scholarly journals Regulation of p53 by TopBP1: a Potential Mechanism for p53 Inactivation in Cancer

2009 ◽  
Vol 29 (10) ◽  
pp. 2673-2693 ◽  
Author(s):  
Kang Liu ◽  
Naresh Bellam ◽  
Hui-Yi Lin ◽  
Bing Wang ◽  
Cecil R. Stockard ◽  
...  
Keyword(s):  
Dna Damage ◽  
Target Genes ◽  
Tumor Grade ◽  
Binding Activity ◽  
Physiological Level ◽  
Cycle Arrest ◽  
P53 Target Gene ◽  
Induced Apoptosis ◽  
Cancer Tissues ◽  
P53 Inactivation

ABSTRACT Proper control of the G1/S checkpoint is essential for normal proliferation. The activity of p53 must be kept at a very low level under unstressed conditions to allow growth. Here we provide evidence supporting a crucial role for TopBP1 in actively repressing p53. Depletion of TopBP1 upregulates p53 target genes involved in cell cycle arrest and apoptosis and enhances DNA damage-induced apoptosis. The regulation is mediated by an interaction between the seventh and eighth BRCT domains of TopBP1 and the DNA-binding domain of p53, leading to inhibition of p53 promoter binding activity. Importantly, TopBP1 overexpression is found in 46 of 79 primary breast cancer tissues and is associated with high tumor grade and shorter patient survival time. Overexpression of TopBP1 to a level comparable to that seen in breast tumors leads to inhibition of p53 target gene expression and DNA damage-induced apoptosis and G1 arrest. Thus, a physiological level of TopBP1 is essential for normal G1/S transition, but a pathological level of TopBP1 in cancer may perturb p53 function and contribute to an aggressive tumor behavior.

scholarly journals Regulation of p53 by Hypoxia: Dissociation of Transcriptional Repression and Apoptosis from p53-Dependent Transactivation

2001 ◽  
Vol 21 (4) ◽  
pp. 1297-1310 ◽  
Author(s):  
Constantinos Koumenis ◽  
Rodolfo Alarcon ◽  
Ester Hammond ◽  
Patrick Sutphin ◽  
William Hoffman ◽  
...  
Keyword(s):  
Dna Damage ◽  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Target Genes ◽  
P53 Protein ◽  
Genotoxic Stress ◽  
Protein Accumulation ◽  
Dependent Cell ◽  
Apoptotic Activity ◽  
Induced Apoptosis

ABSTRACT Hypoxic stress, like DNA damage, induces p53 protein accumulation and p53-dependent apoptosis in oncogenically transformed cells. Unlike DNA damage, hypoxia does not induce p53-dependent cell cycle arrest, suggesting that p53 activity is differentially regulated by these two stresses. Here we report that hypoxia induces p53 protein accumulation, but in contrast to DNA damage, hypoxia fails to induce endogenous downstream p53 effector mRNAs and proteins. Hypoxia does not inhibit the induction of p53 target genes by ionizing radiation, indicating that p53-dependent transactivation requires a DNA damage-inducible signal that is lacking under hypoxic treatment alone. At the molecular level, DNA damage induces the interaction of p53 with the transcriptional activator p300 as well as with the transcriptional corepressor mSin3A. In contrast, hypoxia primarily induces an interaction of p53 with mSin3A, but not with p300. Pretreatment of cells with an inhibitor of histone deacetylases that relieves transcriptional repression resulted in a significant reduction of p53-dependent transrepression and hypoxia-induced apoptosis. These results led us to propose a model in which different cellular pools of p53 can modulate transcriptional activity through interactions with transcriptional coactivators or corepressors. Genotoxic stress induces both kinds of interactions, whereas stresses that lack a DNA damage component as exemplified by hypoxia primarily induce interaction with corepressors. However, inhibition of either type of interaction can result in diminished apoptotic activity.

scholarly journals Regulation of p53 Target Gene Expression by Peptidylarginine Deiminase 4

