scholarly journals RPA Mediates Recruitment of MRX to Forks and Double-Strand Breaks to Hold Sister Chromatids Together

2016 ◽  
Vol 64 (5) ◽  
pp. 951-966 ◽  
Author(s):  
Andrew Seeber ◽  
Anna Maria Hegnauer ◽  
Nicole Hustedt ◽  
Ishan Deshpande ◽  
Jérôme Poli ◽  
...  
Keyword(s):  
Double Strand Breaks ◽  
Strand Breaks ◽  
Sister Chromatids

scholarly journals Double-strand breaks are not the main cause of spontaneous sister chromatid exchange in wild-type yeast cells

2017 ◽  
Author(s):  
Clémence Claussin ◽  
David Porubský ◽  
Diana C.J. Spierings ◽  
Nancy Halsema ◽  
Stefan Rentas ◽  
...  
Keyword(s):  
Sister Chromatid ◽  
Sister Chromatid Exchange ◽  
Genome Instability ◽  
Single Cells ◽  
Double Strand Breaks ◽  
Yeast Cells ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Template Strand ◽  
Sister Chromatids

SummaryHomologous recombination involving sister chromatids is the most accurate, and thus most frequently used, form of recombination-mediated DNA repair. Despite its importance, sister chromatid recombination is not easily studied because it does not result in a change in DNA sequence, making recombination between sister chromatids difficult to detect. We have previously developed a novel DNA template strand sequencing technique, called Strand-seq, that can be used to map sister chromatid exchange (SCE) events genome-wide in single cells. An increase in the rate of SCE is an indicator of elevated recombination activity and of genome instability, which is a hallmark of cancer. In this study, we have adapted Strand-seq to detect SCE in the yeast Saccharomyces cerevisiae. Contrary to what is commonly thought, we find that most spontaneous SCE events are not due to the repair of DNA double-strand breaks.

scholarly journals Distinctive nuclear zone for RAD51-mediated homologous recombinational DNA repair

2021 ◽  
Author(s):  
Yasunori Horikoshi ◽  
Hiroki Shima ◽  
Wataru Kobayashi ◽  
Jiying Sun ◽  
Volker J Schmid ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Nuclear Architecture ◽  
Super Resolution ◽  
Double Strand Breaks ◽  
Genome Integrity ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Sister Chromatids ◽  
Super Resolution Microscopy ◽  
Damaged Dna

Genome-based functions are inseparable from the dynamic higher-order architecture of the cell nucleus. In this context, the repair of DNA damage is coordinated by precise spatiotemporal controls that target and regulate the repair machinery required to maintain genome integrity. However, the mechanisms that pair damaged DNA with intact template for repair by homologous recombination (HR) without illegitimate recombination remain unclear. This report highlights the intimate relationship between nuclear architecture and HR in mammalian cells. RAD51, the key recombinase of HR, forms spherical foci in S/G2 phases spontaneously. Using super-resolution microscopy, we show that following induction of DNA double-strand breaks RAD51 foci at damaged sites elongate to bridge between intact and damaged sister chromatids; this assembly occurs within bundle-shaped distinctive nuclear zones, requires interactions of RAD51 with various factors, and precedes ATP-dependent events involved the recombination of intact and damaged DNA. We observed a time-dependent transfer of single-stranded DNA overhangs, generated during HR, into such zones. Our observations suggest that RAD51-mediated homologous pairing during HR takes place within the distinctive nuclear zones to execute appropriate recombination.

scholarly journals Ensuring meiotic DNA break formation in the mouse pseudoautosomal region

2019 ◽  
Author(s):  
Laurent Acquaviva ◽  
Michiel Boekhout ◽  
Mehmet E. Karasu ◽  
Kevin Brick ◽  
Florencia Pratto ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Sex Chromosome ◽  
Double Strand Breaks ◽  
Pseudoautosomal Region ◽  
Homologous Segment ◽  
Strand Breaks ◽  
Sister Chromatids ◽  
Cis And Trans ◽  
Order Structures ◽  
Break Formation

Sex chromosomes in males share only a diminutive homologous segment, the pseudoautosomal region (PAR), wherein meiotic double-strand breaks (DSBs), pairing, and crossing over must occur for correct segregation. How cells ensure PAR recombination is unknown. Here we delineate cis-and trans-acting factors that control PAR ultrastructure and make the PAR the hottest area of DSB formation in the male mouse genome. Prior to DSB formation, PAR chromosome axes elongate, sister chromatids separate, and DSB-promoting factors hyperaccumulate. These phenomena are linked to mo-2 minisatellite arrays and require ANKRD31 protein. We propose that the repetitive PAR sequence confers unique chromatin and higher order structures crucial for DSB formation, X–Y pairing, and recombination. Our findings establish a mechanistic paradigm of mammalian sex chromosome segregation during spermatogenesis.

