scholarly journals Inhibition of PIM Kinases Mitigates DNA Repair Responses Following Anthracycline-Induced DNA Damage and Enhances the Anti-Tumor Activity of Doxorubicin Against Lymphoma Cells

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4505-4505 ◽  
Author(s):  
Jeffrey D. Altenburg ◽  
Shuhong Zhang ◽  
Michelle Grimard ◽  
Xingkui Xue ◽  
Sherif S Farag
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Death ◽  
Dna Repair ◽  
Cell Growth ◽  
Cell Lines ◽  
Cell Cycle Progression ◽  
Fold Increase ◽  
Pim Kinases ◽  
Anti Cancer

Abstract The PIM kinases are a family of proteins recently identified as promising therapeutic targets in several cancers, including pancreatic, B-cell malignancies, acute leukemia, and prostate cancer among others. The family of PIM kinases is composed of three different members (PIM-1, -2, and -3) that are short-lived serine/threonine kinases involved in the regulation of a number of cellular pathways that are important for cancer cell growth and survival. The PIM kinases show high homology with each other, and exhibit functional redundancy in vitro and in vivo. Overexpression of PIM kinases promotes tumor growth through activation of several key cell-cycle progression and anti-apoptotic proteins, including BAD, p21, p27KIP, c-Myc, and AKT-1. Recently, overexpression of PIM-2 has been shown to have a protective effect against ultraviolet light induced DNA damage (Zirkin et al. J Biol Chem288:21770-83, 2013). We investigated the protective role of PIM kinases in chemotherapy-induced DNA damage, and whether inhibition of PIM kinases enhances anthracycline-induced DNA damage by inhibiting DNA repair, thus enhancing cell death in lymphoma cells lines. Using immunobloting and RT-PCR, we found similarly low levels of PIM-1 and PIM-3, but a wide range of PIM-2 expression, in a panel of non-Hodgkin lymphoma (NHL) cell lines, including Raji, HS Sultan, Daudi, Farage, Granta519, and Toledo. Treatment of cells with doxorubicin (200-400 nM) resulted in up to a five fold increase gene transcription and expression of PIM-1 and PIM-2, which was maximal at 6 hours, and was associated with an increase in DNA damage as detected using acridine orange flow cytometry assay. We also tested the single agent effect of the pan-PIM kinase inhibitor, CX6258 on the cell lines. CX6258 alone inhibited cell growth in all NHL cell lines with varying degrees of potency with IC50ranging from 0.2 – 12.9 µM. The anti-cancer was associated most with PIM-2 expression, with the most sensitive cell lines, Daudi and Toledo, expressing the most PIM-2. Suppression of PIM-2 expression by shRNA significantly decreased proliferation, indicating that PIM-2 is a significant factor in cell growth. Treatment of NHL cells with CX6258 resulted in increased caspase-3 activation and PARP cleavage, decreased BAD phosphorylation, and apoptosis. Treatment with CX6258 also increased expression of p21, decreased expression of cyclins A1 and B1, and induced G2-M cell cycle arrest. The effect of combinations of CX6258 (5-50 µM) and doxorubicin (50-500 nM) on DNA damage and cell death was tested on HS sultan and Daudi cells. While doxorubicin alone resulted in a two-fold increase in DNA damage, this was significantly increased in the presence of CX6258 (12 fold). The addition of CX6258 inhibited the phosphorylation of the DNA repair proteins H2.AX, ATM, and Chk2 that occurred when the cells were treated with doxorubicin alone. The combination of CX6258 and doxorubicin was synergistic in inducing lymphoma cell death, with combination indexes ranging from 0.32-0.85. Our findings suggest a mechanism for synergy where doxorubicin damages cellular DNA and initiates the DNA damage response, while CX6258 inhibits the upregulated PIM kinases from activating the proteins involved in the response. This synergistic anti-tumor activity is further strengthened by the CX6258 inhibition of cell cycle progression and anti-apoptotic proteins activated by the PIM kinases. Taken together, our results provide pre-clinical rationale for clinical testing of PIM kinase inhibitors in combination with doxorubicin in patients with NHL. It also suggests that CX6258 may similarly enhance the anti-cancer effects of other DNA damaging agents. Disclosures No relevant conflicts of interest to declare.

