ◽  
Xenopus Egg ◽  
Xenopus Egg Extracts ◽  
Proliferating Cell

Chromosomal replication is sensitive to the presence of DNA-damaging alkylating agents, such as methyl methanesulfonate (MMS). MMS is known to inhibit replication though activation of the DNA damage checkpoint and through checkpoint-independent slowing of replication fork progression. Using Xenopus egg extracts, we now report an additional pathway that is stimulated by MMS-induced damage. We show that, upon incubation in egg extracts, MMS-treated DNA activates a diffusible inhibitor that blocks, in trans, chromosomal replication. The downstream effect of the inhibitor is a failure to recruit proliferating cell nuclear antigen, but not DNA polymerase α, to the nascent replication fork. Thus, alkylation damage activates an inhibitor that intercepts the replication pathway at a point between the polymerase α and proliferating cell nuclear antigen execution steps. We also show that activation of the inhibitor does not require the DNA damage checkpoint; rather, stimulation of the pathway described here results in checkpoint activation. These data describe a novel replication arrest pathway, and they also provide an example of how subpathways within the DNA damage response network are integrated to promote efficient cell cycle arrest in response to damaged DNA.

The Impact of 5-Azacytidine on Placental Weight, Glycoprotein Pattern and Proliferating Cell Nuclear Antigen Expression in Rat Placenta

Placenta ◽  
2007 ◽  
Vol 28 (8-9) ◽  
pp. 803-811 ◽  
Author(s):  
L. Šerman ◽  
M. Vlahović ◽  
M. Šijan ◽  
F. Bulić-Jakuš ◽  
A. Šerman ◽  
...  
Keyword(s):  
Proliferating Cell Nuclear Antigen ◽  
Antigen Expression ◽  
Placental Weight ◽  
Nuclear Antigen ◽  
The Impact ◽  
Proliferating Cell

scholarly journals Ovarian surface epithelium of hypothyroid newborn and neonatal rats: From proliferating cell nuclear antigen and caspase-3 perspectives

2018 ◽  
Vol 72 (2) ◽  
pp. 80-89
Author(s):  
Anita Radovanovic ◽  
Milica Kovacevic-Filipovic ◽  
Ivan Milosevic ◽  
Tijana Luzajic ◽  
Stefan Velickovic ◽  
...  
Keyword(s):  
Proliferating Cell Nuclear Antigen ◽  
Caspase 3 ◽  
Ovarian Surface Epithelium ◽  
Female Rats ◽  
Nuclear Antigen ◽  
Surface Epithelium ◽  
Ovarian Surface ◽  
Cell Height ◽  
The Impact ◽  
Proliferating Cell

Introduction. The ovarian surface epithelium (OSE) undergoes intensive regeneration and remodeling after each ovulation during the whole reproductive period. This process increases the risk of one of the most common ovarian tumors in women and the female dog. Considering the fact that maternal hypothyroidism highly impacts cell proliferation and cell death during folliculogenesis in the early neonatal period, we aimed to analyze its effect on OSE morphology and dynamics. Materials and Methods. The study was performed on newborn (24-h-old) and neonatal (4-day-old) female rats, a randomized trial between the control and hypothyroid groups, born under controlled circumstances and hypothyroid mothers, respectively. Their ovaries were analyzed histologically and processed to determine the OSE cell height as an average value of four measurement points. Also, the immunopositivity of the proliferating cell nuclear antigen (PCNA) and caspase-3 were assessed semiquantitatively. Results and Conclusions. No major structural differences of OSE were found between groups within the given ages except for a slight increment of OSE cell height and incompleteness of apical cell membrane with cytoplasmic projections in hypothyroid animals. PCNA immunopositivity of the OSE cells was higher in ovaries of hypothyroid animals of both ages in comparison to the controls. Moreover, only scarce OSE cells were caspase-3 positive in both groups and ages, with no difference in immunopositivity. Our study confirms the impact of hypothyroidism in the early postnatal period on morphology and proliferation rate of OSE cells, with no effect on caspase-3 dependent cell removal, which may serve as a premise for future investigation of potential carcinogenesis, in terms of prevention and treatment of ovarian cancer.

scholarly journals Single-molecule imaging reveals control of parental histone recycling by free histones during DNA replication

2020 ◽  
Vol 6 (38) ◽  
pp. eabc0330 ◽  
Author(s):  
D. T. Gruszka ◽  
S. Xie ◽  
H. Kimura ◽  
H. Yardimci
Keyword(s):  
Dna Replication ◽  
Real Time ◽  
Single Molecule ◽  
Replication Fork ◽  
Epigenetic Inheritance ◽  
Replication Forks ◽  
Replication Fork Progression ◽  
Egg Extracts ◽  
Fork Stalling ◽  
The Moment

