DNA double strand breaks induced by the indirect effect of radiation are more efficiently repaired by non-homologous end joining compared to homologous recombination repair

2013 ◽  
Vol 756 (1-2) ◽  
pp. 21-29 ◽  
Author(s):  
Ainars Bajinskis ◽  
Adayapalam T. Natarajan ◽  
Klaus Erixon ◽  
Mats Harms-Ringdahl
Keyword(s):  
Homologous Recombination ◽  
Indirect Effect ◽  
Double Strand Breaks ◽  
Homologous Recombination Repair ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Recombination Repair ◽  
Non Homologous End Joining

scholarly journals miR-21-mediated Radioresistance Occurs via Promoting Repair of DNA Double Strand Breaks

2017 ◽  
Vol 292 (8) ◽  
pp. 3531-3540 ◽  
Author(s):  
Baocheng Hu ◽  
Xiang Wang ◽  
Shuofeng Hu ◽  
Xiaomin Ying ◽  
Ping Wang ◽  
...  
Keyword(s):  
Cyclin D1 ◽  
Opposite Effect ◽  
Double Strand Breaks ◽  
Human Tumors ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Recombination Repair ◽  
Non Homologous End Joining ◽  
Novel Target

miR-21, as an oncogene that overexpresses in most human tumors, is involved in radioresistance; however, the mechanism remains unclear. Here, we demonstrate that miR-21-mediated radioresistance occurs through promoting repair of DNA double strand breaks, which includes facilitating both non-homologous end-joining (NHEJ) and homologous recombination repair (HRR). The miR-21-promoted NHEJ occurs through targeting GSK3B (a novel target of miR-21), which affects the CRY2/PP5 pathway and in turn increases DNA-PKcs activity. The miR-21-promoted HRR occurs through targeting both GSK3B and CDC25A (a known target of miR-21), which neutralizes the effects of targeting GSK3B-induced CDC25A increase because GSK3B promotes degradation of both CDC25A and cyclin D1, but CDC25A and cyclin D1 have an opposite effect on HRR. A negative correlation of expression levels between miR-21 and GSK3β exists in a subset of human tumors. Our results not only elucidate miR-21-mediated radioresistance, but also provide potential new targets for improving radiotherapy.

scholarly journals ATR inhibition enhances 5-fluorouracil sensitivity independent of non-homologous end-joining and homologous recombination repair pathway

2020 ◽  
Author(s):  
Soichiro S. Ito ◽  
Yosuke Nakagawa ◽  
Masaya Matsubayashi ◽  
Yoshihiko M. Sakaguchi ◽  
Shinko Kobashigawa ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Homologous Recombination Repair ◽  
Dna Double Strand Breaks ◽  
Dna Breaks ◽  
End Joining ◽  
Drug Induced ◽  
Nucleotide Synthesis ◽  
Double Strand Dna Breaks ◽  
Recombination Repair ◽  
Non Homologous End Joining

ABSTRACTThe anticancer agent, 5-fluorouracil (5-FU), is typically applied in the treatment of various types of cancers because of its properties. Thought to be an inhibitor of the enzyme thymidylate synthase which plays a role in nucleotide synthesis, 5-FU has been found to induce single- and double-strand DNA breaks. The activation of ATR occurs as a reaction to UV- and chemotherapeutic drug-induced replication stress. In this study, we examined the effect of ATR inhibition on 5-FU sensitivity. Using western blotting, we found that 5-FU treatment led to the phosphorylation of ATR. Surviving fractions were remarkably decreased in 5-FU with ATR inhibitor (ATRi) compared to 5-FU with other major DNA repair kinases inhibitors. ATR inhibition enhanced induction of DNA double-strand breaks and apoptosis in 5-FU-treated cells. Using gene expression analysis, we found that 5-FU could induce the activation of intra-S checkpoint. Surprisingly, BRCA2-deficient cells were sensitive to 5-FU in the presence of ATRi. In addition, ATR inhibition enhanced the efficacy of 5-FU treatment, independent of non-homologous end-joining and homologous recombination repair pathways. Findings from the present study suggest ATR as a potential therapeutic target for 5-FU chemotherapy.

scholarly journals Depletion of Akt1 and Akt2 Impairs the Repair of Radiation-Induced DNA Double Strand Breaks via Homologous Recombination

2019 ◽  
Vol 20 (24) ◽  
pp. 6316 ◽  
Author(s):  
Tahereh Mohammadian Gol ◽  
H. Peter Rodemann ◽  
Klaus Dittmann
Keyword(s):  
Homologous Recombination ◽  
Double Strand Breaks ◽  
Major Protein ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Knock Out ◽  
Strand Breaks ◽  
Protein Levels ◽  
Non Homologous End Joining

Homologous recombination repair (HRR), non-homologous end-joining (NHEJ) and alternative NHEJ are major pathways that are utilized by cells for processing DNA double strand breaks (DNA-DSBs); their function plays an important role in the radiation resistance of tumor cells. Conflicting data exist regarding the role of Akt in homologous recombination (HR), i.e., the regulation of Rad51 as a major protein of this pathway. This study was designed to investigate the specific involvement of Akt isoforms in HRR. HCT116 colon cancer cells with stable AKT-knock-out and siRNA-mediated AKT-knockdown phenotypes were used to investigate the role of Akt1 and Akt2 isoforms in HR. The results clearly demonstrated that HCT116 AKT1-KO and AKT2-KO cells have a significantly reduced Rad51 foci formation 6 h post irradiation versus parental cells. Depletion of Akt1 and Akt2 protein levels as well as inhibition of Akt kinase activity resulted in an increased number of residual-γH2AX in CENP-F positive cells mainly representing the S and G2 phase cells. Furthermore, inhibition of NHEJ and HR using DNA-PK and Rad51 antagonists resulted in stronger radiosensitivity of AKT1 and AKT2 knockout cells versus wild type cells. These data collectively show that both Akt1 and Akt2 are involved in DSBs repair through HRR.

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