Search results for "Poly A"

Corrigendum to "poly (ADP-ribose) polymerase inhibition synergizes with the NF-κB inhibitor DHMEQ to kill hepatocellular carcinoma cells" [Biochim. B…

2018

Fig. 1. The effects of the DHMEQ–Olaparib combination on HCC cells. (A) Cells were treated for 72 hwith the indicated concentrations of DHMEQ–Olaparib and cell viability was assessed by MTS assays. The DHMEQ–Olaparib combination showed synergistic inhibition of cell viability in Hep3B cells and additive inhibition in Huh7 cells. Combination index (CI) values are indicated above the bar. Data are expressed as percent cell growth and are the mean ± SD of three separate experiments (each of which was performed in triplicate). *p b 0.05 and **p b 0.01 versus each agent alone. (B) Cells were treated for 24 h with DHMEQ (μg/ml) or Olaparib (μM) alone or in combination, allowed to grow for 14 days…

KRAS-mutated iCCA display distinct molecular alterations and a preferential sensitivity towards PARP-1 inhibition

2021

Miltirone Induces G2/M Cell Cycle Arrest and Apoptosis in CCRF-CEM Acute Lymphoblastic Leukemia Cells

2015

Miltirone (1) is a diterpene quinone extracted from a well-known Chinese traditional herb (Salvia miltiorrhiza). We investigated the cytotoxic effects of miltirone toward sensitive and multidrug-resistant acute lymphoblastic leukemia cell lines. Miltirone inhibited multidrug-resistant P-glycoprotein (P-gp)-overexpressing CEM/ADR5000 cells better than drug-sensitive CCRF-CEM wild-type cells, a phenomenon termed collateral sensitivity. Flow cytometric analyses revealed that miltirone induced G2/M arrest and apoptosis. Furthermore, miltirone stimulated reactive oxygen species (ROS) generation and mitochondrial membrane potential (MMP) disruption, which in turn induced DNA damage and activation…

Poly (ADP-ribose) polymerase inhibition synergizes with the NF-κB inhibitor DHMEQ to kill hepatocellular carcinoma cells

2014

Poly (ADP-ribose) polymerase (PARP) enzymes play a key role in the cellular machinery responsible for DNA repair. Dehydroxymethylepoxyquinomicin (DHMEQ), a new inhibitor of NF-κB, induces oxidative stress and DNA damage. The effects of DHMEQ in combination with Olaparib (PARP inhibitor) were studied on hepatocellular carcinoma (HCC) cells. The DHMEQ-Olaparib combination synergistically inhibited cell viability, cell proliferation and colony formation of Hep3B, but had additive effects on Huh7 cells. The synergistic effects of the combination correlated with increased apoptosis, caspase 3/7 activity and PARP cleavage. There was an induction of an endoplasmic reticulum (ER) stress response wi…

Poly(ADP-ribosyl)ation accelerates DNA repair in a pathway dependent on Cockayne syndrome B protein

2003

Activation of poly(ADP-ribose)polymerases 1 and 2 (PARP-1 and PARP-2) is one of the earliest responses of mammalian cells to DNA damage by numerous genotoxic agents. We have analysed the influence of PARP inhibition, either achieved by over-expression of the DNA binding domain of PARP-1 or by treatment with 3,4-dihydro-5-[4-(1-piperidinyl)butoxyl]-1(2H)-isoquinolinone, on the repair of single-strand breaks (SSB), pyrimidine dimers and oxidative base modifications sensitive to Fpg protein (mostly 8-hydroxyguanine) in mammalian cells at very low, non-cytotoxic levels of DNA damage. The data show that the repair rates of all three types of DNA damage are significantly lower in PARP-inhibited c…

Parvovirus B19 nonstructural protein-induced damage of cellular DNA and resultant apoptosis.

2010

Parvovirus B19 is a widespread virus with diverse clinical presentations. The viral nonstructural protein, NS1, binds to and cleaves the viral genome, and induces apoptosis when transfected into nonpermissive cells, such as hepatocytes. We hypothesized that the cytotoxicity of NS1 in such cells results from chromosomal DNA damage caused by the DNA-nicking and DNA-attaching activities of NS1. Upon testing this hypothesis, we found that NS1 covalently binds to cellular DNA and is modified by PARP, an enzyme involved in repairing single-stranded DNA nicks. We furthermore discovered that the DNA nick repair pathway initiated by poly(ADPribose)polymerase and the DNA repair pathways initiated by …

Late activation of stress kinases (SAPK/JNK) by genotoxins requires the DNA repair proteins DNA-PKcs and CSB.

2005

Although genotoxic agents are powerful inducers of stress kinases (SAPK/JNK), the contribution of DNA damage itself to this response is unknown. Therefore, SAPK/JNK activation of cells harboring specific defects in DNA damage-recognition mechanisms was studied. Dual phosphorylation of SAPK/JNK by the genotoxin methyl methanesulfonate (MMS) occurred in two waves. The early response (≤2 h after exposure) was similar in cells knockout for ATM, PARP, p53, and CSB or defective in DNA-PKcscompared with wild-type cells. The late response however (≥4 h), was drastically reduced in DNA-PKcsand Cockayne's syndrome B (CSB)-deficient cells. Similar results were obtained with human cells lacking DNA-PKc…

More firms, more competition? The case of the fourth operator in France's mobile phone market

2010

Accepted, Forthcoming; International audience; To foster competition the French government authorized a fourth operator, ‘Free', to enter the country's mobile phone market at the end of 2009 alongside Orange, SFR and Bouygues Telecom (BT), who held respectively one-half, one-third and one-sixth of the market. By using a stylized model of France's phone market, we have examined what we call the regulator's nightmares and dreams. If Cournot competition is in place before Free's entry, minimizing the total profit fails to maximize the consumer surplus and the total surplus; the maximum most realistic price fall is 6.7% compared to three-way competition and could be 1.7% only; if Orange, SFR an…

Endoribonuclease IV. A poly(A)-specific ribonuclease from chick oviduct. 1. Purification of the enzyme.

1976

A new endoribonuclease, termed endoribonuclease IV, has been described. This enzyme has been isolated from chick oviducts and purified 15 000-fold in a 25% yield nearly to homogeneity. The nuclease, which specifically degrades poly(A), forms oligonucleotides of an average chain length of 10. These (A)-10 fragments are terminated by 3'-hydroxyl and 5'-phosphate groups. The enzyme has a pH optimum at 8.7, requires Mn2+ or Mg2+ as a cofactor, and has a molecular weight of about 45 000.

Control of Enzymic Hydrolysis of Polyadenylate Segment of Messenger RNA: Role of Polyadenylate-Associated Proteins

1978

The role of poly(A)-associated proteins in the breakdown of poly(A) sequences in both mammalian polyribosomes and in isolated poly(A) · protein complexes has been studied on an enzymic level. Two nucleases (alkaline exoribonuclease and endoribonuclease IV; both isolated from eukaryotic tissue), which preferentially hydrolyze poly(A) sequences, have been applied to determine the susceptibility of poly(A) in dependence on the presence of poly(A) · protein(s). Polysomes, isolated from L5178y mouse lymphoma cells, do not contain endogenous poly(A) nuclease activity. The poly(A) segment in polysomes is hydrolyzed by the exoribonuclease, irrespective of the preincubation conditions used. Pretreat…