2008 ◽  
Vol 28 (15) ◽  
pp. 4745-4758 ◽  
Author(s):  
Pingxin Li ◽  
Hongjie Yao ◽  
Zhiqiang Zhang ◽  
Ming Li ◽  
Yuan Luo ◽  
...  
Keyword(s):  
Target Gene ◽  
Target Genes ◽  
Peptidylarginine Deiminase ◽  
Uv Treatment ◽  
Rna Pol Ii ◽  
Pol Ii ◽  
Cycle Arrest ◽  
P53 Target Gene ◽  
P53 Target Genes ◽  
P21 Promoter

ABSTRACT Histone Arg methylation has been correlated with transcriptional activation of p53 target genes. However, whether this modification is reversed to repress the expression of p53 target genes is unclear. Here, we report that peptidylarginine deiminase 4, a histone citrullination enzyme, is involved in the repression of p53 target genes. Inhibition or depletion of PAD4 elevated the expression of a subset of p53 target genes, including p21/CIP1/WAF1, leading to cell cycle arrest and apoptosis. Moreover, the induction of p21, cell cycle arrest, and apoptosis by PAD4 depletion is p53 dependent. Protein-protein interaction studies showed an interaction between p53 and PAD4. Chromatin immunoprecipitation assays showed that PAD4 is recruited to the p21 promoter in a p53-dependent manner. RNA polymerase II (Pol II) activities and the association of PAD4 are dynamically regulated at the p21 promoter during UV irradiation. Paused RNA Pol II and high levels of PAD4 were detected before UV treatment. At early time points after UV treatment, an increase of histone Arg methylation and a decrease of citrullination were correlated with a transient activation of p21. At later times after UV irradiation, a loss of RNA Pol II and an increase of PAD4 were detected at the p21 promoter. The dynamics of RNA Pol II activities after UV treatment were further corroborated by permanganate footprinting. Together, these results suggest a role of PAD4 in the regulation of p53 target gene expression.

DNA damage-induced [Zn2+]i transients: correlation with cell cycle arrest and apoptosis in lymphoma cells

2002 ◽  
Vol 283 (2) ◽  
pp. C609-C622 ◽  
Author(s):  
Paul J. Smith ◽  
Marie Wiltshire ◽  
Sharon Davies ◽  
Suet-Feung Chin ◽  
Anthony K. Campbell ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Arrest ◽  
Stress Responses ◽  
Damage Threshold ◽  
Lymphoma Cells ◽  
Cycle Arrest ◽  
Competent Cells ◽  
Drug Doses ◽  
Induced Apoptosis

Reactive changes in free intracellular zinc cation concentration ([Zn2+]i) were monitored, using the fluorescent probe Zinquin, in human lymphoma cells exposed to the DNA-damaging agent VP-16. Two-photon excitation microscopy showed that Zinquin-Zn2+ forms complexes in cytoplasmic vesicles. [Zn2+]iincreased in both p53wt (wild type) and p53mut(mutant) cells after exposure to low drug doses. In p53mutcells noncompetent for DNA damage-induced apoptosis, elevated [Zn2+]i was maintained at higher drug doses, unlike competent p53wt cells that showed a collapse of the transient before apoptosis. In p53wt cells, the [Zn2+]i rise paralleled an increase in p53 and bax-to-bcl-2 ratio but preceded an increase in p21WAF1, active cell cycle arrest in G2, or nuclear fragmentation. Reducing [Zn2+]i, using N, N, N′, N′-tetrakis(2-pyridylmethyl)ethylenediamine, caused rapid apoptosis in both p53wt and p53mut cells, although cotreatment with VP-16 exacerbated apoptosis only in p53wt cells. This may reflect changed thresholds for proapoptotic caspase-3 activation in competent cells. We conclude that the DNA damage-induced transient is p53-independent up to a damage threshold, beyond which competent cells reduce [Zn2+]i before apoptosis. Early stress responses in p53wt cells take place in an environment of enhanced Zn2+ availability.

scholarly journals Deregulation of DNA Damage Signal Transduction by Herpesvirus Latency-Associated M2

