scholarly journals Quantitative description of early transcriptional response of plant cells to radiation-induced DNA damage using a Poisson initiation event model

2020 ◽  
Vol 26 ◽  
pp. 139-143
Author(s):  
S. V. Litvinov ◽  
N. M. Rashydov
Keyword(s):  
Mathematical Model ◽  
Dna Damage ◽  
Arabidopsis Thaliana ◽  
Dna Repair ◽  
Ionizing Radiation ◽  
Plant Cells ◽  
Transcriptional Response ◽  
Dna Breaks ◽  
Radiation Induced ◽  
Early Transcriptional Response

Aim. One of the problems that have not lost their relevance is the study of the mechanisms of adaptation of higher plants to the effects of radiation associated with the modification of the DNA repair system in response to radiation. This paper presents a Poisson mathematical model of the radiation-induced early transcriptional response of genes of key enzymes, which catalyze recovery of double-stranded DNA breaks in active plant cells. Methods. We used total X-ray irradiation of a model object – 35-day-old Arabidopsis thaliana (L.) Heynh plants at sublethal doses of 3-21 Gy, total RNA extraction, reverse transcription with random hexanucleotide primers, PCR amplification of the obtained cDNA with primers to target genes, fluorescence gel densitometry of amplified products. Results. A mathematical model of transcriptional response to the genotoxic action of ionizing radiation in a subpopulation of active plant cells based on Poisson distribution, which satisfactorily describes the experimental data obtained, is proposed. Conclusions. To initiate a maximal transcriptional response to DNA damage, one two-strand lesion per chromosome, detected by DNA repair systems, is sufficient, while the absence of double-stranded lesions, or the appearance of more than one double-stranded lesion per chromosome inhibits early transcriptional response of the cell on the action of ionizing radiation. The Poisson model of the initiating event makes it possible to predict the response of subpopulations of active cells of angiosperms to the action of genotoxic factors. Keywords: ionizing radiation, DNA damage response (DDR), Arabidopsis thaliana, DNA repair, gene transcriptional activity. 

scholarly journals Cytogenetic and expression markers of individual human radiosensitivity

2018 ◽  
pp. 3-8
Author(s):  
С.А. Васильев ◽  
И.Н. Лебедев
Keyword(s):  
Dna Repair ◽  
Ionizing Radiation ◽  
Radiation Exposure ◽  
Signaling Pathways ◽  
Differentially Expressed Genes ◽  
Transcriptional Response ◽  
Functional Changes ◽  
Individual Radiosensitivity ◽  
Radiation Induced ◽  
Individual Human

Воздействие ионизирующего излучения вызывает значительные функциональные изменения в клетках человека, выражающиеся в активации различных сигнальных путей и транскрипционного ответа множества генов. Величина этих изменений вариабельна у разных индивидов, составляя феномен индивидуальной радиочувствительности. В обзоре рассматриваются известные маркеры индивидуальной радиочувствительности человека, начиная от цитогенетических, позволяющих непосредственно оценить эффективность репарации радиационно-индуцированных повреждений ДНК в клетках, до маркеров, выделенных на основании полногеномных и полнотранскриптомных исследований дифференциально экспрессирующихся генов, обусловливающих различные аспекты клеточного и организменного ответа на радиационное воздействие. Exposure to ionizing radiation causes significant functional changes in human cells which lead to activation of various signaling pathways and transcriptional response of many genes. The magnitude of these changes is variable for different individuals, making the phenomenon of individual radiosensitivity. In the review, markers of individual radiosensitivity are described ranging from cytogenetic markers for assessing the efficiency of DNA repair of radiation-induced damage in cells to genome- and transcriptome-wide approaches to identify differentially expressed genes that determine various aspects of response to radiation exposure.

scholarly journals Chk2 Mediates Stabilization of the FoxM1 Transcription Factor To Stimulate Expression of DNA Repair Genes