During replication, nucleosomes are disrupted ahead of the replication fork, followed by their reassembly on daughter strands from the pool of recycled parental and new histones. However, because no previous studies have managed to capture the moment that replication forks encounter nucleosomes, the mechanism of recycling has remained unclear. Here, through real-time single-molecule visualization of replication fork progression in Xenopus egg extracts, we determine explicitly the outcome of fork collisions with nucleosomes. Most of the parental histones are evicted from the DNA, with histone recycling, nucleosome sliding, and replication fork stalling also occurring but at lower frequencies. Critically, we find that local histone recycling becomes dominant upon depletion of endogenous histones from extracts, revealing that free histone concentration is a key modulator of parental histone dynamics at the replication fork. The mechanistic details revealed by these studies have major implications for our understanding of epigenetic inheritance.

scholarly journals Geminivirus C3 Protein: Replication Enhancement and Protein Interactions

2005 ◽  
Vol 79 (15) ◽  
pp. 9885-9895 ◽  
Author(s):  
Sharon B. Settlage ◽  
Renee G. See ◽  
Linda Hanley-Bowdoin
Keyword(s):  
Viral Replication ◽  
Protein Interactions ◽  
Nuclear Antigen ◽  
Rolling Circle Replication ◽  
Rolling Circle ◽  
Hydrophobic Residues ◽  
Differentiated Cells ◽  
Leaf Curl Virus ◽  
The Impact ◽  
Proliferating Cell

ABSTRACT Most dicot-infecting geminiviruses encode a replication enhancer protein (C3, AL3, or REn) that is required for optimal replication of their small, single-stranded DNA genomes. C3 interacts with C1, the essential viral replication protein that initiates rolling circle replication. C3 also homo-oligomerizes and interacts with at least two host-encoded proteins, proliferating cell nuclear antigen (PCNA) and the retinoblastoma-related protein (pRBR). It has been proposed that protein interactions contribute to C3 function. Using the C3 protein of Tomato yellow leaf curl virus, we examined the impact of mutations to amino acids that are conserved across the C3 protein family on replication enhancement and protein interactions. Surprisingly, many of the mutations did not affect replication enhancement activity of C3 in tobacco protoplasts. Other mutations either enhanced or were detrimental to C3 replication activity. Analysis of mutated proteins in yeast two-hybrid assays indicated that mutations that inactivate C3 replication enhancement activity also reduce or inactivate C3 oligomerization and interaction with C1 and PCNA. In contrast, mutated C3 proteins impaired for pRBR binding are fully functional in replication assays. Hydrophobic residues in the middle of the C3 protein were implicated in C3 interaction with itself, C1, and PCNA, while polar resides at both the N and C termini of the protein are important for C3-pRBR interaction. These experiments established the importance of C3-C3, C3-C1, and C3-PCNA interactions in geminivirus replication. While C3-pRBR interaction is not required for viral replication in cycling cells, it may play a role during infection of differentiated cells in intact plants.

scholarly journals Topologically associating domain boundaries are enriched in early firing origins and restrict replication fork progression

2020 ◽  
Author(s):  
Emilia Puig Lombardi ◽  
Madalena Tarsounas
Keyword(s):  
Binding Sites ◽  
Replication Fork ◽  
Replication Timing ◽  
Replication Initiation ◽  
Ctcf Binding ◽  
Origin Firing ◽  
Replication Fork Progression ◽  
Fork Stalling ◽  
Genomic Regions ◽  
The Impact

ABSTRACTTopologically associating domains (TADs) are units of the genome architecture defined by binding sites for the CTCF transcription factor and cohesin-mediated loop extrusion. Genomic regions containing DNA replication initiation sites have been mapped in the proximity of TAD boundaries. However, the factors that determine this positioning have not been identified. Moreover, the impact of TADs on the directionality of replication fork progression remains unknown. Here we use EdU-seq technology to map origin firing sites at 10 kb resolution and to monitor replication fork progression after restart from hydroxyurea arrest. We show that origins firing in early/mid S-phase within TAD boundaries map to two distinct peaks flanking the centre of the boundary, which is occupied by CTCF and cohesin. When transcription is inhibited chemically or deregulated by oncogene overexpression, replication origins become repositioned to the centre of the TAD. Furthermore, we demonstrate the strikingly asymmetric fork progression initiating from origins located within TAD boundaries. Divergent CTCF binding sites and neighbouring TADs with different replication timing (RT) cause fork stalling in regions external to the TAD. Thus, our work assigns for the first time a role to transcription within TAD boundaries in promoting replication origin firing and demonstrates how genomic regions adjacent to the TAD boundaries could restrict replication progression.

