scholarly journals Regulation and Localization of the Bloom Syndrome Protein in Response to DNA Damage

2001 ◽  
Vol 153 (2) ◽  
pp. 367-380 ◽  
Author(s):  
Oliver Bischof ◽  
Sahn-Ho Kim ◽  
John Irving ◽  
Sergey Beresten ◽  
Nathan A. Ellis ◽  
...  
Keyword(s):  
Dna Damage ◽  
Nuclear Matrix ◽  
Autosomal Recessive Disorder ◽  
Bloom Syndrome ◽  
Nuclear Bodies ◽  
Strand Breaks ◽  
Pml Nuclear Bodies ◽  
Radiation Induced ◽  
Syndrome Protein ◽  
G2 Delay

Bloom syndrome (BS) is an autosomal recessive disorder characterized by a high incidence of cancer and genomic instability. BLM, the protein defective in BS, is a RecQ-like helicase, presumed to function in DNA replication, recombination, or repair. BLM localizes to promyelocytic leukemia protein (PML) nuclear bodies and is expressed during late S and G2. We show, in normal human cells, that the recombination/repair proteins hRAD51 and replication protein (RP)-A assembled with BLM into a fraction of PML bodies during late S/G2. Biochemical experiments suggested that BLM resides in a nuclear matrix–bound complex in which association with hRAD51 may be direct. DNA-damaging agents that cause double strand breaks and a G2 delay induced BLM by a p53- and ataxia-telangiectasia mutated independent mechanism. This induction depended on the G2 delay, because it failed to occur when G2 was prevented or bypassed. It coincided with the appearance of foci containing BLM, PML, hRAD51 and RP-A, which resembled ionizing radiation-induced foci. After radiation, foci containing BLM and PML formed at sites of single-stranded DNA and presumptive repair in normal cells, but not in cells with defective PML. Our findings suggest that BLM is part of a dynamic nuclear matrix–based complex that requires PML and functions during G2 in undamaged cells and recombinational repair after DNA damage.

scholarly journals Human papillomavirus E7 oncoprotein targets RNF168 to hijack the host DNA damage response

2019 ◽  
Vol 116 (39) ◽  
pp. 19552-19562 ◽  
Author(s):  
Justine Sitz ◽  
Sophie Anne Blanchet ◽  
Steven F. Gameiro ◽  
Elise Biquand ◽  
Tia M. Morgan ◽  
...  
Keyword(s):  
Cervical Cancer ◽  
Dna Damage ◽  
Cancer Cells ◽  
Genomic Instability ◽  
E3 Ligase ◽  
Human Papillomaviruses ◽  
Double Strand Breaks ◽  
Nuclear Bodies ◽  
Dna Double Strand Breaks ◽  
Strand Breaks

High-risk human papillomaviruses (HR-HPVs) promote cervical cancer as well as a subset of anogenital and head and neck cancers. Due to their limited coding capacity, HPVs hijack the host cell’s DNA replication and repair machineries to replicate their own genomes. How this host–pathogen interaction contributes to genomic instability is unknown. Here, we report that HPV-infected cancer cells express high levels of RNF168, an E3 ubiquitin ligase that is critical for proper DNA repair following DNA double-strand breaks, and accumulate high numbers of 53BP1 nuclear bodies, a marker of genomic instability induced by replication stress. We describe a mechanism by which HPV E7 subverts the function of RNF168 at DNA double-strand breaks, providing a rationale for increased homology-directed recombination in E6/E7-expressing cervical cancer cells. By targeting a new regulatory domain of RNF168, E7 binds directly to the E3 ligase without affecting its enzymatic activity. As RNF168 knockdown impairs viral genome amplification in differentiated keratinocytes, we propose that E7 hijacks the E3 ligase to promote the viral replicative cycle. This study reveals a mechanism by which tumor viruses reshape the cellular response to DNA damage by manipulating RNF168-dependent ubiquitin signaling. Importantly, our findings reveal a pathway by which HPV may promote the genomic instability that drives oncogenesis.

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 Bloom syndrome protein restrains innate immune sensing of micronuclei by cGAS

2019 ◽  
Vol 216 (5) ◽  
pp. 1199-1213 ◽  
Author(s):  
Matthieu Gratia ◽  
Mathieu P. Rodero ◽  
Cécile Conrad ◽  
Elias Bou Samra ◽  
Mathieu Maurin ◽  
...  
Keyword(s):  
Dna Damage ◽  
Immune Responses ◽  
Genome Instability ◽  
Bloom Syndrome ◽  
Innate Immune ◽  
Genome Integrity ◽  
Immune Sensing ◽  
Syndrome Protein ◽  
Innate Immune Sensing ◽  
Exonuclease Trex1

