scholarly journals Development of a quantitative pharmacodynamic assay for apoptosis in fixed tumor tissue and its application in distinguishing cytotoxic drug—induced DNA double strand breaks from DNA double strand breaks associated with apoptosis

Oncotarget ◽  
2018 ◽  
Vol 9 (24) ◽  
pp. 17104-17116 ◽  
Author(s):  
Angie B. Dull ◽  
Deborah Wilsker ◽  
Melinda Hollingshead ◽  
Christina Mazcko ◽  
Christina M. Annunziata ◽  
...  
Keyword(s):  
Tumor Tissue ◽  
Double Strand Breaks ◽  
Cytotoxic Drug ◽  
Dna Double Strand Breaks ◽  
Drug Induced ◽  
Strand Breaks ◽  
Fixed Tumor

scholarly journals Mdt1 Facilitates Efficient Repair of Blocked DNA Double-Strand Breaks and Recombinational Maintenance of Telomeres

2007 ◽  
Vol 27 (18) ◽  
pp. 6532-6545 ◽  
Author(s):  
Brietta L. Pike ◽  
Jörg Heierhorst
Keyword(s):  
Dna Recombination ◽  
Double Strand Breaks ◽  
Telomere Maintenance ◽  
Type I ◽  
Dna Double Strand Breaks ◽  
Drug Induced ◽  
Exogenous Dna ◽  
Strand Breaks ◽  
Dramatic Shift ◽  
Recombination Pathway

ABSTRACT DNA recombination plays critical roles in DNA repair and alternative telomere maintenance. Here we show that absence of the SQ/TQ cluster domain-containing protein Mdt1 (Ybl051c) renders Saccharomyces cerevisiae particularly hypersensitive to bleomycin, a drug that causes 3′-phospho-glycolate-blocked DNA double-strand breaks (DSBs). mdt1Δ also hypersensitizes partially recombination-defective cells to camptothecin-induced 3′-phospho-tyrosyl protein-blocked DSBs. Remarkably, whereas mdt1Δ cells are unable to restore broken chromosomes after bleomycin treatment, they efficiently repair “clean” endonuclease-generated DSBs. Epistasis analyses indicate that MDT1 acts in the repair of bleomycin-induced DSBs by regulating the efficiency of the homologous recombination pathway as well as telomere-related functions of the KU complex. Moreover, mdt1Δ leads to severe synthetic growth defects with a deletion of the recombination facilitator and telomere-positioning factor gene CTF18 already in the absence of exogenous DNA damage. Importantly, mdt1Δ causes a dramatic shift from the usually prevalent type II to the less-efficient type I pathway of recombinational telomere maintenance in the absence of telomerase in liquid senescence assays. As telomeres resemble protein-blocked DSBs, the results indicate that Mdt1 acts in a novel blocked-end-specific recombination pathway that is required for the efficiency of both drug-induced DSB repair and telomerase-independent telomere maintenance.

Reduction in drug-induced DNA double-strand breaks associated with β1 integrin–mediated adhesion correlates with drug resistance in U937 cells

Blood ◽  
2001 ◽  
Vol 98 (6) ◽  
pp. 1897-1903 ◽  
Author(s):  
Lori A. Hazlehurst ◽  
Nikola Valkov ◽  
Lee Wisner ◽  
Jonathan A. Storey ◽  
David Boulware ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cellular Adhesion ◽  
Double Strand Breaks ◽  
U937 Cells ◽  
Dna Double Strand Breaks ◽  
Drug Induced ◽  
Strand Breaks ◽  
Β1 Integrins ◽  
Topo Ii ◽  
Initial Drug

Abstract We previously showed that adhesion of myeloma cells to fibronectin (FN) by means of β1 integrins causes resistance to certain cytotoxic drugs. The study described here found that adhesion of U937 human histiocytic lymphoma cells to FN provides a survival advantage with respect to damage induced by the topoisomerase (topo) II inhibitors mitoxantrone, doxorubicin, and etoposide. Apoptosis induced by a topo II inhibitor is thought to be initiated by DNA damage. The neutral comet assay was used to determine whether initial drug-induced DNA damage correlated with cellular-adhesion–mediated drug resistance. Cellular adhesion by means of β1 integrins resulted in a 40% to 60% reduction in mitoxantrone- and etoposide-induced DNA double-strand breaks. When the mechanisms regulating the initial drug-induced DNA damage were examined, a β1 integrin–mediated reduction in drug-induced DNA double-strand breaks was found to correlate with reduced topo II activity and decreased salt-extractable nuclear topo IIβ protein levels. Confocal studies showed changes in the nuclear localization of topo IIβ; however, alterations in the nuclear-to-cytoplasmic ratio of topo IIβ in FN-adhered cells were not significantly different. Furthermore, after a high level of salt extraction of nuclear proteins, higher levels of topo IIβ–associated DNA binding were observed in FN-adhered cells than in cells in suspension. Together, these data suggest that topo IIβ is more tightly bound to the nucleus of FN-adhered cells. Thus, FN adhesion by means of β1 integrins appears to protect U937 cells from initial drug-induced DNA damage by reducing topo II activity secondarily to alterations in the nuclear distribution of topo IIβ.

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.

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