Nitric oxide inhibits c-Jun DNA binding by specifically targeted S-glutathionylation

This study addresses potential molecular mechanisms underlying the inhibiti on of the transcription factor c-Jun by nitric oxide. We show that in the p resence of the physiological sulfhydryl glutathione nitric oxide modifies t he two cysteine residues contained in the DNA binding module of c-Jun in a selective and distinct way. Although nitric oxide induced the formation of an intermolecular disulfide bridge between cysteine residues in the leucine zipper site of c-Jun monomers, this same radical directed the covalent inc orporation of stoichiometric amounts of glutathione to a single conserved c ysteine residue in the DNA-binding site of the protein. We found that coval ent dimerization of c-Jun apparently did not affect its DNA binding activit y, whereas the formation of a mixed disulfide with glutathione correlated w ell with the inhibition of transcription factor binding to DNA. Furthermore , we provide experimental evidence that nitric oxide-induced S-glutathionyl ation and inhibition of c-Jun involves the formation of S-nitrosoglutathion e. In conclusion, our results support the reversible formation of a mixed d isulfide between glutathione and c-Jun as a potential mechanism by which ni trosative stress may be transduced into a functional response at the level of transcription.