scholarly journals Akt: A Double-Edged Sword in Cell Proliferation and Genome Stability

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Naihan Xu ◽  
Yuanzhi Lao ◽  
Yaou Zhang ◽  
David A. Gillespie
Keyword(s):  
Genome Stability ◽  
Strand Break ◽  
Nonhomologous End Joining ◽  
Dependent Manner ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Cell Behaviour ◽  
Cell Cycles ◽  
Strand Breaks ◽  
Recombination Repair

The Akt family of serine/threonine protein kinases are key regulators of multiple aspects of cell behaviour, including proliferation, survival, metabolism, and tumorigenesis. Growth-factor-activated Akt signalling promotes progression through normal, unperturbed cell cycles by acting on diverse downstream factors involved in controlling the G1/S and G2/M transitions. Remarkably, several recent studies have also implicated Akt in modulating DNA damage responses and genome stability. High Akt activity can suppress ATR/Chk1 signalling and homologous recombination repair (HRR) via direct phosphorylation of Chk1 or TopBP1 or, indirectly, by inhibiting recruitment of double-strand break (DSB) resection factors, such as RPA, Brca1, and Rad51, to sites of damage. Loss of checkpoint and/or HRR proficiency is therefore a potential cause of genomic instability in tumor cells with high Akt. Conversely, Akt is activated by DNA double-strand breaks (DSBs) in a DNA-PK- or ATM/ATR-dependent manner and in some circumstances can contribute to radioresistance by stimulating DNA repair by nonhomologous end joining (NHEJ). Akt therefore modifies both the response to and repair of genotoxic damage in complex ways that are likely to have important consequences for the therapy of tumors with deregulation of the PI3K-Akt-PTEN pathway.

scholarly journals Parp3 promotes long-range end joining in murine cells

2018 ◽  
Vol 115 (40) ◽  
pp. 10076-10081 ◽  
Author(s):  
Jacob V. Layer ◽  
J. Patrick Cleary ◽  
Alexander J. Brown ◽  
Kristen E. Stevenson ◽  
Sara N. Morrow ◽  
...  
Keyword(s):  
Chromosomal Rearrangements ◽  
Embryonic Stem ◽  
Cell Types ◽  
Strand Break ◽  
Nonhomologous End Joining ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Class Switch

Chromosomal rearrangements, including translocations, are early and essential events in the formation of many tumors. Previous studies that defined the genetic requirements for rearrangement formation have identified differences between murine and human cells, most notably in the role of classic and alternative nonhomologous end-joining (NHEJ) factors. We reported that poly(ADP)ribose polymerase 3 (PARP3) promotes chromosomal rearrangements induced by endonucleases in multiple human cell types. We show here that in contrast to classic (c-NHEJ) factors, Parp3 also promotes rearrangements in murine cells, including translocations in murine embryonic stem cells (mESCs), class–switch recombination in primary B cells, and inversions in tail fibroblasts that generateEml4–Alkfusions. In mESCs, Parp3-deficient cells had shorter deletion lengths at translocation junctions. This was corroborated using next-generation sequencing ofEml4–Alkjunctions in tail fibroblasts and is consistent with a role for Parp3 in promoting the processing of DNA double-strand breaks. We confirmed a previous report that Parp1 also promotes rearrangement formation. In contrast with Parp3, rearrangement junctions in the absence of Parp1 had longer deletion lengths, suggesting that Parp1 may suppress double-strand break processing. Together, these data indicate that Parp3 and Parp1 promote rearrangements with distinct phenotypes.

scholarly journals Structural snapshots of human DNA polymerase μ engaged on a DNA double-strand break

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Andrea M. Kaminski ◽  
John M. Pryor ◽  
Dale A. Ramsden ◽  
Thomas A. Kunkel ◽  
Lars C. Pedersen ◽  
...  
Keyword(s):  
Chromosomal Rearrangements ◽  
Strand Break ◽  
Nonhomologous End Joining ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Template Strand ◽  
Single Strand Breaks ◽  
Dna Double Strand Break ◽  
Break Site

Abstract Genomic integrity is threatened by cytotoxic DNA double-strand breaks (DSBs), which must be resolved efficiently to prevent sequence loss, chromosomal rearrangements/translocations, or cell death. Polymerase μ (Polμ) participates in DSB repair via the nonhomologous end-joining (NHEJ) pathway, by filling small sequence gaps in broken ends to create substrates ultimately ligatable by DNA Ligase IV. Here we present structures of human Polμ engaging a DSB substrate. Synapsis is mediated solely by Polμ, facilitated by single-nucleotide homology at the break site, wherein both ends of the discontinuous template strand are stabilized by a hydrogen bonding network. The active site in the quaternary Pol μ complex is poised for catalysis and nucleotide incoporation proceeds in crystallo. These structures demonstrate that Polμ may address complementary DSB substrates during NHEJ in a manner indistinguishable from single-strand breaks.

