Calmodulin antagonists and cAMP inhibit ionizing-radiation-enhancement of double-strand-break repair in human cells.
Ionizing radiation (IR) enhances double-strand-break (DSB)-repair fidelity in plasmids processed in normal lymphoblasts but not in lymphoblasts from ataxia telangiectasia (A-T) patients. Putatively, signal-transduction pathways mediate this DNA-repair induction. Because IR inhibition of DNA synthesis is defective in A-T cells and is mediated by a calmodulin (caM)-dependent pathway, we evaluated the involvement of caM-dependent pathways in DSB-repair induction. Human lymphoblasts were gamma-irradiated with or without treatment with caM antagonists and the cells' abilities to repair shuttle pZ189 carrying a single DSB (linDNA) were assessed. In untreated controls, IR enhanced DSB-rejoining fidelity if transfection occurred promptly but diminished fidelity if transfection was delayed. Treatment with two caM antagonists, W-7 and W-13, prior to irradiation blocked this IR-enhancement of DSB-rejoining fidelity. Vinpocetine, a caM-dependent phosphodiesterase inhibitor, and 8-bromo-cAMP also inhibited IR enhancement of repair fidelity, but caM-dependent protein kinase II inhibitor KN62 had no effect. Other protein kinase inhibitors, staurosporine and genistein, also did not inhibit IR enhancement of DSB repair fidelity. However, staurosporine blocked the twofold reduction in DSB-repair fidelity seen if linDNA transfection was delayed 2 h after irradiation. These findings point to the involvement of caM/cAMP-dependent pathway(s) in mediating IR-enhancement of DSB-rejoining fidelity in mammalian cells.
Wang
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Division of Oral and Maxillofacial Radiology, Department of Oral Diagnosis, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT 06030-mc1605, USA.
Mallya
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Sikpi
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D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002147:Calmodulin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002460:Cell Line; D000242:Cyclic AMP / Q000494:pharmacology*; D004247:DNA / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005720:Gamma Rays; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D009154:Mutation / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D010957:Plasmids / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects*; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D014748:Vinca Alkaloids / Q000494:pharmacology
D002147:Calmodulin; D004791:Enzyme Inhibitors; D013449:Sulfonamides; D014748:Vinca Alkaloids; D015124:8-Bromo Cyclic Adenosine Monophosphate; C013983:vinpocetine; C017967:W 7; C033772:N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide; D004247:DNA; D019833:Genistein; D000242:Cyclic AMP; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D019311:Staurosporine