scholarly journals Dysregulation of hsa-miR-34a and hsa-miR-449a leads to overexpression of PACS-1 and loss of DNA damage response (DDR) in cervical cancer

2020 ◽  
Vol 295 (50) ◽  
pp. 17169-17186
Author(s):  
Mysore S. Veena ◽  
Santanu Raychaudhuri ◽  
Saroj K. Basak ◽  
Natarajan Venkatesan ◽  
Parameet Kumar ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cervical Cancer ◽  
Dna Damage ◽  
Cell Growth ◽  
Cell Lines ◽  
Cancer Cell ◽  
Dna Damage Response ◽  
S Phase ◽  
Cervical Cancer Cell ◽  
Damage Response

We have observed overexpression of PACS-1, a cytosolic sorting protein in primary cervical tumors. Absence of exonic mutations and overexpression at the RNA level suggested a transcriptional and/or posttranscriptional regulation. University of California Santa Cruz genome browser analysis of PACS-1 micro RNAs (miR), revealed two 8-base target sequences at the 3′ terminus for hsa-miR-34a and hsa-miR-449a. Quantitative RT-PCR and Northern blotting studies showed reduced or loss of expression of the two microRNAs in cervical cancer cell lines and primary tumors, indicating dysregulation of these two microRNAs in cervical cancer. Loss of PACS-1 with siRNA or exogenous expression of hsa-miR-34a or hsa-miR-449a in HeLa and SiHa cervical cancer cell lines resulted in DNA damage response, S-phase cell cycle arrest, and reduction in cell growth. Furthermore, the siRNA studies showed that loss of PACS-1 expression was accompanied by increased nuclear γH2AX expression, Lys382-p53 acetylation, and genomic instability. PACS-1 re-expression through LNA-hsa-anti-miR-34a or -449a or through PACS-1 cDNA transfection led to the reversal of DNA damage response and restoration of cell growth. Release of cells post 24-h serum starvation showed PACS-1 nuclear localization at G1-S phase of the cell cycle. Our results therefore indicate that the loss of hsa-miR-34a and hsa-miR-449a expression in cervical cancer leads to overexpression of PACS-1 and suppression of DNA damage response, resulting in the development of chemo-resistant tumors.

scholarly journals Anticancer Activity of Cynomorium coccineum

Cancers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 354 ◽  
Author(s):  
Mouna Sdiri ◽  
Xiangmin Li ◽  
William Du ◽  
Safia El-Bok ◽  
Yi-Zhen Xie ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Anticancer Activity ◽  
Cancer Cells ◽  
Cell Lines ◽  
Cancer Cell ◽  
Cell Cycle Progression ◽  
Cycle Progression