scholarly journals Role for the Silencing Protein Dot1 in Meiotic Checkpoint Control

2000 ◽  
Vol 11 (10) ◽  
pp. 3601-3615 ◽  
Author(s):  
Pedro A. San-Segundo ◽  
G. Shirleen Roeder
Keyword(s):  
Chromosome Segregation ◽  
Double Strand Breaks ◽  
Meiotic Cell ◽  
Checkpoint Control ◽  
Strand Breaks ◽  
Meiotic Progression ◽  
Chromosome Synapsis ◽  
Sister Chromatids ◽  
Surveillance Mechanism ◽  
Dependent Pathway

During the meiotic cell cycle, a surveillance mechanism called the “pachytene checkpoint” ensures proper chromosome segregation by preventing meiotic progression when recombination and chromosome synapsis are defective. The silencing protein Dot1 (also known as Pch1) is required for checkpoint-mediated pachytene arrest of thezip1 and dmc1 mutants ofSaccharomyces cerevisiae. In the absence ofDOT1, the zip1 and dmc1mutants inappropriately progress through meiosis, generating inviable meiotic products. Other components of the pachytene checkpoint include the nucleolar protein Pch2 and the heterochromatin component Sir2. Indot1, disruption of the checkpoint correlates with the loss of concentration of Pch2 and Sir2 in the nucleolus. In addition to its checkpoint function, Dot1 blocks the repair of meiotic double-strand breaks by a Rad54-dependent pathway of recombination between sister chromatids. In vegetative cells, mutation ofDOT1 results in delocalization of Sir3 from telomeres, accounting for the impaired telomeric silencing in dot1.

Repair pathway choice for double-strand breaks

2020 ◽  
Vol 64 (5) ◽  
pp. 765-777 ◽  
Author(s):  
Yixi Xu ◽  
Dongyi Xu
Keyword(s):  
Cell Cycle ◽  
Double Strand Breaks ◽  
Homologous Region ◽  
Gene Repair ◽  
Repair Pathway ◽  
Dna Double Strand Breaks ◽  
Environmental Radiation ◽  
Strand Breaks ◽  
Dna End Resection ◽  
End Resection

Abstract Deoxyribonucleic acid (DNA) is at a constant risk of damage from endogenous substances, environmental radiation, and chemical stressors. DNA double-strand breaks (DSBs) pose a significant threat to genomic integrity and cell survival. There are two major pathways for DSB repair: nonhomologous end-joining (NHEJ) and homologous recombination (HR). The extent of DNA end resection, which determines the length of the 3′ single-stranded DNA (ssDNA) overhang, is the primary factor that determines whether repair is carried out via NHEJ or HR. NHEJ, which does not require a 3′ ssDNA tail, occurs throughout the cell cycle. 53BP1 and the cofactors PTIP or RIF1-shieldin protect the broken DNA end, inhibit long-range end resection and thus promote NHEJ. In contrast, HR mainly occurs during the S/G2 phase and requires DNA end processing to create a 3′ tail that can invade a homologous region, ensuring faithful gene repair. BRCA1 and the cofactors CtIP, EXO1, BLM/DNA2, and the MRE11–RAD50–NBS1 (MRN) complex promote DNA end resection and thus HR. DNA resection is influenced by the cell cycle, the chromatin environment, and the complexity of the DNA end break. Herein, we summarize the key factors involved in repair pathway selection for DSBs and discuss recent related publications.

Bestimmung der DNA-Schädigung in vitro

2010 ◽  
Vol 49 (S 01) ◽  
pp. S64-S68
Author(s):  
E. Dikomey
Keyword(s):  
Dna Damage ◽  
Cell Lines ◽  
Chromosome Aberrations ◽  
Genetic Factors ◽  
Double Strand Breaks ◽  
Strand Breaks ◽  
Cell Inactivation ◽  
Repair Mechanisms ◽  
Break Repair

SummaryIonising irradiation acts primarily via induction of DNA damage, among which doublestrand breaks are the most important lesions. These lesions may lead to lethal chromosome aberrations, which are the main reason for cell inactivation. Double-strand breaks can be repaired by several different mechanisms. The regulation of these mechanisms appears be fairly different for normal and tumour cells. Among different cell lines capacity of doublestrand break repair varies by only few percents and is known to be determined mostly by genetic factors. Knowledge about doublestrand break repair mechanisms and their regulation is important for the optimal application of ionising irradiation in medicine.

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