Association of hepatic nuclear factor-4 in the apolipoprotein B promoter: a preliminary report

Author(s)

E.M. Nóvak ^[1] ; K.C. Dantas ^[2] ; C.E. Charbel ^[3] ; S.P. Bydlowski

Affiliation

^[1] Fundação Pró-Sangue Hemocentro de São Paulo

^[2] Fundação Pró-Sangue Hemocentro de São Paulo

^[3] Fundação Pró-Sangue Hemocentro de São Paulo

• Document type: Journal article
• Source: Brazilian Journal of Medical and Biological Research; v. 31, n. 11, p. 1405-1408, 1998-11-00.

Abstract

Previous studies have examined the arrangement of regulatory elements along the apolipoprotein B (apoB) promoter region (-3067 to +940) and a promoter fragment extending from nucleotides -150 to +124 has been demonstrated to be essential for transcriptional activation of the apoB gene in hepatic and intestinal cells. It has also been shown that transcriptional activation of apoB requires a synergistic interaction between hepatic nuclear factor-4 (HNF-4) and CCAAT/enhancer-binding protein a (C/EBPa) transcription factors. Here, we have examined the hypothesis that HNF-4 factor binding to DNA may induce a DNA helix bend, thus facilitating the communication with a C/EBPa factor located one helix turn from this HNF-4 factor in the apoB promoter. A gel electrophoretic mobility shift assay using wild type double-stranded oligonucleotides or modified wild type duplex oligonucleotides with 10 nucleotides inserted between HNF-4 and C/EBPa factor motifs showed similar retarded complexes, indicating that HNF-4 and C/EBPa factors interact independently of the distance between binding sites. However, when only one base, a thymidine, was inserted at the -71 position of the apoB promoter, the complex shift was completely abolished. In conclusion, these results regarding the study of the mechanisms involving the interaction between HNF-4 and C/EBPa factors in the apoB promoter suggest that the perfect 5'-CCCTTTGGA-3' motif is needed in order to facilitate the interaction between the two factors. (AU)