2006 ◽  
Vol 80 (12) ◽  
pp. 5862-5874 ◽  
Author(s):  
Xiaozhen Liang ◽  
Mary T. Pickering ◽  
Nam-Hyuk Cho ◽  
Heesoon Chang ◽  
Michael R. Volkert ◽  
...  
Keyword(s):  
Dna Damage ◽  
Immune Surveillance ◽  
Atm Kinase ◽  
Kinase Activation ◽  
Cycle Arrest ◽  
Damage Response ◽  
Gamma Herpesvirus ◽  
Infected Cells ◽  
Induced Apoptosis ◽  
Host Immune Surveillance

ABSTRACT Infected cells recognize viral replication as a DNA damage stress and elicit a DNA damage response that ultimately induces apoptosis as part of host immune surveillance. Here, we demonstrate a novel mechanism where the murine gamma herpesvirus 68 (γHV68) latency-associated, anti-interferon M2 protein inhibits DNA damage-induced apoptosis by interacting with the DDB1/COP9/cullin repair complex and the ATM DNA damage signal transducer. M2 expression constitutively induced DDB1 nuclear localization and ATM kinase activation in the absence of DNA damage. Activated ATM subsequently induced Chk activation and p53 phosphorylation and stabilization without eliciting H2AX phosphorylation and MRN recruitment to foci upon DNA damage. Consequently, M2 expression inhibited DNA repair, rendered cells resistant to DNA damage-induced apoptosis, and induced a G1 cell cycle arrest. Our results suggest that γHV68 M2 blocks apoptosis-mediated intracellular innate immunity, which might ultimately contribute to its role in latent infection.

Sevoflurane Inhibits Growth and Metastasis of Cervical Cancer Through Up-Regulating miR-203 by Targeting Tumor Protein Translationally Controlled 1

2020 ◽  
Vol 10 (6) ◽  
pp. 874-883
Author(s):  
Li Zhang ◽  
Shiyou Wei ◽  
Zhenkai Xu ◽  
Wen Sun ◽  
Lihua Hang
Keyword(s):  
Cervical Cancer ◽  
Cell Viability ◽  
Cancer Cells ◽  
Target Genes ◽  
Luciferase Reporter ◽  
Migration And Invasion ◽  
Reporter System ◽  
Cervical Cancer Cells ◽  
Induced Apoptosis ◽  
Cancer Tissues

Background: Cervical cancer is a type of malignancy with high incidence and high mortality in women all over the world. Recent findings revealed the role of sevoflurane in the inhibition of development of various cancer types. This study aimed to explore whether sevoflurane could suppress cells proliferation and metastasis through adjusting miR-203 expression in cervical cancer. Methods: The effects of sevoflurane on HeLa cell viability was assessed using CCK-8 assay. miR-203 level in Hela cells was determined by qRT-PCR. In addition, cells apoptosis, migration and invasion were evaluated using flow cytometry and transwell analysis respectively after sevoflurane treatment or miR-203 expression changes. Bioinformatics software (TargetScan) was used to predict the potential target genes for miR-203 and the prediction was validated using dual-luciferase reporter system. Results: Sevoflurane effectively inhibited cell viability, metastasis and stimulated apoptosis in cervical cancer. miR-203 demonstrated a low expression in cervical cancer tissues and cells and sevoflurane significantly up-regulated miR-203 expression in cervical cancer cells. Upregulation of miR-203 significantly suppressed cell growth and metastasis and induced apoptosis, while down-regulation of miR-203 presented the opposite effects in cervical cancer cells. In addition, the inhibitory effects of sevoflurane were eliminated by down-regulating miR-203 in cervical cancer cells. In addition, TPT1 was confirmed as a target gene for miR-203. Conclusion: Sevoflurane inhibited cervical cancer cells viability and metastasis through up-regulation of miR-203 expression by targeting TPT1.

scholarly journals BH3-only proteins Puma and Bim are rate-limiting for γ-radiation– and glucocorticoid-induced apoptosis of lymphoid cells in vivo

Blood ◽  
2005 ◽  
Vol 106 (13) ◽  
pp. 4131-4138 ◽  
Author(s):  
Miriam Erlacher ◽  
Ewa M. Michalak ◽  
Priscilla N. Kelly ◽  
Verena Labi ◽  
Harald Niederegger ◽  
...  
Keyword(s):  
Dna Damage ◽  
Target Genes ◽  
Cultured Cells ◽  
Lymphoid Cells ◽  
Whole Body ◽  
Γ Radiation ◽  
B Cell Leukemia ◽  
Induced Apoptosis

