NF-kappa B is involved in the induction of the rat hepatic alpha 1-acid glycoprotein gene by phenobarbital

Phenobarbital, a classical inducer of the drug-metabolizing cytochrome P450 genes, induces alpha 1-acid glycoprotein gene expression through a PB-resp onsive element (PBRE) located at position -142 to -126 from the transcripti onal start site. The aim of this study was to investigate nuclear protein b inding to the PBRE sequence after PB treatment. Cycloheximide treatment sho wed that de novo protein synthesis was not required for PB to induce AGP ge ne expression, pointing to post-translational modifications. Studies of the DNA-protein complex with the PBRE showed that phosphorylation status is a key regulator of the binding capacity of transactivating proteins involved in PB transcriptional activation. This DNA-protein complex, analyzed by sou thwestern blotting and UV cross-linking, involves three nuclear factors wit h molecular weights of 43, 52, and 65 kDa. Supershift and competition exper iments showed that the 43-kDa factor can be related to C/EBP alpha and the 52- and 65-kDa factors to the two subunits of NF-kappa B. (C) 1999 Academic Press.