scholarly journals Telomere-loop dynamics in chromosome end protection

2018 ◽  
Author(s):  
David Van Ly ◽  
Ronnie Ren Jie Low ◽  
Sonja Frölich ◽  
Tara K. Bartolec ◽  
Georgia R. Kafer ◽  
...  
Keyword(s):  
Super Resolution ◽  
G1 Arrest ◽  
Loop Formation ◽  
End Joining ◽  
Loop Dynamics ◽  
Non Homologous End Joining ◽  
Super Resolution Microscopy ◽  
Telomere Structure ◽  
Chromosome End Protection

SUMMARYWe used super-resolution microscopy to investigate the role of macromolecular telomere structure in chromosome end protection. In murine and human cells with reduced TRF2, we find that ATM-activation at chromosome ends occurs with a structural change from t-loops to linearized chromosome ends through t-loop unfolding. Comparably, we find Aurora B kinase regulates telomere linearity concurrent with ATM activation at telomeres during mitotic arrest. Using a separation of function allele, we find that the TRFH domain of TRF2 regulates t-loop formation while suppressing ATM activity. Notably, we demonstrate that telomere linearity and ATM activation occur separately from telomere fusion via non-homologous end-joining (NHEJ). Further, we show that linear DDR-positive telomeres can remain resistant to fusion, even during an extended G1-arrest when NHEJ is most active. Collectively, these results suggest t-loops act as conformational switches that regulate ATM activation at chromosome ends independent of mechanisms to suppress chromosome end fusion.

scholarly journals The role of RecQ helicases in non-homologous end-joining

2014 ◽  
Vol 49 (6) ◽  
pp. 463-472 ◽  
Author(s):  
Guido Keijzers ◽  
Scott Maynard ◽  
Raghavendra A. Shamanna ◽  
Lene Juel Rasmussen ◽  
Deborah L. Croteau ◽  
...  
Keyword(s):  
End Joining ◽  
Recq Helicases ◽  
Non Homologous End Joining

The role of the non-homologous end-joining pathway in lymphocyte development

2004 ◽  
Vol 200 (1) ◽  
pp. 115-131 ◽  
Author(s):  
Sean Rooney ◽  
Jayanta Chaudhuri ◽  
Frederick W. Alt
Keyword(s):  
Lymphocyte Development ◽  
End Joining ◽  
Non Homologous End Joining

scholarly journals Loss of Cdc13 causes genome instability by a deficiency in replication-dependent telomere capping

2019 ◽  
Author(s):  
Rachel E Langston ◽  
Dominic Palazzola ◽  
Erin Bonnell ◽  
Raymund J. Wellinger ◽  
Ted Weinert
Keyword(s):  
Homologous Recombination ◽  
Genome Stability ◽  
Genome Instability ◽  
Chromosome Instability ◽  
S Phase ◽  
Temperature Sensitive ◽  
End Joining ◽  
Telomere Capping ◽  
Non Homologous End Joining

AbstractIn budding yeast, Cdc13, Stn1, and Ten1 form a telomere binding heterotrimer dubbed CST. Here we investigate the role of Cdc13/CST in maintaining genome stability, using a Chr VII disome system that can generate recombinants, loss, and enigmatic unstable chromosomes. In cells expressing a temperature sensitive CDC13 allele, cdc13F684S, unstable chromosomes frequently arise due to problems in or near a telomere. Hence, when Cdc13 is defective, passage through S phase causes Exo1-dependent ssDNA and unstable chromosomes, which then are the source for whole chromosome instability events (e.g. recombinants, chromosome truncations, dicentrics, and/or loss). Specifically, genome instability arises from a defect in Cdc13’s replication-dependent telomere capping function, not Cdc13s putative post-replication telomere capping function. Furthermore, the unstable chromosomes form without involvement of homologous recombination nor non-homologous end joining. Our data suggest that a Cdc13/CST defect in semi-conservative replication near the telomere leads to ssDNA and unstable chromosomes, which then are lost or subject to complex rearrangements. This system defines a links between replication-dependent chromosome capping and genome stability in the form of unstable chromosomes.

scholarly journals Sequence and Structure Characteristics of 22 Deletion Breakpoints in Intron 44 of the DMD Gene Based on Long-Read Sequencing