Numerous p53 target genes have been implicated in DNA damage–induced apoptosis signaling, but proapoptotic Bcl-2 (B-cell leukemia 2) family members of the BH3 (Bcl-2 homolog region [BH] 3)–only subgroup appear to play the critical initiating role. In various types of cultured cells, 3 BH3-only proteins, namely Puma (p53 up-regulated modulator of apoptosis), Noxa, and Bim (Bcl-2 interacting mediator of cell death), have been shown to initiate p53-dependent as well as p53-independent apoptosis in response to DNA damage and treatment with anticancer drugs or glucocorticoids. In particular, the absence of Puma or Bim renders thymocytes and mature lymphocytes refractory to varying degrees to death induced in vitro by growth factor withdrawal, DNA damage, or glucocorticoids. To assess the in vivo relevance of these findings, we subjected mice lacking Puma, Noxa, or Bim to whole-body γ-radiation or the glucocorticoid dexamethasone and compared lymphocyte survival with that in wild-type and BCL2–transgenic mice. Absence of Puma or Bcl-2 overexpression efficiently protected diverse types of lymphocytes from the effects of γ-radiation in vivo, and loss of Bim provided lower but significant protection in most lymphocytes, whereas Noxa deficiency had no impact. Furthermore, both Puma and Bim were found to contribute significantly to glucocorticoid-induced killing. Our results thus establish that Puma and Bim are key initiators of γ-radiation– and glucocorticoid-induced apoptosis in lymphoid cells in vivo.

Cadmium-induced DNA damage triggers G2/M arrest via chk1/2 and cdc2 in p53-deficient kidney proximal tubule cells

2010 ◽  
Vol 298 (2) ◽  
pp. F255-F265 ◽  
Author(s):  
Ulrich Bork ◽  
Wing-Kee Lee ◽  
Anna Kuchler ◽  
Thomas Dittmar ◽  
Frank Thévenod
Keyword(s):  
Dna Damage ◽  
Proximal Tubule ◽  
Ataxia Telangiectasia ◽  
Kinase Inhibitor ◽  
M Cell ◽  
Kidney Proximal Tubule ◽  
Cycle Arrest ◽  
Class 1 ◽  
Multistep Process ◽  
P53 Inactivation

Carcinogenesis is a multistep process that is frequently associated with p53 inactivation. The class 1 carcinogen cadmium (Cd2+) causes renal cancer and is known to inactivate p53. G2/mitosis (M) arrest contributes to stabilization of p53-deficient mutated cells, but its role and regulation in Cd2+-exposed p53-deficient renal cells are unknown. In p53-inactivated kidney proximal tubule (PT) cells, comet assay experiments showed that Cd2+ (50–100 μM) induced DNA damage within 1–6 h. This was associated with peak formation of reactive oxygen species (ROS) at 1–3 h, measured with dihydrorhodamine 123, and G2/M cell cycle arrest at 6 h, which were abolished by the antioxidant α-tocopherol (100 μM). Cd2+-induced G2/M arrest was enhanced approximately twofold on release from cell synchronization (double thymidine block or nocodazole) and resulted in approximately twofold increase of apoptosis, indicating that G2/M arrest mirrors DNA damage and toxicity. The Chk1/2 kinase inhibitor UCN-01 (0.3 μM), which relieves G2/M transition block, abolished Cd2+-induced G2 arrest and increased apoptosis. This was accompanied by prevention of Cd2+-induced cyclin-dependent kinase cdc2 phosphorylation at tyrosine 15, as shown by immunofluorescence microscopy and immunoblotting. The data indicate that in p53-inactivated PT cells Cd2+-induced ROS formation and DNA damage trigger signaling of checkpoint activating kinases ataxia telangiectasia-mutated kinase (ATM) and ataxia telangiectasia and Rad3-related kinase (ATR) to cause G2/M arrest. This may promote survival of premalignant PT cells and Cd2+ carcinogenesis.

