scholarly journals Esc2 and Sgs1 Act in Functionally Distinct Branches of the Homologous Recombination Repair Pathway inSaccharomyces cerevisiae

2009 ◽  
Vol 20 (6) ◽  
pp. 1683-1694 ◽  
Author(s):  
Hocine W. Mankouri ◽  
Hien-Ping Ngo ◽  
Ian D. Hickson
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Structural Similarity ◽  
S Phase ◽  
Homologous Recombination Repair ◽  
Dna Damage Checkpoint ◽  
Checkpoint Signaling ◽  
Checkpoint Response ◽  
Recombination Repair ◽  
Anemia Group

Esc2 is a member of the RENi family of SUMO-like domain proteins and is implicated in gene silencing in Saccharomyces cerevisiae. Here, we identify a dual role for Esc2 during S-phase in mediating both intra-S-phase DNA damage checkpoint signaling and preventing the accumulation of Rad51-dependent homologous recombination repair (HRR) intermediates. These roles are qualitatively similar to those of Sgs1, the yeast ortholog of the human Bloom's syndrome protein, BLM. However, whereas mutation of either ESC2 or SGS1 leads to the accumulation of unprocessed HRR intermediates in the presence of MMS, the accumulation of these structures in esc2 (but not sgs1) mutants is entirely dependent on Mph1, a protein that shows structural similarity to the Fanconi anemia group M protein (FANCM). In the absence of both Esc2 and Sgs1, the intra-S-phase DNA damage checkpoint response is compromised after exposure to MMS, and sgs1esc2 cells attempt to undergo mitosis with unprocessed HRR intermediates. We propose a model whereby Esc2 acts in an Mph1-dependent process, separately from Sgs1, to influence the repair/tolerance of MMS-induced lesions during S-phase.

scholarly journals The Role of MRN in the S-Phase DNA Damage Checkpoint Is Independent of Its Ctp1-dependent Roles in Double-Strand Break Repair and Checkpoint Signaling

2009 ◽  
Vol 20 (7) ◽  
pp. 2096-2107 ◽  
Author(s):  
Mary E. Porter-Goff ◽  
Nicholas Rhind
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Strand Break ◽  
Double Strand Break ◽  
S Phase ◽  
Double Strand Break Repair ◽  
Dna Damage Checkpoint ◽  
Checkpoint Signaling ◽  
Break Repair ◽  
S Phase Checkpoint

The Mre11-Rad50-Nbs1 (MRN) complex has many biological functions: processing of double-strand breaks in meiosis, homologous recombination, telomere maintenance, S-phase checkpoint, and genome stability during replication. In the S-phase DNA damage checkpoint, MRN acts both in activation of checkpoint signaling and downstream of the checkpoint kinases to slow DNA replication. Mechanistically, MRN, along with its cofactor Ctp1, is involved in 5′ resection to create single-stranded DNA that is required for both signaling and homologous recombination. However, it is unclear whether resection is essential for all of the cellular functions of MRN. To dissect the various roles of MRN, we performed a structure–function analysis of nuclease dead alleles and potential separation-of-function alleles analogous to those found in the human disease ataxia telangiectasia-like disorder, which is caused by mutations in Mre11. We find that several alleles of rad32 (the fission yeast homologue of mre11), along with ctp1Δ, are defective in double-strand break repair and most other functions of the complex, but they maintain an intact S phase DNA damage checkpoint. Thus, the MRN S-phase checkpoint role is separate from its Ctp1- and resection-dependent role in double-strand break repair. This observation leads us to conclude that other functions of MRN, possibly its role in replication fork metabolism, are required for S-phase DNA damage checkpoint function.

scholarly journals Shu Proteins Promote the Formation of Homologous Recombination Intermediates That Are Processed by Sgs1-Rmi1-Top3

2007 ◽  
Vol 18 (10) ◽  
pp. 4062-4073 ◽  
Author(s):  
Hocine W. Mankouri ◽  
Hien-Ping Ngo ◽  
Ian D. Hickson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Homologous Recombination ◽  
S Phase ◽  
Specific Role ◽  
Homologous Recombination Repair ◽  
Recombination Repair ◽  
Mutant Phenotypes ◽  
Precise Role

CSM2, PSY3, SHU1, and SHU2 (collectively referred to as the SHU genes) were identified in Saccharomyces cerevisiae as four genes in the same epistasis group that suppress various sgs1 and top3 mutant phenotypes when mutated. Although the SHU genes have been implicated in homologous recombination repair (HRR), their precise role(s) within this pathway remains poorly understood. Here, we have identified a specific role for the Shu proteins in a Rad51/Rad54-dependent HRR pathway(s) to repair MMS-induced lesions during S-phase. We show that, although mutation of RAD51 or RAD54 prevented the formation of MMS-induced HRR intermediates (X-molecules) arising during replication in sgs1 cells, mutation of SHU genes attenuated the level of these structures. Similar findings were also observed in shu1 cells in which Rmi1 or Top3 function was impaired. We propose a model in which the Shu proteins act in HRR to promote the formation of HRR intermediates that are processed by the Sgs1-Rmi1-Top3 complex.

scholarly journals Biphasic recruitment of TRF2 to DNA damage sites promotes non-sister chromatid homologous recombination repair