scholarly journals Ubiquitin-Specific-Processing Protease 47, A Novel 53BP1 regulator

2021 ◽  
Author(s):  
Doraid T. Sadideen ◽  
Baowei Chen ◽  
Manal Basili ◽  
Montaser Shaheen
Keyword(s):  
Strand Break ◽  
Dependent Manner ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Class Switch ◽  
Dna Double Strand Break ◽  
Radiation Induced ◽  
Non Homologous End Joining ◽  
Processing Protease

AbstractDNA double strand breaks (DSBs) are repair by homology-based repair or non-homologous end joining and multiple sub-pathways exist. 53BP1 is a key DNA double strand break repair protein that regulates repair pathway choice. It is key for joining DSBs during immunoglobulin heavy chain class switch recombination. Here we identify USP47 as a deubiquitylase that associates with and regulates 53BP1 function. USP47 loss results in 53BP1 instability in proteasome dependent manner, and defective 53BP1 ionizing radiation induced foci (IRIF). USP47 catalytic activity is required for maintaining 53BP1 protein level. Similar to 53BP1, USP47 depletion results in sensitivity to DNA DSB inducing agents and defective immunoglobulin CSR. Our findings establish a function for USP47 in DNA DSB repair at least partially through 53BP1.

Repair of DNA Double-Strand Breaks by the Nonhomologous End Joining Pathway

2021 ◽  
Vol 90 (1) ◽  
Author(s):  
Benjamin M. Stinson ◽  
Joseph J. Loparo
Keyword(s):  
Genome Stability ◽  
Double Strand Breaks ◽  
Nonhomologous End Joining ◽  
Annual Review ◽  
Publication Date ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Break Site ◽  
Dna Ends

DNA double-strand breaks pose a serious threat to genome stability. In vertebrates, these breaks are predominantly repaired by nonhomologous end joining (NHEJ), which pairs DNA ends in a multiprotein synaptic complex to promote their direct ligation. NHEJ is a highly versatile pathway that uses an array of processing enzymes to modify damaged DNA ends and enable their ligation. The mechanisms of end synapsis and end processing have important implications for genome stability. Rapid and stable synapsis is necessary to limit chromosome translocations that result from the mispairing of DNA ends. Furthermore, end processing must be tightly regulated to minimize mutations at the break site. Here, we review our current mechanistic understanding of vertebrate NHEJ, with a particular focus on end synapsis and processing. Expected final online publication date for the Annual Review of Biochemistry, Volume 90 is June 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals To Join or Not to Join: Decision Points Along the Pathway to Double-Strand Break Repair vs. Chromosome End Protection

2021 ◽  
Vol 9 ◽  
Author(s):  
Stephanie M. Ackerson ◽  
Carlan Romney ◽  
P. Logan Schuck ◽  
Jason A. Stewart
Keyword(s):  
Genome Stability ◽  
Strand Break ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Strand Breaks ◽  
Decision Points ◽  
Chromosome Fusions ◽  
Non Homologous End Joining ◽  
Dna Ends

The regulation of DNA double-strand breaks (DSBs) and telomeres are diametrically opposed in the cell. DSBs are considered one of the most deleterious forms of DNA damage and must be quickly recognized and repaired. Telomeres, on the other hand, are specialized, stable DNA ends that must be protected from recognition as DSBs to inhibit unwanted chromosome fusions. Decisions to join DNA ends, or not, are therefore critical to genome stability. Yet, the processing of telomeres and DSBs share many commonalities. Accordingly, key decision points are used to shift DNA ends toward DSB repair vs. end protection. Additionally, DSBs can be repaired by two major pathways, namely homologous recombination (HR) and non-homologous end joining (NHEJ). The choice of which repair pathway is employed is also dictated by a series of decision points that shift the break toward HR or NHEJ. In this review, we will focus on these decision points and the mechanisms that dictate end protection vs. DSB repair and DSB repair choice.

scholarly journals Meiotic DNA repair in the nucleolus employs a non-homologous end joining mechanism

