So similar yet so different: The two ends of a double strand break

Kim, Keun Pil; Mirkin, Ekaterina V.

doi:10.1016/j.mrfmmm.2017.06.007

Cited by 24 publications

(21 citation statements)

References 112 publications

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“…Thus, a negative correlation between the number of constitutive (metabolic) γH2AX foci and the fraction of senescent cells among proliferating cells might have a tempting logical explanation - the higher the proliferative activity, the lower the proportion of senescent cells among the fibroblast population and vice versa. The only exact mechanism of homologous recombination [36,37] repairs the resulting DSBs by ATR kinase mediating histone H2AX phosphorylation [38,39]. DSBs formed during DNA damage by various genotoxic factors, including free radicals formed during cellular respiration, have a completely different meaning for the fate of the cell and its descendants.…”

Section: Discussionmentioning

confidence: 99%

Spontaneous γH2AX foci in human dermal fibroblasts in relation to proliferation activity and aging

Zorin

Grekhova

Pustovalova

et al. 2019

Aging

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We assessed the effects of donor age on clonogenicity, proliferative potential, and spontaneous γH2AX foci in the proliferating (Ki67 +) and senescent (SA β-gal +) cultures of skin fibroblasts isolated from 34 donors of different age (23-82 years). Here, we demonstrated that neither the colony forming effectiveness of proliferating (Ki67+) fraction of the fibroblasts nor the average number of γH2AX foci of the same fraction does not depend on the age of the donor. The correlation between the number of γH2AX foci and the donor’s age was reliable in quiescent (Ki67-) cells. The average number of γH2AX foci in quiescent fibroblasts of donors older than 68 years was about two times higher than in the same cells of up to 30 years old donors. The number of γH2AX foci demonstrated a statistically significant positive correlation with the fraction of proliferating cells in fibroblast cultures. On average, proliferating cells have twice as many the γH2AX foci in comparison with the quiescent cells. Within a population of proliferating (Ki67+) cells, the degree of senescence correlated with a relative declining of constitutive γH2AX foci number, whereas in the population of quiescent (Ki67-) cells, it was proportional to augmenting the number of the γH2AX foci. Our data on a statistically significant (p=0.001) correlation between the age of the donor and the number of constitutive γH2AX foci in quiescent cells, could point out the ongoing DNA-damage response due in the maintenance of the senescent state of cells.

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Section: Discussionmentioning

confidence: 99%

Spontaneous γH2AX foci in human dermal fibroblasts in relation to proliferation activity and aging

Zorin

Grekhova

Pustovalova

et al. 2019

Aging

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“…These errors may be a result of an increased generation of reactive oxygen and nitrogen species characteristic of the S-phase metabo-lism and low-dose radiation can stimulate proliferation [ 49 – 51 ]. Unlike DNA double-strand breaks directly induced by radiation (or by water hydrolysis products upon irradiation), S-phase replication errors typically result in single-stranded DNA lesions and single-ended DNA double-strand breaks that trigger activation of and are processed by the ATR kinase via homologous recombination only [ 42 , 52 ]. This is a substantially slower DNA repair pathway compared to non-homologous end-joining of double-strand breaks; however, typically about 80 % of the radiation-induced DSBs are processed by the fast NHEJ mechanism [ 39 , 41 ].…”

Section: Discussionmentioning

confidence: 99%

Residual γH2AX foci induced by low dose x-ray radiation in bone marrow mesenchymal stem cells do not cause accelerated senescence in the progeny of irradiated cells

Pustovalova

Астрелина

Grekhova

et al. 2017

Aging

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Mechanisms underlying the effects of low-dose ionizing radiation (IR) exposure (10-100 mGy) remain unknown. Here we present a comparative study of early (less than 24h) and delayed (up to 11 post-irradiation passages) radiation effects caused by low (80 mGy) vs intermediate (1000 mGy) dose X-ray exposure in cultured human bone marrow mesenchymal stem cells (MSCs). We show that γН2АХ foci induced by an intermediate dose returned back to the control value by 24 h post-irradiation. In contrast, low-dose irradiation resulted in residual γН2АХ foci still present at 24 h. Notably, these low dose induced residual γН2АХ foci were not co-localized with рАТМ foci and were observed predominantly in the proliferating Кi67 positive (Кi67+) cells. The number of γН2АХ foci and the fraction of nonproliferating (Кi67-) and senescent (SA-β-gal+) cells measured at passage 11 were increased in cultures exposed to an intermediate dose compared to unirradiated controls. These delayed effects were not seen in the progeny of cells that were irradiated with low-dose X-rays, although such exposure resulted in residual γН2АХ foci in directly irradiated cells. Taken together, our results support the hypothesis that the low-dose IR induced residual γH2AХ foci do not play a role in delayed irradiation consequences, associated with cellular senescence in cultured MSCs.

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“…The MRE11-RAD50-NBS1 (MRN, MRX in yeast) complex recognizes dsDNA and first creates a nick 15–20 bp from the 5′-ends of the DSB (Symington, 2014). Exonucleases such as SGS1-DNA2 and EXO1 complete the resection step (Kim and Mirkin, 2018). It then moves into flanking dsDNA regions and recruits ataxia telangiectasia mutated (ATM) kinase, the key upstream kinase of DSB signaling (Falck et al, 2005), and interacts with CtIP (Makharashvili and Paull, 2015).…”

Section: Hdr Pathwaymentioning

confidence: 99%

“…The assembly of a RAD51 nucleoprotein filament promotes homologous search by locating and pairing the 3′-overhang with a homologous duplex DNA and catalyzing strand invasion (termed single-end invasion, SEI) (Morrical, 2015; Ma et al, 2017). The two ends of the DSB are identical, but one end serves as the “first end,” which searches for the homologous sequence and forms a displacement loops (D-loops) structure while the other end waits for the latter process (Kim and Mirkin, 2018). Besides RAD51, DNA strand exchange also requires RAD54 and RDH54/TID1, which performs this step by stabilizing RAD51-ssDNA presynaptic filaments (Mazin et al, 2003).…”

Section: Hdr Pathwaymentioning

confidence: 99%

Methodologies for Improving HDR Efficiency

et al. 2019

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Clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) is a precise genome manipulating technology that can be programmed to induce double-strand break (DSB) in the genome wherever needed. After nuclease cleavage, DSBs can be repaired by non-homologous end joining (NHEJ) or homology-directed repair (HDR) pathway. For producing targeted gene knock-in or other specific mutations, DSBs should be repaired by the HDR pathway. While NHEJ can cause various length insertions/deletion mutations (indels), which can lead the targeted gene to lose its function by shifting the open reading frame (ORF). Furthermore, HDR has low efficiency compared with the NHEJ pathway. In order to modify the gene precisely, numerous methods arose by inhibiting NHEJ or enhancing HDR, such as chemical modulation, synchronized expression, and overlapping homology arm. Here we focus on the efficiency and other considerations of these methodologies.

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So similar yet so different: The two ends of a double strand break

Cited by 24 publications

References 112 publications

Spontaneous γH2AX foci in human dermal fibroblasts in relation to proliferation activity and aging

Spontaneous γH2AX foci in human dermal fibroblasts in relation to proliferation activity and aging

Residual γH2AX foci induced by low dose x-ray radiation in bone marrow mesenchymal stem cells do not cause accelerated senescence in the progeny of irradiated cells

Methodologies for Improving HDR Efficiency

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