Characterization of DNA polymerase β mRNA: cell-cycle and growth response in cultured human cells

AbstractTargeting PARP1 [Poly(ADP-Ribose) Polymerase 1] for synthetic lethality is a new strategy for BRCA germ-line mutated or platinum sensitive ovarian cancers. However, not all patients respond due to intrinsic or acquired resistance to PARP1 inhibitor. Development of alternative synthetic lethality approaches is a high priority. DNA polymerase β (Polβ), a critical player in base excision repair (BER), interacts with PARP1 during DNA repair. Here we show that polβ deficiency is a predictor of platinum sensitivity in human ovarian tumours. Polβ depletion not only increased platinum sensitivity but also reduced invasion, migration and impaired EMT (epithelial to mesenchymal transition) of ovarian cancer cells. Polβ small molecular inhibitors (Pamoic acid and NSC666719) were selectively toxic to BRCA2 deficient cells and associated with double-strand breaks (DSB) accumulation, cell cycle arrest and increased apoptosis. Interestingly, PARG [Poly(ADP-Ribose) Glycohydrolase] inhibitor (PDD00017273) [but not PARP1 inhibitor (Olaparib)] was synthetically lethal in polβ deficient cells. Selective toxicity to PDD00017273 was associated with poly (ADP-ribose) accumulation, reduced nicotinamide adenine dinucleotide (NAD+) level, DSB accumulation, cell cycle arrest and increased apoptosis. In human tumours, polβ-PARG co-expression adversely impacted survival in patients. Our data provide evidence that polβ targeting is a novel strategy and warrants further pharmaceutical development in epithelial ovarian cancers.

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Cytotoxic, genotoxic and cell-cycle disruptive effects of thio-dimethylarsinate in cultured human cells and the role of glutathione

Toxicology and Applied Pharmacology ◽

10.1016/j.taap.2007.11.023 ◽

2008 ◽

Vol 228 (1) ◽

pp. 59-67 ◽

Cited By ~ 61

Author(s):

Takafumi Ochi ◽

Kayoko Kita ◽

Toshihide Suzuki ◽

Alice Rumpler ◽

Walter Goessler ◽

...

Keyword(s):

Cell Cycle ◽

Human Cells ◽

Cultured Human Cells

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Detection and characterization of DNA polymerase activity in Toxoplasma gondii

Parasitology ◽

10.1017/s0031182000067238 ◽

1993 ◽

Vol 107 (2) ◽

pp. 135-139 ◽

Cited By ~ 10

Author(s):

A. Makioka ◽

B. Stavros ◽

J. T. Ellis ◽

A. M. Johnson

Keyword(s):

Toxoplasma Gondii ◽

Dna Polymerase ◽

Dna Polymerases ◽

Sedimentation Coefficient ◽

Polymerase Activity ◽

Magnesium Ions ◽

Dna Polymerase Β ◽

Human Dna ◽

Approximate Molecular Weight

SUMMARYA DNA polymerase activity has been detected and characterized in crude extracts from tachzoites of Toxoplasma gondii. The enzyme has a sedimentation coefficient of 6·4 S, corresponding to an approximate molecular weight of 150000 assuming a globular shape. Like mammalian DNA polymerase α, the DNA polymerase of T. gondii was sensitive to N-ethylmaleimide and inhibited by high ionic strength. However, the enzyme activity was not inhibited by aphidicolin which is an inhibitor of mammalian DNA polymerases α, δ and ε and also cytosine-β-D-arabinofuranoside-5′-triphosphate which is an inhibitor of α polymerase. The activity was inhibited by 2′,3′-dideoxythymidine-5′-triphosphate which is an inhibitor of mammalian DNA polymerase β and γ. Magnesium ions (Mg2+) were absolutely required for activity and its optimal concentration was 6 mM. The optimum potassium (K+) concentration was 50 mM and a higher concentration of K+ markedly inhibited the activity. Activity was optimal at pH 8. Monoclonal antibodies against human DNA polymerase did not bind to DNA polymerase of T. gondii. Thus the T. gondii enzyme differs from the human enzymes and may be a useful target for the design of toxoplasmacidal drugs.

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