scholarly journals The CMG helicase bypasses DNA protein cross-links to facilitate their repair

2018 ◽  
Author(s):  
Justin L. Sparks ◽  
Alan O. Gao ◽  
Markus Räschle ◽  
Nicolai B. Larsen ◽  
Matthias Mann ◽  
...  
Keyword(s):  
Replication Fork ◽  
Dna Helicase ◽  
Genome Integrity ◽  
Cross Link ◽  
Replication Fork Progression ◽  
Egg Extracts ◽  
Cross Links ◽  
Leading Strand ◽  
Nucleoprotein Complexes ◽  
Lagging Strand

SummaryCovalent and non-covalent nucleoprotein complexes impede replication fork progression and thereby threaten genome integrity. UsingXenopus laevisegg extracts, we previously showed that when a replication fork encounters a covalent DNA-protein cross-link (DPC) on the leading strand template, the DPC is degraded to a short peptide, allowing its bypass by translesion synthesis polymerases. Strikingly, we show here that when DPC proteolysis is blocked, the replicative DNA helicase (CMG), which travels on the leading strand template, still bypasses the intact DPC. The DNA helicase RTEL1 facilitates bypass, apparently by translocating along the lagging strand template and generating single-stranded DNA downstream of the DPC. Remarkably, RTEL1 is required for efficient DPC proteolysis, suggesting that CMG bypass of a DPC normally precedes its proteolysis. RTEL1 also promotes fork progression past non-covalent protein-DNA complexes. Our data suggest a unified model for the replisome’s response to nucleoprotein barriers.

scholarly journals Single-molecule imaging reveals control of parental histone recycling by free histones during DNA replication

2019 ◽  
Author(s):  
Dominika T. Gruszka ◽  
Sherry Xie ◽  
Hiroshi Kimura ◽  
Hasan Yardimci
Keyword(s):  
Cell Division ◽  
Xenopus Laevis ◽  
Single Molecule ◽  
Replication Fork ◽  
Direct Evidence ◽  
Single Molecule Imaging ◽  
Epigenetic Memory ◽  
Close Proximity ◽  
Egg Extracts ◽  
Fork Stalling

SUMMARYFaithful replication of chromatin domains during cell division is fundamental to eukaryotic development. During replication, nucleosomes are disrupted ahead of the replication fork, followed by their rapid reassembly on daughter strands from the pool of recycled parental and newly synthesized histones. Here, we use single-molecule imaging and replication assays in Xenopus laevis egg extracts to determine the outcome of replication fork encounters with nucleosomes. Contrary to current models, the majority of parental histones are evicted from the DNA, with histone recycling, nucleosome sliding and replication fork stalling also occurring but at lower frequencies. The anticipated local histone transfer only becomes dominant upon depletion of free histones from extracts. Our studies provide the first direct evidence that parental histones remain in close proximity to their original locus during recycling and reveal that provision of excess histones results in impaired histone recycling, which has the potential to affect epigenetic memory.

scholarly journals Mitotic CDK promotes replisome disassembly, fork breakage, and complex DNA rearrangements

2018 ◽  
Author(s):  
Lin Deng ◽  
R. Alex. Wu ◽  
Olga V. Kochenova ◽  
David Pellman ◽  
Johannes C. Walter
Keyword(s):  
Dna Replication ◽  
Replication Fork ◽  
Chromosomal Rearrangements ◽  
Cyclin B1 ◽  
Template Switching ◽  
List Type ◽  
End Joining ◽  
Dna Rearrangements ◽  
Egg Extracts ◽  
The Impact

SUMMARYDNA replication errors generate complex chromosomal rearrangements and thereby contribute to tumorigenesis and other human diseases. Although the events that trigger these errors are not well understood, one candidate is mitotic entry before the completion of DNA replication. To address the impact of mitosis on DNA replication, we employed Xenopus egg extracts. When mitotic CDK (Cyclin B1-CDK1) is used to drive these extracts into mitosis, the E3 ubiquitin ligase TRAIP promotes ubiquitylation of the replicative CMG (CDC45/MCM2–7/GINS) helicase at stalled forks and at forks that have completed DNA synthesis. In both cases, ubiquitylation is followed by CMG extraction from chromatin by the CDC48/p97 ATPase. At stalled forks, CMG removal results in fork breakage and complex end joining events involving deletions and template-switching. Our results identify TRAIP-dependent replisome disassembly as a novel trigger of replication fork collapse and propose it underlies complex DNA rearrangements in mitosis.HIGHLIGHTSTRAIP-dependent MCM7 ubiquitylation removes all CMGs from chromatin in mitosisCMG unloading from stalled forks causes replication fork breakageReplication fork breakage in mitosis causes complex rearrangementsNew model of replication fork collapse

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