Modulation of the DNA binding activity of transcription factors CREP, NFκB and HSF by H2O2 and TNFα. Differences between in vivo and in vitro effects

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Abstract
Human endothelial cells exposed to H2O2 showed reduced CREP DNA binding activity, enhanced HSF activation, and no induction of NFκB binding activity. Interestingly, H2O2 was able to induce NFκB subunit p65 translocation in the nucleus. In contrast, cells exposed to TNFα showed enhanced CREP binding activity, activation of NFκB and no induction of HSE‐HSF complex. Addition of H2O2, diamide and iodoacetic acid to the binding reaction mixture markedly reduced the DNA binding ability of the three transcription factors. Thus free sulfhydryls were important in DNA binding activity of CREP, NFκB and HSF, and the lack of induction of NFκB by H2O2 in intact cells was likely caused by oxidation on a thiol, and not by a deficiency in the activation pathway.