C/EBP-β is a LPS-induced Nuclear Factor that Binds to the C/EBP Element of the SerpinB2 Proximal Promoter
The C/EBP family of basic leucine zipper transcription factors are known for their roles in cellular differentiation and inflammation [59]. Consisting of six members, the C/EBP transcription factors can homo−/heterodimerize and display similar DNA binding specificities [60]. Four family members, C/EBP-α, C/EBP-β, C/EBP-δ and C/EBP-ε, are present in myeloid cells and play different roles in differentiating myeloid cells depending on the extracellular environment [61]. To determine which C/EBP proteins were involved in the formation of the different nucleo-protein complexes, and particularly of the LPS-inducible complex, EMSA was performed after incubating the nucleo-protein complexes with antibodies specific for C/EBP-α, C/EBP-β, C/EBP-δ and C/EBP-ε. Each antibody detects the carboxy-terminal DNA-binding region of the respective protein, so that pre-incubation of antibody with nuclear extract is expected to abolish DNA binding by EMSA [62]. Only antibodies against C/EBP-β abolished the formation of the LPS-inducible complex (Fig. 5C). Taken together these data show that the LPS-induced complex with the C/EBP element (−203/−192) contains C/EBP-β.