2006 ◽  
Vol 27 (3) ◽  
pp. 1007-1016 ◽  
Author(s):  
Yongjun Tan ◽  
Pradip Raychaudhuri ◽  
Robert H. Costa
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Transcription Factor ◽  
Cancer Progression ◽  
Excision Repair ◽  
Transcriptional Response ◽  
Factor X ◽  
Dna Breaks ◽  
Rna Transfection ◽  
Foxm1 Protein

ABSTRACT The forkhead box M1 (FoxM1) transcription factor regulates expression of cell cycle genes essential for DNA replication and mitosis during organ repair and cancer progression. Here, we demonstrate that FoxM1-deficient (−/−) mouse embryonic fibroblasts and osteosarcoma U2OS cells depleted in FoxM1 levels by small interfering RNA transfection display increased DNA breaks, as evidenced by immunofluorescence focus staining for phosphospecific histone H2AX. FoxM1-deficient cells also exhibit stimulation of p53 transcriptional activity, as evidenced by increased expression of the p21cip1 gene. FoxM1-deficient cells display reduced expression of the base excision repair factor X-ray cross-complementing group 1 (XRCC1) and breast cancer-associated gene 2 (BRCA2), the latter of which is involved in homologous recombination repair of DNA double-strand breaks. Furthermore, FoxM1 protein is phosphorylated by checkpoint kinase 2 (Chk2) in response to DNA damage. This phosphorylation of FoxM1 on serine residue 361 caused increased stability of the FoxM1 protein with corresponding increased transcription of XRCC1 and BRCA2 genes, both of which are required for repair of DNA damage. These results identify a novel role for FoxM1 in the transcriptional response during DNA damage/checkpoint signaling and show a novel mechanism by which Chk2 protein regulates expression of DNA repair enzymes.

scholarly journals HPF1 remodels the active site of PARP1 to enable the serine ADP-ribosylation of histones

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fa-Hui Sun ◽  
Peng Zhao ◽  
Nan Zhang ◽  
Lu-Lu Kong ◽  
Catherine C. L. Wong ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Active Site ◽  
Negative Charge ◽  
Structural Data ◽  
Dna Breaks ◽  
Adp Ribosylation ◽  
Local Conformation ◽  
Key Residues ◽  
Structural Insights

AbstractUpon binding to DNA breaks, poly(ADP-ribose) polymerase 1 (PARP1) ADP-ribosylates itself and other factors to initiate DNA repair. Serine is the major residue for ADP-ribosylation upon DNA damage, which strictly depends on HPF1. Here, we report the crystal structures of human HPF1/PARP1-CAT ΔHD complex at 1.98 Å resolution, and mouse and human HPF1 at 1.71 Å and 1.57 Å resolution, respectively. Our structures and mutagenesis data confirm that the structural insights obtained in a recent HPF1/PARP2 study by Suskiewicz et al. apply to PARP1. Moreover, we quantitatively characterize the key residues necessary for HPF1/PARP1 binding. Our data show that through salt-bridging to Glu284/Asp286, Arg239 positions Glu284 to catalyze serine ADP-ribosylation, maintains the local conformation of HPF1 to limit PARP1 automodification, and facilitates HPF1/PARP1 binding by neutralizing the negative charge of Glu284. These findings, along with the high-resolution structural data, may facilitate drug discovery targeting PARP1.

scholarly journals Mechanistic Modelling of DNA Repair and Cellular Survival Following Radiation-Induced DNA Damage

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Stephen J. McMahon ◽  
Jan Schuemann ◽  
Harald Paganetti ◽  
Kevin M. Prise
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Mechanistic Modelling ◽  
Cellular Survival ◽  
Radiation Induced

KGF facilitates repair of radiation-induced DNA damage in alveolar epithelial cells