The extensive applications of Cynomorium species and their rich bioactive secondary metabolites have inspired many pharmacological investigations. Previous research has been conducted to examine the biological activities and numerous interesting pharmaceutical activities have been reported. However, the antitumor activities of these species are unclear. To understand the potential anticancer activity, we screened Cynomorium coccineum and Cynomorium songaricum using three different extracts of each species. In this study, the selected extracts were evaluated for their ability to decrease survival rates of five different cancer cell lines. We compared the cytotoxicity of the three different extracts to the anticancer drug vinblastine and one of the most well-known medicinal mushrooms Amaurederma rude. We found that the water and alcohol extracts of C. coccineum at the very low concentrations possessed very high capacity in decreasing the cancer cells viability with a potential inhibition of tumorigenesis. Based on these primitive data, we subsequently tested the ethanol and the water extracts of C. coccineum, respectively in in vitro and in vivo assays. Cell cycle progression and induction of programmed cell death were investigated at both biological and molecular levels to understand the mechanism of the antitumor inhibitory action of the C. coccineum. The in vitro experiments showed that the treated cancer cells formed fewer and smaller colonies than the untreated cells. Cell cycle progression was inhibited, and the ethanol extract of C. coccineum at a low concentration induced accumulation of cells in the G1 phase. We also found that the C. coccineum’s extracts suppressed viability of two murine cancer cell lines. In the in vivo experiments, we injected mice with murine cancer cell line B16, followed by peritoneal injection of the water extract. The treatment prolonged mouse survival significantly. The tumors grew at a slower rate than the control. Down-regulation of c-myc expression appeared to be associated with these effects. Further investigation showed that treatment with C. coccineum induced the overexpression of the tumor suppressor Foxo3 and other molecules involved in inducing autophagy. These results showed that the C. coccineum extract exerts its antiproliferative activity through the induction of cell death pathway. Thus, the Cynomorium plants appear to be a promising source of new antineoplastic compounds.

Abstract C46: DNA damage-induced autophagy is required for efficient DNA repair and cell cycle progression

2012 ◽  
Vol 72 (4 Supplement) ◽  
pp. C46-C46
Author(s):  
Kamini Singh ◽  
Sayer R. Al-Harbi ◽  
Akwasi Agyeman ◽  
Janet A. Houghton ◽  
Warren D. Heston ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Repair ◽  
Cell Cycle Progression ◽  
Cycle Progression

scholarly journals Cellular responses to a prolonged delay in mitosis are determined by a DNA damage response controlled by Bcl-2 family proteins

Open Biology ◽  
2015 ◽  
Vol 5 (3) ◽  
pp. 140156 ◽  
Author(s):  
Didier J. Colin ◽  
Karolina O. Hain ◽  
Lindsey A. Allan ◽  
Paul R. Clarke
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Protein Kinases ◽  
Cell Fate ◽  
Dna Damage Response ◽  
Cell Cycle Progression ◽  
Cycle Progression ◽  
Anti Cancer ◽  
Damage Response ◽  
Microtubule Poisons

Anti-cancer drugs that disrupt mitosis inhibit cell proliferation and induce apoptosis, although the mechanisms of these responses are poorly understood. Here, we characterize a mitotic stress response that determines cell fate in response to microtubule poisons. We show that mitotic arrest induced by these drugs produces a temporally controlled DNA damage response (DDR) characterized by the caspase-dependent formation of γH2AX foci in non-apoptotic cells. Following exit from a delayed mitosis, this initial response results in activation of DDR protein kinases, phosphorylation of the tumour suppressor p53 and a delay in subsequent cell cycle progression. We show that this response is controlled by Mcl-1, a regulator of caspase activation that becomes degraded during mitotic arrest. Chemical inhibition of Mcl-1 and the related proteins Bcl-2 and Bcl-x L by a BH3 mimetic enhances the mitotic DDR, promotes p53 activation and inhibits subsequent cell cycle progression. We also show that inhibitors of DDR protein kinases as well as BH3 mimetics promote apoptosis synergistically with taxol (paclitaxel) in a variety of cancer cell lines. Our work demonstrates the role of mitotic DNA damage responses in determining cell fate in response to microtubule poisons and BH3 mimetics, providing a rationale for anti-cancer combination chemotherapies.

