REDOX REGULATION OF NF-KAPPA-B DNA-BINDING ACTIVITY BY DIHYDROLIPOATE

NF-kappa B transcription factor regulates a wide variety of cellular a nd viral genes including the human immonodeficiency virus type 1. Here , we demonstrate that dihydrolipoate/alpha-lipoate redox couple which is a cofactor for mitochondrial dehydrogenases reactions, influences t he DNA binding activity of NF-kappa B. The elimination of dithiothreit ol in the electrophoretic mobility shift assay protocol resulted in th e inability to detect DNA binding activity of activated NF-kappa B. Th e DNA binding activity was restored by the addition of dihydrolipoate in the binding reaction mixture. Inhibition of NF-kappa B DNA binding activity by in vitro exposure to a sulfhydryl oxidizing agent, diamide was also blocked by dihydrolipoate. In contrast, the addition of the oxidized form, alpha-lipoate inhibited the NF-kappa B DNA binding acti vity. Coincidentally, preincubation of Jurkat cells with dihydrolipoat e potentiated and alpha-lipoate inhibited the okadaic acid-induced NF- kappa B activation as detected by assessing its DNA binding activity. These results suggest the redox exchange between lipoate and NF-kappa B molecules. Furthermore, since the inhibition of AP-1 DNA binding act ivity by diamide was also blocked by dihydrolipoate, this natural redu ctant may participate in the redox regulation of transcription factors by enhancing the DNA-protein interactions.