1997 ◽  
Vol 272 (6) ◽  
pp. L1174-L1180 ◽  
Author(s):  
M. Takeoka ◽  
W. F. Ward ◽  
H. Pollack ◽  
D. W. Kamp ◽  
R. J. Panos
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Epithelial Cells ◽  
Dna Polymerase ◽  
Dna Polymerases ◽  
Dna Strand Breaks ◽  
Strand Breaks ◽  
Alveolar Epithelial ◽  
Radiation Induced ◽  
Dna Strand

Administration of exogenous keratinocyte growth factor (KGF) prevents or attenuates several forms of oxidant-mediated lung injury. Because DNA damage in epithelial cells is a component of radiation pneumotoxicity, we determined whether KGF ameliorated DNA strand breaks in irradiated A549 cells. Cells were exposed to 137Cs gamma rays, and DNA damage was measured by alkaline unwinding and ethidium bromide fluorescence after a 30-min recovery period. Radiation induced a dose-dependent increase in DNA strand breaks. The percentage of double-stranded DNA after exposure to 30 Gy increased from 44.6 +/- 3.5% in untreated control cells to 61.6 +/- 5.0% in cells cultured with 100 ng/ml KGF for 24 h (P < 0.05). No reduction in DNA damage occurred when the cells were cultured with KGF but maintained at 0 degree C during and after irradiation. The sparing effect of KGF on radiation-induced DNA damage was blocked by aphidicolin, an inhibitor of DNA polymerases-alpha, -delta, and -epsilon and by butylphenyl dGTP, which blocks DNA polymerase-alpha strongly and polymerases-delta and -epsilon less effectively. However, dideoxythymidine triphosphate, a specific inhibitor of DNA polymerase-beta, did not abrogate the KGF effect. Thus KGF increases DNA repair capacity in irradiated pulmonary epithelial cells, an effect mediated at least in part by DNA polymerases-alpha, -delta, and -epsilon. Enhancement of DNA repair capability after cell damage may be one mechanism by which KGF is able to ameliorate oxidant-mediated alveolar epithelial injury.

scholarly journals Truncated PPM1D Prevents Apoptosis in the Murine Thymus and Promotes Ionizing Radiation-Induced Lymphoma

Cells ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 2068
Author(s):  
Andra S. Martinikova ◽  
Monika Burocziova ◽  
Miroslav Stoyanov ◽  
Libor Macurek
Keyword(s):  
Dna Damage ◽  
Ionizing Radiation ◽  
Tumor Formation ◽  
Cell Cycle Checkpoints ◽  
Negative Regulator ◽  
Tumor Suppressor P53 ◽  
Mouse Thymus ◽  
Truncating Mutation ◽  
T Cell Lymphomas ◽  
Radiation Induced

Genome integrity is protected by the cell-cycle checkpoints that prevent cell proliferation in the presence of DNA damage and allow time for DNA repair. The transient checkpoint arrest together with cellular senescence represent an intrinsic barrier to tumorigenesis. Tumor suppressor p53 is an integral part of the checkpoints and its inactivating mutations promote cancer growth. Protein phosphatase magnesium-dependent 1 (PPM1D) is a negative regulator of p53. Although its loss impairs recovery from the G2 checkpoint and promotes induction of senescence, amplification of the PPM1D locus or gain-of-function truncating mutations of PPM1D occur in various cancers. Here we used a transgenic mouse model carrying a truncating mutation in exon 6 of PPM1D (Ppm1dT). As with human cell lines, we found that the truncated PPM1D was present at high levels in the mouse thymus. Truncated PPM1D did not affect differentiation of T-cells in the thymus but it impaired their response to ionizing radiation (IR). Thymocytes in Ppm1dT/+ mice did not arrest in the checkpoint and continued to proliferate despite the presence of DNA damage. In addition, we observed a decreased level of apoptosis in the thymi of Ppm1dT/+ mice. Moreover, the frequency of the IR-induced T-cell lymphomas increased in Ppm1dT/+Trp53+/− mice resulting in decreased survival. We conclude that truncated PPM1D partially suppresses the p53 pathway in the mouse thymus and potentiates tumor formation under the condition of a partial loss of p53 function.