Cellular innate immune sensors of DNA are essential for host defense against invading pathogens. However, the presence of self-DNA inside cells poses a risk of triggering unchecked immune responses. The mechanisms limiting induction of inflammation by self-DNA are poorly understood. BLM RecQ–like helicase is essential for genome integrity and is deficient in Bloom syndrome (BS), a rare genetic disease characterized by genome instability, accumulation of micronuclei, susceptibility to cancer, and immunodeficiency. Here, we show that BLM-deficient fibroblasts show constitutive up-regulation of inflammatory interferon-stimulated gene (ISG) expression, which is mediated by the cGAS–STING–IRF3 cytosolic DNA–sensing pathway. Increased DNA damage or down-regulation of the cytoplasmic exonuclease TREX1 enhances ISG expression in BLM-deficient fibroblasts. cGAS-containing cytoplasmic micronuclei are increased in BS cells. Finally, BS patients demonstrate elevated ISG expression in peripheral blood. These results reveal that BLM limits ISG induction, thus connecting DNA damage to cellular innate immune response, which may contribute to human pathogenesis.

scholarly journals Protective Activity of C-Geranylflavonoid Analogs from Paulownia tomentosa against DNA Damage in 137Cs Irradiated AHH-1Cells

2014 ◽  
Vol 9 (9) ◽  
pp. 1934578X1400900
Author(s):  
Hyung-In Moon ◽  
Min Ho Jeong ◽  
Wol Soon Jo
Keyword(s):  
Dna Damage ◽  
Protective Effects ◽  
Strand Breaks ◽  
Human Lymphoblastoid Cell ◽  
Wide Range ◽  
Radiation Induced ◽  
Anti Oxidant ◽  
Dna Strand ◽  
Cellular Dna

Radiotherapy is an important form of treatment for a wide range of cancers, but it can damage DNA and cause adverse effects. We investigated if the diplacone analogs of P. tomentosa were radio-protective in a human lymphoblastoid cell line (AHH-1). Four geranylated flavonoids, diplacone, 3′- O-methyl-5′-hydroxydiplacone, 3′- O-methyl-5′- O-methyldiplacone and 3′- O-methyldiplacol, were tested for their antioxidant and radio-protective effects. Diplacone analogs effectively scavenged free radicals and inhibited radiation-induced DNA strand breaks in vitro. They significantly decreased levels of reactive oxygen species and cellular DNA damage in 2 Gy-irradiated AHH-1 cells. Glutathione levels and superoxide dismutase activity in irradiated AHH-1 cells increased significantly after treatment with these analogs. The enhanced biological anti-oxidant activity and radioprotective activity of diplacone analogs maintained the survival of irradiated AHH-1 cells in a clonogenic assay. These data suggest that diplacone analogs may protect healthy tissue surrounding tumor cells during radiotherapy to ensure better control of radiotherapy and allow higher doses of radiotherapy to be employed.

PML nuclear bodies are recruited to persistent DNA damage lesions in an RNF168-53BP1 dependent manner and contribute to DNA repair

DNA Repair ◽  
2019 ◽  
Vol 78 ◽  
pp. 114-127 ◽  
Author(s):  
Marketa Vancurova ◽  
Hana Hanzlikova ◽  
Lucie Knoblochova ◽  
Jan Kosla ◽  
Dusana Majera ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Nuclear Bodies ◽  
Dependent Manner ◽  
Pml Nuclear Bodies

scholarly journals Role of inhibitory CDC2 phosphorylation in radiation-induced G2 arrest in human cells.

1996 ◽  
Vol 134 (4) ◽  
pp. 963-970 ◽  
Author(s):  
P Jin ◽  
Y Gu ◽  
D O Morgan
Keyword(s):  
Dna Damage ◽  
Chromatin Condensation ◽  
S Phase ◽  
Human Cells ◽  
G2 Arrest ◽  
Hela Cell Lines ◽  
Radiation Induced ◽  
G2 Delay ◽  
In Cells

The activity of the mitosis-promoting kinase CDC2-cyclin B is normally suppressed in S phase and G2 by inhibitory phosphorylation at Thr14 and Tyr15. This work explores the possibility that these phosphorylations are responsible for the G2 arrest that occurs in human cells after DNA damage. HeLa cell lines were established in which CDC2AF, a mutant that cannot be phosphorylated at Thr14 and Tyr15, was expressed from a tetracycline-repressible promoter. Expression of CDC2AF did not induce mitotic events in cells arrested at the beginning of S phase with DNA synthesis inhibitors, but induced low levels of premature chromatin condensation in cells progressing through S phase and G2. Expression of CDC2AF greatly reduced the G2 delay that resulted when cells were X-irradiated in S phase. However, a significant G2 delay was still observed and was accompanied by high CDC2-associated kinase activity. Expression of wild-type CDC2, or the related kinase CDK2AF, had no effect on the radiation-induced delay. Thus, inhibitory phosphorylation of CDC2, as well as additional undefined mechanisms, delay mitosis after DNA damage.