2018 ◽  
Vol 131 (23) ◽  
pp. jcs219311 ◽  
Author(s):  
Xiangduo Kong ◽  
Gladys Mae Saquilabon Cruz ◽  
Sally Loyal Trinh ◽  
Xu-Dong Zhu ◽  
Michael W. Berns ◽  
...  
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Sister Chromatid ◽  
Homologous Recombination Repair ◽  
Recombination Repair

scholarly journals PARP1-dependent recruitment of the FBXL10-RNF68-RNF2 ubiquitin ligase to sites of DNA damage controls H2A.Z loading

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Gergely Rona ◽  
Domenico Roberti ◽  
Yandong Yin ◽  
Julia K Pagan ◽  
Harrison Homer ◽  
...  
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Ubiquitin Ligase ◽  
Transcriptional Repression ◽  
Genotoxic Stress ◽  
Strand Break ◽  
Homologous Recombination Repair ◽  
Dependent Manner ◽  
Ubiquitin Ligase Complex ◽  
Recombination Repair

The mammalian FBXL10-RNF68-RNF2 ubiquitin ligase complex (FRRUC) mono-ubiquitylates H2A at Lys119 to repress transcription in unstressed cells. We found that the FRRUC is rapidly and transiently recruited to sites of DNA damage in a PARP1- and TIMELESS-dependent manner to promote mono-ubiquitylation of H2A at Lys119, a local decrease of H2A levels, and an increase of H2A.Z incorporation. Both the FRRUC and H2A.Z promote transcriptional repression, double strand break signaling, and homologous recombination repair (HRR). All these events require both the presence and activity of the FRRUC. Moreover, the FRRUC and its activity are required for the proper recruitment of BMI1-RNF2 and MEL18-RNF2, two other ubiquitin ligases that mono-ubiquitylate Lys119 in H2A upon genotoxic stress. Notably, whereas H2A.Z is not required for H2A mono-ubiquitylation, impairment of the latter results in the inhibition of H2A.Z incorporation. We propose that the recruitment of the FRRUC represents an early and critical regulatory step in HRR.

scholarly journals Proton Irradiation Increases the Necessity for Homologous Recombination Repair Along with the Indispensability of Non-Homologous End Joining

Cells ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 889 ◽  
Author(s):  
Klaudia Szymonowicz ◽  
Adam Krysztofiak ◽  
Jansje van der Linden ◽  
Ajvar Kern ◽  
Simon Deycmar ◽  
...  
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Proton Irradiation ◽  
Negative Impact ◽  
Particle Therapy ◽  
Homologous Recombination Repair ◽  
End Joining ◽  
X Ray ◽  
Recombination Repair ◽  
Non Homologous End Joining

Technical improvements in clinical radiotherapy for maximizing cytotoxicity to the tumor while limiting negative impact on co-irradiated healthy tissues include the increasing use of particle therapy (e.g., proton therapy) worldwide. Yet potential differences in the biology of DNA damage induction and repair between irradiation with X-ray photons and protons remain elusive. We compared the differences in DNA double strand break (DSB) repair and survival of cells compromised in non-homologous end joining (NHEJ), homologous recombination repair (HRR) or both, after irradiation with an equal dose of X-ray photons, entrance plateau (EP) protons, and mid spread-out Bragg peak (SOBP) protons. We used super-resolution microscopy to investigate potential differences in spatial distribution of DNA damage foci upon irradiation. While DNA damage foci were equally distributed throughout the nucleus after X-ray photon irradiation, we observed more clustered DNA damage foci upon proton irradiation. Furthermore, deficiency in essential NHEJ proteins delayed DNA repair kinetics and sensitized cells to both, X-ray photon and proton irradiation, whereas deficiency in HRR proteins sensitized cells only to proton irradiation. We assume that NHEJ is indispensable for processing DNA DSB independent of the irradiation source, whereas the importance of HRR rises with increasing energy of applied irradiation.

scholarly journals Undamaged DNA Transmits and Enhances DNA Damage Checkpoint Signals in Early Embryos

2007 ◽  
Vol 27 (19) ◽  
pp. 6852-6862 ◽  
Author(s):  
Aimin Peng ◽  
Andrea L. Lewellyn ◽  
James L. Maller
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Nuclear Dna ◽  
Cell Cycle Checkpoint ◽  
Dna Damage Checkpoint ◽  
Checkpoint Signaling ◽  
Checkpoint Response ◽  
Egg Extracts ◽  
Cycle Checkpoint ◽  
Damaged Dna

ABSTRACT In Xenopus laevis embryos, the midblastula transition (MBT) at the 12th cell division marks initiation of critical developmental events, including zygotic transcription and the abrupt inclusion of gap phases into the cell cycle. Interestingly, although an ionizing radiation-induced checkpoint response is absent in pre-MBT embryos, introduction of a threshold amount of undamaged plasmid or sperm DNA allows a DNA damage checkpoint response to be activated. We show here that undamaged threshold DNA directly participates in checkpoint signaling, as judged by several dynamic changes, including H2AX phosphorylation, ATM phosphorylation and loading onto chromatin, and Chk1/Chk2 phosphorylation and release from nuclear DNA. These responses on physically separate threshold DNA require γ-H2AX and are triggered by an ATM-dependent soluble signal initiated by damaged DNA. The signal persists in egg extracts even after damaged DNA is removed from the system, indicating that the absence of damaged DNA is not sufficient to end the checkpoint response. The results identify a novel mechanism by which undamaged DNA enhances checkpoint signaling and provide an example of how the transition to cell cycle checkpoint activation during development is accomplished by maternally programmed increases in the DNA-to-cytoplasm ratio.

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