Preclinical Efficacy and Biological Effects of Venetoclax and Ixazomib in Combination in Lymphoma Cells

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 37-38
Author(s):  
Maria Cosenza ◽  
Stefano Sacchi ◽  
Samantha Pozzi
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Cell Growth ◽  
Cell Lines ◽  
Stromal Cells ◽  
Biological Effects ◽  
Lymphoma Cell ◽  
Lymphoma Cells ◽  
Induction Of Apoptosis ◽  
Preclinical Efficacy

Introduction. Bcl-2 family proteins comprise anti-apoptotic and pro-apoptotic proteins. Interaction between these proteins, as well as severe regulation of their expression, mediates cell survival and can quickly induce cell death. Venetoclax is Bcl-2-targeting that has shown preclinical and clinical activity in hematologic malignancies. Due to the development of resistance and the loss of dependence on the target protein, the monotherapy may be insufficient for maximal effectiveness. To circumvent the resistance mechanisms, many preclinical studies have shown that combination of venetoclax with other agents may represent a more effective therapeutic strategy. Ubiquitin-proteasome signaling pathway is a potential target that plays an important role in the proteolysis of key regulatory proteins. Proteasome inhibitors include ixazomib that inhibits cell growth and induces apoptosis in hematological malignancies cells resistant to conventional therapies and bortezomib. Objective: To analyze the preclinical efficacy and associated biological effects of venetoclax combined with ixazomib in a panel of lymphoma cell lines with diverse expression levels of Bcl-2 and other Bcl-2 family proteins. Methods: 12 lymphoma cell lines including FL (RL, WSU-NHL, Karpas422), MCL (Jeko1, Granta519), DLBCL (OCI-LY3, OCI-LY18), CTCL (Hut-78), ALCL (Karpas299), HL (L1236, L540), CLL (Mec1) and two MCL primary patient samples were exposed to venetoclax (0.01 - 8 µM) and ixazomib (10 - 2000 nM) alone for 24 - 72 hours to calculate IC50. Subsequently, lymphoma cells were exposed to venetoclax (0.015 - 25 nM) in combination with ixazomib (0.015 - 0.5 nM) for 24 hours. Cell viability was determined by MTT. Coefficient of synergy (combination index - CI) was calculated using CalcuSyn. Cell cycle and induction of apoptosis were evaluated by flow cytometry and changes in Bcl-2 family members, caspase activation and AKT phosphorylation were determined by western blotting. Results. In vitro, venetoclax and ixazomib alone induced cell death in a dose- and time-dependent manner against lymphoma cell lines. The IC50 is between 0.5 and 8 µM for venetoclax and between 12 and 1250 nM for ixazomib. The combination of venetoclax (0.03, 0.06, 12.5, 25 nM) with ixazomib (0.03, 0.06, 0.25, 0.5 nM) produced a synergistic effect (CI < 1) after 24 h of treatment in the most lymphoma cells lines leading to inhibition of cell growth and induction of apoptosis between 26 % and 59 % accompanied by increased with cleavage of caspases-3, -9 and PARP. We observed an additive effect (CI = 1) in Jeko1 (MCL) and MEC1 cells (CLL) and antagonist effect (CI > 1) Hut-78 cells (CTCL). Synergistic effect has been seen in two MCL primary patient samples (CI = 0.5 - 0.7). In sensitive lymphoma cells, the combination abrogated colony formation in the methylcellulose medium. When lymphoma cell lines were co-cultured with mesenchymal stromal cells with both drugs we observed a decrease of cell viability and a fraction of apoptotic cells indicating that drug combination may overcome the tumor promoting effects of stromal cells. The apoptosis induced in FL and Granta519 cells (MCL) by drug combination was accompanied by partial downregulation of Bcl-2 and strong upregulation of Bax, Bad, Bim and Noxa proteins. Jeko-1 cells were less sensitive to venetoclax-ixazomib combination-induced apoptosis. Western blot analysis showed a differential expression of Bcl-2, Mcl-1 and Bcl-XL proteins in FL, MCL and HL cell lines. Jeko-1 cells showed a normal expression of Bcl-2 and Mcl-1 proteins and high Bcl-xL protein level. Co-expression of related anti-apoptotic Bcl-2 family proteins could limit activity of treatment. Combined treatment induced G0/G1 cell cycle arrest and increased the sub-G1 population that was linked by the upregulation of p27 and p21. In addition, in RL, WSU-NHL and Granta519, enhanced cell death is associated with AKT inactivation and with a reduction of p-4EBP1, leading to decreased levels of c-MYC. Conclusion. Venetoclax exhibits strong synergistic activity with ixazomib in lymphoma cells. Studies are still ongoing and signaling pathways that promote the combination of venetoclax with ixazomib are to be analyzed. These data offer a rationale to continue exploring venetoclax-ixazomib combination and suggest that suppression of Bcl-2 family protein driven survival signaling may be one important mechanism for combination synergy. Disclosures No relevant conflicts of interest to declare.