scholarly journals Mammalian PER2 regulates AKT activation and DNA damage response

2012 ◽  
Vol 90 (6) ◽  
pp. 675-682 ◽  
Author(s):  
Xiaoming Yang ◽  
Xuezhong He ◽  
Zhengguan Yang ◽  
Esmaiel Jabbari
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Damage Response ◽  
Down Regulation ◽  
Akt Activation ◽  
Cycle Arrest ◽  
Damage Response ◽  
Induced Apoptosis ◽  
Tumor Suppressive Function ◽  
Clock Protein

PER2 is a key mammalian circadian clock protein. It also has a tumor suppressive function. Down regulation of PER2 in the cultured cancer cells accelerates cell proliferation, while overexpression of PER2 inhibits cell growth and induces apoptosis. The Per2 mutant mice have a cancer prone phenotype and an altered DNA damage response. Here we report that PER2 regulates AKT activity. Cells with down-regulated PER2 expression have prolonged high levels of AKT T308 phosphorylation after growth factor stimulation or DNA damage. PER2 down-regulation delays DNA damage induced Chk2 activation and overrides DNA damage induced apoptosis and cell cycle arrest.

The Dichloromethane Fraction of Vernonia cinerea Impart Pro-Apoptotic, Genotoxic, Cell Cycle Arrest, and Drug Efflux Inhibitory Effects on Human Adenocarcinoma Cells

2020 ◽  
Vol 15 (3) ◽  
pp. 239-256
Author(s):  
Asmy Appadath Beeran ◽  
Nayanabhirama Udupa ◽  
Naseer Maliyakkal
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Epithelial Cells ◽  
Anticancer Drugs ◽  
Functional Activity ◽  
Cytotoxic Effects ◽  
Cycle Arrest ◽  
Adenocarcinoma Cells ◽  
Induced Apoptosis ◽  
Vernonia Cinerea

Background: Vernonia cinerea (VC) is an important medicinal plant used in the indigenous system of therapy. In ethnomedicine, VC has demonstrated anticancer properties. However, the mechanisms of action VC is not known. Objective: To establish the anticancer mechanisms of ‘bioactive fractions of VC’ on human adenocarcinoma cells. Methods: The IC50 values of characterized VC extract and fractions in human adenocarcinoma and normal epithelial cells were determined using Sulforhodamine B (SRB) assay. Acridine Orange- Ethidium Bromide (AO-EB) assay/Hoechst 33342 assay, Comet assay, and Cell cycle analysis were used to determine apoptosis, genotoxicity, and cell cycle-specific changes in cancer cells, respectively. Rhodamine 123 (Rho-123) efflux assay and Mitoxantrone (MX) efflux assay were used to assess the inhibition of Multidrug Resistance (MDR) transporters. Results: The dichloromethane fraction of VC (VC-DM) imparted dose-dependent cytotoxicity in human adenocarcinoma cells with fewer effects in human normal epithelial cells. This ‘sesquiterpenoids’ enriched fraction (VC-DM) induced apoptosis, DNA damage, genotoxicity, and G2/M phase arrest in human adenocarcinoma cells. Interestingly, VC-DM significantly inhibited the functional activity of MDR transporters (ABCB1 and ABCG2) and caused ‘synergistic cytotoxic effects’ with anticancer drugs in human adenocarcinoma cells. Conclusion: The bioactivity guided fractionation of VC revealed that the specific ‘sesquiterpenoids enriched fraction’ (VC-DM) imparted cytotoxicity in human adenocarcinoma cells with fewer effects on normal cells. Mechanistic studies have shown that VC-DM induced apoptosis, DNA damage, genotoxicity, cell cycle arrest (G2/M), inhibited the functional activity of MDR transporters (ABCB1 and ABCG2), and produced ‘synergistic cytotoxic effects’ (combinatorial treatments with anticancer drugs) in human adenocarcinoma cells. Taken together, the findings of this study emphasize and validates VC-DM as a promising ‘anticancer agent’ against human adenocarcinomas, including those with a multi-drug resistant phenotype.

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