scholarly journals Veliparib Is an Effective Radiosensitizing Agent in a Preclinical Model of Medulloblastoma

2021 ◽  
Vol 8 ◽  
Author(s):  
Jessica Buck ◽  
Patrick J. C. Dyer ◽  
Hilary Hii ◽  
Brooke Carline ◽  
Mani Kuchibhotla ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Combination Therapy ◽  
Cellular Response ◽  
Molecular Subtype ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Parp Inhibition ◽  
Preclinical Model ◽  
Radiation Induced

Medulloblastoma is the most common malignant childhood brain tumor, and 5-year overall survival rates are as low as 40% depending on molecular subtype, with new therapies critically important. As radiotherapy and chemotherapy act through the induction of DNA damage, the sensitization of cancer cells through the inhibition of DNA damage repair pathways is a potential therapeutic strategy. The poly-(ADP-ribose) polymerase (PARP) inhibitor veliparib was assessed for its ability to augment the cellular response to radiation-induced DNA damage in human medulloblastoma cells. DNA repair following irradiation was assessed using the alkaline comet assay, with veliparib inhibiting the rate of DNA repair. Veliparib treatment also increased the number of γH2AX foci in cells treated with radiation, and analysis of downstream pathways indicated persistent activation of the DNA damage response pathway. Clonogenicity assays demonstrated that veliparib effectively inhibited the colony-forming capacity of medulloblastoma cells, both as a single agent and in combination with irradiation. These data were then validated in vivo using an orthotopic implant model of medulloblastoma. Mice harboring intracranial D425 medulloblastoma xenografts were treated with vehicle, veliparib, 18 Gy multifractionated craniospinal irradiation (CSI), or veliparib combined with 18 Gy CSI. Animals treated with combination therapy exhibited reduced tumor growth rates concomitant with increased intra-tumoral apoptosis observed by immunohistochemistry. Kaplan–Meier analyses revealed a statistically significant increase in survival with combination therapy compared to CSI alone. In summary, PARP inhibition enhanced radiation-induced cytotoxicity of medulloblastoma cells; thus, veliparib or other brain-penetrant PARP inhibitors are potential radiosensitizing agents for the treatment of medulloblastoma.

scholarly journals DNA damage shifts circadian clock time via Hausp-dependent Cry1 stabilization

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Stephanie J Papp ◽  
Anne-Laure Huber ◽  
Sabine D Jordan ◽  
Anna Kriebs ◽  
Madelena Nguyen ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Circadian Clock ◽  
Transcriptional Response ◽  
Genotoxic Stress ◽  
Genomic Integrity ◽  
Clock Time ◽  
Dna Repair Enzymes ◽  
Repair Enzymes ◽  
Specific Protease

The circadian transcriptional repressors cryptochrome 1 (Cry1) and 2 (Cry2) evolved from photolyases, bacterial light-activated DNA repair enzymes. In this study, we report that while they have lost DNA repair activity, Cry1/2 adapted to protect genomic integrity by responding to DNA damage through posttranslational modification and coordinating the downstream transcriptional response. We demonstrate that genotoxic stress stimulates Cry1 phosphorylation and its deubiquitination by Herpes virus associated ubiquitin-specific protease (Hausp, a.k.a Usp7), stabilizing Cry1 and shifting circadian clock time. DNA damage also increases Cry2 interaction with Fbxl3, destabilizing Cry2. Thus, genotoxic stress increases the Cry1/Cry2 ratio, suggesting distinct functions for Cry1 and Cry2 following DNA damage. Indeed, the transcriptional response to genotoxic stress is enhanced in Cry1−/− and blunted in Cry2−/− cells. Furthermore, Cry2−/− cells accumulate damaged DNA. These results suggest that Cry1 and Cry2, which evolved from DNA repair enzymes, protect genomic integrity via coordinated transcriptional regulation.

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