The mTOR Inhibitor Everolimus Overcomes CXCR4-Mediated Resistance to HDAC Inhibitor Panobinostat through Inhibition of p21 and Mitosis Regulators, Sensitizing MM Cells to DNA-Damaged Induced Apoptosis

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 891-891
Author(s):  
Katia Beider ◽  
Valeria Voevoda ◽  
Hanna Bitner ◽  
Evgenia Rosenberg ◽  
Hila Magen ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Death ◽  
Dna Repair ◽  
Cell Lines ◽  
Hdac Inhibitor ◽  
Mtor Inhibitor ◽  
Mtor Inhibition ◽  
Induced Apoptosis

Abstract Introduction: Multiple myeloma (MM) is a neoplastic disorder that is characterized by clonal proliferation of plasma cells in the bone marrow (BM). Despite the initial efficacious treatment, MM patients often become refractory to common anti-MM drugs, therefore novel therapies are in need. Pan-histone deacetylase (HDAC) inhibitor panobinostat exerts multiple cytotoxic actions in MM cells in vitro, and was approved for the treatment of relapsed/refractory MM in combination with bortezomib and dexamethasone. Although having promising anti-MM properties, panobinostat lacks therapeutic activity as monotherapy. The aim of the current study was to elucidate the mechanisms underlying MM resistance to panobinostat and to define strategies to overcome it. Results: Panobinostat at the low concentrations (IC50 5-30 nM) suppressed the viability in MM cell lines (n=7) and primary CD138+ cells from MM patients (n=8) in vitro. Sensitivity to panobinostat correlated with reduced expression of chemokine receptor CXCR4, while overexpression of CXCR4 or its ligand CXCL12 in RPMI8226 and CAG MM cell lines significantly (p<0.001) increased their resistance to panobinostat, pointing to the role of the CXCR4 axis in HDACi response. Notably, similar expression levels of class I HDACs (HDAC1-3) were detected in MM cells with either low or high CXCR4. Interaction with BM stromal cells that represent the source of CXCL12 also protected MM cells from panobinostat-induced apoptosis, further strengthening a role for CXCR4 downstream pathway. Decreased sensitivity to cytotoxic effect was concomitant with reduced histone (H3K9 and H4K8) acetylation in response to panobinostat treatment. In addition, resistance to HDACi was associated with the reversible G0/G1 cell growth arrest, whereas sensitivity was characterized by apoptotic cell death. Analysis of intra-cellular signaling mediators involved in CXCR4-mediated HDACi resistance revealed the pro-survival AKT/mTOR pathway to be regulated by both CXCR4 over-expression and interaction with BMSCs. Combining panobinostat with mTOR inhibitor everolimus abrogated the resistance and induced synergistic cell death of MM cell lines and primary MM cells, but not of normal mononuclear cells (CI<0.4). This effect was concurrent with the increase in DNA double strand breaks, histone H2AX phosphorylation, loss of Dψm, cytochrome c release, caspase 3 activation and PARP cleavage. The increase in DNA damage upon combinational treatment was not secondary to the apoptotic DNA fragmentation, as it occurred similarly when apoptosis onset was blocked by caspase inhibitor z-VAD-fmk. Kinetics studies also confirmed that panobinostat-induced DNA damage preceded apoptosis induction. Strikingly, combined panobinostat/everolimus treatment resulted in sustained DNA damage and irreversible suppression of MM cell proliferation accompanied by robust apoptosis, in contrast to the modest effects induced by single agent. Gene expression analysis revealed distinct genetic profiles of single versus combined exposures. Whereas panobinostat increased the expression of cell cycle inhibitors GADD45G and p21, co-treatment with everolimus abrogated the increase in p21 and synergistically downregulated DNA repair genes, including RAD21, Ku70, Ku80 and DNA-PKcs. Furthermore, combined treatment markedly decreased both mRNA and protein expression of anti-apoptotic factors survivin and BCL-XL, checkpoint regulator CHK1, and G2/M-specific factors PLK1, CDK1 and cyclin B1, therefore suppressing the DNA damage repair and inhibiting mitotic progression. Given the anti-apoptotic role of p21, the synergistic lethal effect of everolimus could be attributed to its ability to suppress p21 induction by panobinostat ensuing the shift in the DNA damage response toward apoptosis. Conclusions: Collectively, our findings indicate that CXCR4/CXCL12 activity promotes the resistance of MM cells to HDACi with panobinostat through mTOR activation. Inhibition of mTOR by everolimus synergizes with panobinostat by simultaneous suppression of p21, G2/M mitotic factors and DNA repair machinery, rendering MM cells incapable of repairing accumulated DNA damage and promoting their apoptosis. Our results unravel the mechanism responsible for strong synergistic anti-MM activity of dual HDAC and mTOR inhibition and provide the rationale for a novel therapeutic strategy to eradicate MM. Disclosures No relevant conflicts of interest to declare.