2021 ◽  
Vol 12 ◽  
Author(s):  
Chang Geng ◽  
Yuanren Tong ◽  
Siwen Zhang ◽  
Chao Ling ◽  
Xin Wu ◽  
...  
Keyword(s):  
Becker Muscular Dystrophy ◽  
Repetitive Elements ◽  
Loop Formation ◽  
End Joining ◽  
Origin Firing ◽  
Large Deletions ◽  
Long Read ◽  
Non Homologous End Joining ◽  
Dmd Gene ◽  
Palindromic Sequences

Purpose: Exon deletions make up to 80% of mutations in the DMD gene, which cause Duchenne and Becker muscular dystrophy. Exon 45-55 regions were reported as deletion hotspots and intron 44 harbored more than 25% of deletion start points. We aimed to investigate the fine structures of breakpoints in intron 44 to find potential mechanisms of large deletions in intron 44.Methods: Twenty-two dystrophinopathy patients whose deletion started in intron 44 were sequenced using long-read sequencing of a DMD gene capture panel. Sequence homology, palindromic sequences, and polypyrimidine sequences were searched at the breakpoint junctions. RepeatMasker was used to analyze repetitive elements and Mfold was applied to predict secondary DNA structure.Results: With a designed DMD capture panel, 22 samples achieved 2.25 gigabases and 1.28 million reads on average. Average depth was 308× and 99.98% bases were covered at least 1×. The deletion breakpoints in intron 44 were scattered and no breakpoints clustered in any region less than 500 bp. A total of 72.7% of breakpoints located in distal 100 kb of intron 44 and more repetitive elements were found in this region. Microhomologies of 0–1 bp were found in 36.4% (8/22) of patients, which corresponded with non-homologous end-joining. Microhomologies of 2–20 bp were found in 59.1% (13/22) of patients, which corresponded with microhomology-mediated end-joining. Moreover, a 7 bp insertion was found in one patient, which might be evidence of aberrant replication origin firing. Palindromic sequences, polypyrimidine sequences, and small hairpin loops were found near several breakpoint junctions. No evidence of large hairpin loop formation in deletion root sequences was observed.Conclusion: This study was the first to explore possible mechanisms underlying exon deletions starting from intron 44 of the DMD gene based on long-read sequencing. Diverse mechanisms might be associated with deletions in the DMD gene.

scholarly journals Platelet SHARPIN regulates platelet adhesion and inflammatory responses through associations with αIIbβ3 and LUBAC

2022 ◽  
Author(s):  
Ana Kasirer-Friede ◽  
Emilia Peuhu ◽  
Johanna Ivaska ◽  
Sanford J. Shattil
Keyword(s):  
Inflammatory Responses ◽  
Super Resolution ◽  
Cytoplasmic Tail ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Littermate Control ◽  
Protein Substrates ◽  
Pathway Activation ◽  
Super Resolution Microscopy

Platelets form hemostatic plugs to prevent blood loss and they modulate immunity and inflammation in several ways. A key event during hemostasis is activation of integrin αIIbβ3 through direct interactions of the β3 cytoplasmic tail with talin and kindlin-3. Recently, we showed that human platelets express the adapter molecule, SHARPIN, that can associate directly with the αIIb cytoplasmic tail and can separately promote NF-κB pathway activation as a member of the Met-1 linear ubiquitination activation complex (LUBAC). Here we investigated the role of SHARPIN in platelets after crossing Sharpin flox/flox (fl/fl) mice with PF4-Cre or GPIbα-Cre mice to selectively delete SHARPIN in platelets. SHARPIN-null platelets adhered to immobilized fibrinogen through αIIbβ3, and they spread more extensively than littermate control platelets in a manner dependent on feedback stimulation by platelet adenosine diphosphate (ADP) (P < 0.01). SHARPIN-null platelets showed increased colocalization of αIIbβ3 with talin as assessed by super-resolution microscopy and increased binding of soluble fibrinogen in response to sub-maximal concentrations of ADP (P < 0.05). However, mice with SHARPIN-null platelets showed compromised thrombus growth on collagen and slightly prolonged tail bleeding times. Platelets lacking SHARPIN also showed reduced NF-κB activation and linear ubiquitination of protein substrates upon challenge with classical platelet agonists. Furthermore, the loss of platelet SHARPIN resulted in significant reduction in inflammation in murine models of colitis and peritonitis (P < 0.01). Thus, SHARPIN plays differential and context-dependent roles in platelets to regulate important inflammatory and integrin adhesive functions of these anucleate cells.

Sign in / Sign up

Export Citation Format

Share Document