2019 ◽  
Author(s):  
Jason Sims ◽  
Gregory P. Copenhaver ◽  
Peter Schlögelhofer
Keyword(s):  
Genome Stability ◽  
Dependent Manner ◽  
Dna Double Strand Breaks ◽  
Dna Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Meiotic Dsbs ◽  
Dna Elements ◽  
Highly Repetitive Dna ◽  
Non Homologous End Joining

AbstractRibosomal RNA genes are arranged in large arrays with hundreds of rDNA units in tandem. These highly repetitive DNA elements pose a risk to genome stability since they can undergo non-allelic exchanges. During meiosis DNA double strand breaks (DSBs) are induced as part of the regular program to generate gametes. Meiotic DSBs initiate homologous recombination (HR) which subsequently ensures genetic exchange and chromosome disjunction.In Arabidopsis thaliana we demonstrate that all 45S rDNA arrays become transcriptionally active and are recruited into the nucleolus early in meiosis. This shields the rDNA from acquiring canonical meiotic chromatin modifications, meiotic cohesin and meiosis-specific DSBs. DNA breaks within the rDNA arrays are repaired in a RAD51-independent, but LIG4-dependent manner, establishing that it is non-homologous end joining (NHEJ) that maintains rDNA integrity during meiosis. Utilizing ectopically integrated rDNA repeats we validate our findings and demonstrate that the rDNA constitutes a HR-refractory genome environment.

scholarly journals Ligase I and ligase III mediate the DNA double-strand break ligation in alternative end-joining

2016 ◽  
Vol 113 (5) ◽  
pp. 1256-1260 ◽  
Author(s):  
Guangqing Lu ◽  
Jinzhi Duan ◽  
Sheng Shu ◽  
Xuxiang Wang ◽  
Linlin Gao ◽  
...  
Keyword(s):  
Strand Break ◽  
Chromosome Translocation ◽  
Nonhomologous End Joining ◽  
Dna Ligase ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Dna Double Strand Break ◽  
Alternative End Joining ◽  
Class Switching Recombination

In eukaryotes, DNA double-strand breaks (DSBs), one of the most harmful types of DNA damage, are repaired by homologous repair (HR) and nonhomologous end-joining (NHEJ). Surprisingly, in cells deficient for core classic NHEJ factors such as DNA ligase IV (Lig4), substantial end-joining activities have been observed in various situations, suggesting the existence of alternative end-joining (A-EJ) activities. Several putative A-EJ factors have been proposed, although results are mostly controversial. By using a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system, we generated mouse CH12F3 cell lines in which, in addition to Lig4, either Lig1 or nuclear Lig3, representing the cells containing a single DNA ligase (Lig3 or Lig1, respectively) in their nucleus, was completely ablated. Surprisingly, we found that both Lig1- and Lig3-containing complexes could efficiently catalyze A-EJ for class switching recombination (CSR) in the IgH locus and chromosomal deletions between DSBs generated by CRISPR/Cas9 in cis-chromosomes. However, only deletion of nuclear Lig3, but not Lig1, could significantly reduce the interchromosomal translocations in Lig4−/− cells, suggesting the unique role of Lig3 in catalyzing chromosome translocation. Additional sequence analysis of chromosome translocation junction microhomology revealed the specificity of different ligase-containing complexes. The data suggested the existence of multiple DNA ligase-containing complexes in A-EJ.

scholarly journals XRCC4 and XLF form long helical protein filaments suitable for DNA end protection and alignment to facilitate DNA double strand break repair

2013 ◽  
Vol 91 (1) ◽  
pp. 31-41 ◽  
Author(s):  
Brandi L. Mahaney ◽  
Michal Hammel ◽  
Katheryn Meek ◽  
John A. Tainer ◽  
Susan P. Lees-Miller
Keyword(s):  
Strand Break ◽  
Nonhomologous End Joining ◽  
Scaffolding Protein ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Dna Double Strand Break ◽  
Helical Protein ◽  
Gene 4 ◽  
Dna Ends