scholarly journals Effect of combined DNA repair inhibition and G2 checkpoint inhibition on cell cycle progression after DNA damage

2006 ◽  
Vol 5 (4) ◽  
pp. 885-892 ◽  
Author(s):  
Christopher M. Sturgeon ◽  
Zachary A. Knight ◽  
Kevan M. Shokat ◽  
Michel Roberge
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Repair ◽  
Cell Cycle Progression ◽  
Checkpoint Inhibition ◽  
Cycle Progression ◽  
G2 Checkpoint

scholarly journals A fission yeast homolog of CDC20/p55CDC/Fizzy is required for recovery from DNA damage and genetically interacts with p34cdc2.

1997 ◽  
Vol 17 (2) ◽  
pp. 742-750 ◽  
Author(s):  
T Matsumoto
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Repair ◽  
Fission Yeast ◽  
Cell Cycle Progression ◽  
Eukaryotic Cell ◽  
Cycle Progression ◽  
Cell Cycle Delay ◽  
Successful Recovery ◽  
Synthetically Lethal

Successful recovery from DNA damage requires coordination of several biological processes. Eukaryotic cell cycle progression is delayed when the cells encounter DNA-damaging agents. This cell cycle delay allows the cells to cope with DNA damage by utilizing DNA repair enzymes. Thus, at least two processes, induction of the cell cycle delay and repair of damaged DNA, are coordinately required for recovery. In this study, a fission yeast rad mutant (slp1-362) was genetically investigated. In response to radiation, slp1 stops cell division; however, it does not restart it. This defect is suppressed when slp1-362 is combined with wee1-50 or cdc2-3w; in these mutants, the onset of mitosis is advanced due to the premature activation of p34cdc2. In contrast, slp1 is synthetically lethal with cdc25, nim1/cdr1, or cdr2, all of which are unable to activate the p34cdc2 kinase correctly. These genetic interactions of slp1 with cdc2 and its modulators imply that slp1 is not defective in either "induction of cell cycle delay" or "DNA repair." slp1+ may be involved in a critical process which restarts cell cycle progression after the completion of DNA repair. Molecular cloning of slp1+ revealed that slp1+ encodes a putative 488-amino-acid polypeptide exhibiting significant homology to WD-domain proteins, namely, CDC20 (budding yeast), p55CDC (human), and Fizzy (fly). A possible role of slp1+ is proposed.

