potassium-bromate and Ataxia-Telangiectasia

The ataxia telangiectasia mutated (ATM) protein is a pivotal multifunctional protein kinase predominantly involved in DNA damage response, as well as in maintaining overall functional integrity of the cells. Apart from playing its major role in regulating the cellular response to DNA damage, ATM, when mutated, can additionally determine oxidative stress, metabolic syndrome, mitochondrial dysfunction and neurodegeneration. In the present paper we aim to investigate the levels of oxidative stress potentially induced by the oxidizing rodent renal carcinogen KBrO

Topics: Ataxia Telangiectasia; Ataxia Telangiectasia Mutated Proteins; Bromates; Cells, Cultured; DNA Damage; DNA Repair; Humans; Hypersensitivity; Lymphocytes; Oxidative Stress; Phosphorylation; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors

Fanconi anemia (FA) and ataxia telangiectasia (AT) share common traits such chromosomal instability and proneness to hematological cancers. Both AT and FA cell lines, and patients, are characterized by abnormally high levels of oxidative stress markers. The key FA protein FANCD2 is phosphorylated on Ser 222 by ATM after ionizing radiation (IR), thus allowing normal activation of the S-phase checkpoint, and ATM cells are known to be hypersensitive to oxidative damage. In this work we show that FANCD2 deficient cells have a defective S-phase checkpoint after Hydrogen Peroxide (H(2)O(2)) induced oxidative damage. ATM dependent phosphorylation of FANCD2 at the S222 residue is necessary for normal S-phase checkpoint activation after oxidative stress, while FANCD2 monoubiquitination at K561 is dispensable. We also show that FANCD2 is not required for base excision repair of 8-oxoG and other DNA lesions (abasic sites, uracils), while treatments that exclusively induce 8-oxoG, but not DNA double strand breaks, fail to activate FANCD2 monoubiquitination, thus indicating that the known accumulation of 8-oxoG in FA cells reflects an overproduction of ROS rather than defective processing of oxidized bases. We conclude that the handling of DNA damage after H(2)O(2)-induced oxidative stress requires the coordinated action of FANCD2 and ATM.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Ataxia Telangiectasia; Ataxia Telangiectasia Mutated Proteins; Bromates; Cell Cycle Proteins; Cell Line; Deoxyguanosine; DNA; DNA Damage; DNA Repair; DNA-Binding Proteins; Fanconi Anemia; Fanconi Anemia Complementation Group D2 Protein; Histones; Humans; Hydrogen Peroxide; Mice; Oxidants; Phosphorylation; Protein Serine-Threonine Kinases; S Phase; Tumor Suppressor Proteins; Ubiquitination