CCAAT box enhancer binding protein alpha (C/EBP- alpha ) stimulates Kappa B element-mediated transcription in transfected cells

• Published in: The Journal of biological chemistry Vol. 271; no. 10; pp. 5595 - 5602
• Main Authors: Vietor, I, Oliveira, I C, Vilcek, J
• Format: Journal Article
• Language: English
• Published: 08.03.1996
• ISSN: 0021-9258
• DOI: 10.1074/jbc.271.10.5595

A construct comprising three tandemly repeated copies of the Kappa B element from the interleukin-8 gene linked to chloramphenicol acetyltransferase (CAT) (3xNF- Kappa BCAT) was transcriptionally activated in normal human FS-4 fibroblasts by co-transfection with expression vectors for NF- Kappa B p50, p65, or p52. Unexpectedly, a significant activation of 3xNF- Kappa BCAT was also seen upon its co-transfection with the expression vector for CCAAT box enhancer binding protein alpha (C/EBP- alpha ) (but not C/EBP- beta or C/EBP- delta ). Stimulation by C/EBP- alpha required some other factor(s) present in FS-4 cells because no transcriptional activation of 3xNF- Kappa BCAT was seen after co-transfection with C/EBP- alpha in F9 mouse embryonic carcinoma cells, known to be deficient in several transcription factors. To determine whether transcriptional activation was the result of interaction with one of the major NF- Kappa B proteins, we co-transfected C/EBP- alpha with NF- Kappa B p50, p65, p50 + p65, or p52 into F9 or FS-4 cells. No cooperative interaction was seen; in fact, C/EBP- alpha reduced p65-stimulated transcription, especially in F9 cells. Electrophoretic mobility shift assay with a Kappa B probe revealed that the addition of recombinant C/EBP- alpha protein to nuclear extracts from untreated FS-4 cells resulted in the appearance of four bands. Only one of these bands was supershifted by antibody to p50, whereas antibodies to p65 or other NF- Kappa B proteins had no effect. Our findings show that C/EBP- alpha may cause activation of some Kappa B element-containing genes lacking C/EBP binding sites.