scholarly journals The chromatin-remodeling factor CHD4 coordinates signaling and repair after DNA damage

2010 ◽  
Vol 190 (5) ◽  
pp. 731-740 ◽  
Author(s):  
Dorthe Helena Larsen ◽  
Catherine Poinsignon ◽  
Thorkell Gudjonsson ◽  
Christoffel Dinant ◽  
Mark R. Payne ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Repair ◽  
Chromatin Remodeling ◽  
Cell Cycle Progression ◽  
Clonogenic Survival ◽  
Dna Double Strand Breaks ◽  
Checkpoint Signaling ◽  
Strand Breaks ◽  
Delay Cell

In response to ionizing radiation (IR), cells delay cell cycle progression and activate DNA repair. Both processes are vital for genome integrity, but the mechanisms involved in their coordination are not fully understood. In a mass spectrometry screen, we identified the adenosine triphosphate–dependent chromatin-remodeling protein CHD4 (chromodomain helicase DNA-binding protein 4) as a factor that becomes transiently immobilized on chromatin after IR. Knockdown of CHD4 triggers enhanced Cdc25A degradation and p21Cip1 accumulation, which lead to more pronounced cyclin-dependent kinase inhibition and extended cell cycle delay. At DNA double-strand breaks, depletion of CHD4 disrupts the chromatin response at the level of the RNF168 ubiquitin ligase, which in turn impairs local ubiquitylation and BRCA1 assembly. These cell cycle and chromatin defects are accompanied by elevated spontaneous and IR-induced DNA breakage, reduced efficiency of DNA repair, and decreased clonogenic survival. Thus, CHD4 emerges as a novel genome caretaker and a factor that facilitates both checkpoint signaling and repair events after DNA damage.

scholarly journals RCC1-dependent activation of Ran accelerates cell cycle and DNA repair, inhibiting DNA damage–induced cell senescence

2016 ◽  
Vol 27 (8) ◽  
pp. 1346-1357 ◽  
Author(s):  
Pavol Cekan ◽  
Keisuke Hasegawa ◽  
Yu Pan ◽  
Emily Tubman ◽  
David Odde ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Repair ◽  
Cell Cycle Progression ◽  
Nucleotide Exchange ◽  
Normal Cells ◽  
Cytoplasmic Transport ◽  
Dividing Cells ◽  
Ran Gtp

The coordination of cell cycle progression with the repair of DNA damage supports the genomic integrity of dividing cells. The function of many factors involved in DNA damage response (DDR) and the cell cycle depends on their Ran GTPase–regulated nuclear–cytoplasmic transport (NCT). The loading of Ran with GTP, which is mediated by RCC1, the guanine nucleotide exchange factor for Ran, is critical for NCT activity. However, the role of RCC1 or Ran⋅GTP in promoting cell proliferation or DDR is not clear. We show that RCC1 overexpression in normal cells increased cellular Ran⋅GTP levels and accelerated the cell cycle and DNA damage repair. As a result, normal cells overexpressing RCC1 evaded DNA damage–induced cell cycle arrest and senescence, mimicking colorectal carcinoma cells with high endogenous RCC1 levels. The RCC1-induced inhibition of senescence required Ran and exportin 1 and involved the activation of importin β–dependent nuclear import of 53BP1, a large NCT cargo. Our results indicate that changes in the activity of the Ran⋅GTP–regulated NCT modulate the rate of the cell cycle and the efficiency of DNA repair. Through the essential role of RCC1 in regulation of cellular Ran⋅GTP levels and NCT, RCC1 expression enables the proliferation of cells that sustain DNA damage.

Sign in / Sign up

Export Citation Format

Share Document