DNA double strand breaks (DSBs), induced by ionizing radiation (IR) and endogenous stress including replication failure, are the most cytotoxic form of DNA damage. In human cells, most IR-induced DSBs are repaired by the nonhomologous end joining (NHEJ) pathway. One of the most critical steps in NHEJ is ligation of DNA ends by DNA ligase IV (LIG4), which interacts with, and is stabilized by, the scaffolding protein X-ray cross-complementing gene 4 (XRCC4). XRCC4 also interacts with XRCC4-like factor (XLF, also called Cernunnos); yet, XLF has been one of the least mechanistically understood proteins and precisely how XLF functions in NHEJ has been enigmatic. Here, we examine current combined structural and mutational findings that uncover integrated functions of XRCC4 and XLF and reveal their interactions to form long, helical protein filaments suitable to protect and align DSB ends. XLF–XRCC4 provides a global structural scaffold for ligating DSBs without requiring long DNA ends, thus ensuring accurate and efficient ligation and repair. The assembly of these XRCC4–XLF filaments, providing both DNA end protection and alignment, may commit cells to NHEJ with general biological implications for NHEJ and DSB repair processes and their links to cancer predispositions and interventions.

scholarly journals Increased BUB1B/BUBR1 expression contributes to aberrant DNA repair activity leading to resistance to DNA-damaging agents

Oncogene ◽  
2021 ◽  
Author(s):  
Kazumasa Komura ◽  
Teruo Inamoto ◽  
Takuya Tsujino ◽  
Yusuke Matsui ◽  
Tsuyoshi Konuma ◽  
...  
Keyword(s):  
Dna Repair ◽  
Nonhomologous End Joining ◽  
Dependent Manner ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Dna Damaging Agents ◽  
Repair Activity ◽  
A Cell

AbstractThere has been accumulating evidence for the clinical benefit of chemoradiation therapy (CRT), whereas mechanisms in CRT-recurrent clones derived from the primary tumor are still elusive. Herein, we identified an aberrant BUB1B/BUBR1 expression in CRT-recurrent clones in bladder cancer (BC) by comprehensive proteomic analysis. CRT-recurrent BC cells exhibited a cell-cycle-independent upregulation of BUB1B/BUBR1 expression rendering an enhanced DNA repair activity in response to DNA double-strand breaks (DSBs). With DNA repair analyses employing the CRISPR/cas9 system, we revealed that cells with aberrant BUB1B/BUBR1 expression dominantly exploit mutagenic nonhomologous end joining (NHEJ). We further found that phosphorylated ATM interacts with BUB1B/BUBR1 after ionizing radiation (IR) treatment, and the resistance to DSBs by increased BUB1B/BUBR1 depends on the functional ATM. In vivo, tumor growth of CRT-resistant T24R cells was abrogated by ATM inhibition using AZD0156. A dataset analysis identified FOXM1 as a putative BUB1B/BUBR1-targeting transcription factor causing its increased expression. These data collectively suggest a redundant role of BUB1B/BUBR1 underlying mutagenic NHEJ in an ATM-dependent manner, aside from the canonical activity of BUB1B/BUBR1 on the G2/M checkpoint, and offer novel clues to overcome CRT resistance.

scholarly journals Evolutionary and Comparative Analysis of Bacterial Nonhomologous End Joining Repair

2020 ◽  
Vol 12 (12) ◽  
pp. 2450-2466
Author(s):  
Mohak Sharda ◽  
Anjana Badrinarayanan ◽  
Aswin Sai Narain Seshasayee
Keyword(s):  
Genome Stability ◽  
Double Strand Breaks ◽  
Nonhomologous End Joining ◽  
Ancestral Reconstruction ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Domains Of Life ◽  
History Of ◽  
Two Kingdoms

Abstract DNA double-strand breaks (DSBs) are a threat to genome stability. In all domains of life, DSBs are faithfully fixed via homologous recombination. Recombination requires the presence of an uncut copy of duplex DNA which is used as a template for repair. Alternatively, in the absence of a template, cells utilize error-prone nonhomologous end joining (NHEJ). Although ubiquitously found in eukaryotes, NHEJ is not universally present in bacteria. It is unclear as to why many prokaryotes lack this pathway. Toward understanding what could have led to the current distribution of bacterial NHEJ, we carried out comparative genomics and phylogenetic analysis across ∼6,000 genomes. Our results show that this pathway is sporadically distributed across the phylogeny. Ancestral reconstruction further suggests that NHEJ was absent in the eubacterial ancestor and can be acquired via specific routes. Integrating NHEJ occurrence data for archaea, we also find evidence for extensive horizontal exchange of NHEJ genes between the two kingdoms as well as across bacterial clades. The pattern of occurrence in bacteria is consistent with correlated evolution of NHEJ with key genome characteristics of genome size and growth rate; NHEJ presence is associated with large genome sizes and/or slow growth rates, with the former being the dominant correlate. Given the central role these traits play in determining the ability to carry out recombination, it is possible that the evolutionary history of bacterial NHEJ may have been shaped by requirement for efficient DSB repair.

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