The cellular control enzyme polyADP ribosyl transferase is eliminated in cultured Fanconi anemia fibroblasts at confluency

Constitutive activation of caspase-3 and Poly ADP ribose polymerase cleavage in fanconi anemia cells

Fanconi anemia (FA) is a rare syndrome characterized by developmental abnormalities, progressive bone marrow failure, and cancer predisposition. Cells from FA patients exhibit hypersensitivity to DNA cross-linking agents and oxidative stress that may trigger apoptosis. Damage-induced activation of caspases and poly ADP ribose polymerase (PARP) enzymes have been described for some of the FA complementation groups. Here, we show the constitutive activation of caspase-3 and PARP cleavage in the FA cells without exposure to exogenous DNA-damaging factors. These effects can be reversed in the presence of reactive oxygen species scavenger N-acetylcystein. We also show the accumulation of oxidized proteins in FA cells, which is accompanied by the tumor necrosis factor (TNF)-alpha oversecretion and the upregulation of early stress response kinases pERK1/2 and p-P38. Suppression of TNF-alpha secretion by the extracellular signal-regulated kinase inhibitor PD98059 results in reduction of caspase-3 cleavage, suggesting a possible mechanism of caspases-3 activation in FA cells. Thus, the current study is the first evidence demonstrating the damage-independent activation of caspase-3 and PARP in FA cells, which seems to occur through mitogen-activated protein kinase activation and TNF-alpha oversecretion.

Impaired synthesis of heme oxygenase-1 in Fanconi anemia cells can be rescued by transfection of Fanconi wild-type cDNA

Fanconi anemia is a fatal, hereditary chromosome instability syndrome of early childhood with progressive pancytopenia and cancer-proneness. Hypersensitivity to alkylating agents points to DNA repair inefficiency. Excess reactive oxygen intermediates and hypersensitivity to oxygen, all features of Fanconi anemia cells, give evidence for a disturbed oxidative metabolism. Here, we report that expression of the inducible heme oxygenase-1, an essential antioxidative defense protein, is impaired in Fanconi anemia cells and can be reinstated with the transfection of Fanconi A wild-type cDNA. A causative interaction of Fanconi anemia proteins with transcription of selected proteins is indicated. The results enlighten the oxygen sensitivity in Fanconi anemia.