These results suggest that the GR plays an important role in GCmediated repression of CBG and is supported by a previous study showing that mice without a functional GR were resistant to DEXmediated repression of hepatic CBG mRNA. Despite the fact that the proximal promoters of the CBG gene have been cloned and that five putative transcription factorbinding sites within the sequence have been identified, the current study is the first to investigate the cisacting elements involved in GC regulation. Initial experiments delineating the DEX-responsiveness of the Cbg promoter established that the region encompassing 2145 bp from the transcription start site, which contains P1 and P2, was unresponsive to DEX treatment. The cis-regulatory elements associated with P1 and P2 have previously been identified as HNF1b and CP2, respectively, and, although the current study established that these cis-regulatory elements are not important for DEX mediated repression of CBG, the region was previously shown to be transcriptionally active and is probably required for minimal promoter activity.As the region 2295 bp from the transcription start site, which encompasses P1�CP5, resulted in DEX-induced repression of the Cbg promoter and recruited GR, this left the binding sites P3�CP5, as possible candidates for DEX-mediated repression of CBG expression. P3�CP5 have been suggested to resemble recognition sequences for DBP, HNF3a and C/EBPb, respectively, although this has not yet been unequivocally demonstrated experimentally. Site-directed mutagenesis of C/ EBPb, HNF3a, and DBP binding sites in the Cbg promoter narrowed down the candidate cis-acting elements and identified the C/EBPb cisregulatory site, but not HNF3a or DBP, as important in DEXinduced repression of CBG. In addition, a decrease in C/EBPb protein expression by siRNA resulted in the attenuation of DEX-induced repression of CBG mRNA and protein expression in BWTG3 cells, as well as GR recruitment to the Cbg promoter. In GW2580 further support of C/EBPb��s involvement in GC-mediated repression of CBG, we also show that the GR UNC1215 together with C/EBPb co-exist in a complex that occupies the C/EBPb cisregulatory position.