scholarly journals Influence of Acute Exercise on DNA Repair and PARP Activity before and after Irradiation in Lymphocytes from Trained and Untrained Individuals

2019 ◽  
Vol 20 (12) ◽  
pp. 2999 ◽  
Author(s):  
Maria Moreno-Villanueva ◽  
Andreas Kramer ◽  
Tabea Hammes ◽  
Maria Venegas-Carro ◽  
Patrick Thumm ◽  
...  
Keyword(s):  
Physical Activity ◽  
Dna Damage ◽  
Dna Repair ◽  
Immune Cells ◽  
Acute Exercise ◽  
Dna Strand Breaks ◽  
Strand Breaks ◽  
Before And After ◽  
Radiation Induced ◽  
Dna Strand

Several studies indicate that acute exercise induces DNA damage, whereas regular exercise increases DNA repair kinetics. Although the molecular mechanisms are not completely understood, the induction of endogenous reactive oxygen species (ROS) during acute exhaustive exercise due to metabolic processes might be responsible for the observed DNA damage, while an adaptive increase in antioxidant capacity due to regular physical activity seems to play an important protective role. However, the protective effect of physical activity on exogenously induced DNA damage in human immune cells has been poorly investigated. We asked the question whether individuals with a high aerobic capacity would have an enhanced response to radiation-induced DNA damage. Immune cells are highly sensitive to radiation and exercise affects lymphocyte dynamics and immune function. Therefore, we measured endogenous and radiation-induced DNA strand breaks and poly (ADP-ribose) polymerase-1 (PARP1) activity in peripheral blood mononuclear cells (PBMCs) from endurance-trained (maximum rate of oxygen consumption measured during incremental exercise V’O2max > 55 mL/min/kg) and untrained (V’O2max < 45 mL/min/kg) young healthy male volunteers before and after exhaustive exercise. Our results indicate that: (i) acute exercise induces DNA strand breaks in lymphocytes only in untrained individuals, (ii) following acute exercise, trained individuals repaired radiation-induced DNA strand breaks faster than untrained individuals, and (iii) trained subjects retained a higher level of radiation-induced PARP1 activity after acute exercise. The results of the present study indicate that increased aerobic fitness can protect immune cells against radiation-induced DNA strand breaks.

scholarly journals Phosphorylation of BLM, Dissociation from Topoisomerase IIIα, and Colocalization with γ-H2AX after Topoisomerase I-Induced Replication Damage

2005 ◽  
Vol 25 (20) ◽  
pp. 8925-8937 ◽  
Author(s):  
V. Ashutosh Rao ◽  
Angela M. Fan ◽  
LingHua Meng ◽  
Christopher F. Doe ◽  
Phillip S. North ◽  
...  
Keyword(s):  
Topoisomerase I ◽  
Protein A ◽  
Dna Helicase ◽  
Double Strand Breaks ◽  
Nuclear Bodies ◽  
H2ax Phosphorylation ◽  
Strand Breaks ◽  
Histone H2ax ◽  
Pml Nuclear Bodies ◽  
Atm Protein

ABSTRACT Topoisomerase I-associated DNA single-strand breaks selectively trapped by camptothecins are lethal after being converted to double-strand breaks by replication fork collisions. BLM (Bloom's syndrome protein), a RecQ DNA helicase, and topoisomerase IIIα (Top3α) appear essential for the resolution of stalled replication forks (Holliday junctions). We investigated the involvement of BLM in the signaling response to Top1-mediated replication DNA damage. In BLM-complemented cells, BLM colocalized with promyelocytic leukemia protein (PML) nuclear bodies and Top3α. Fibroblasts without BLM showed an increased sensitivity to camptothecin, enhanced formation of Top1-DNA complexes, and delayed histone H2AX phosphorylation (γ-H2AX). Camptothecin also induced nuclear relocalization of BLM, Top3α, and PML protein and replication-dependent phosphorylation of BLM on threonine 99 (T99p-BLM). T99p-BLM was also observed following replication stress induced by hydroxyurea. Ataxia telangiectasia mutated (ATM) protein and AT- and Rad9-related protein kinases, but not DNA-dependent protein kinase, appeared to play a redundant role in phosphorylating BLM. Following camptothecin treatment, T99p-BLM colocalized with γ-H2AX but not with Top3α or PML. Thus, BLM appears to dissociate from Top3α and PML following its phosphorylation and facilitates H2AX phosphorylation in response to replication double-strand breaks induced by Top1. A defect in γ-H2AX signaling in response to unrepaired replication-mediated double-strand breaks might, at least in part, explain the camptothecin-sensitivity of BLM-deficient cells.

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