Hierarchy and positive/negative interplays of the hepatocyte nuclear factors HNF-1, -3 and -4 in the liver-specific enhancer for the human alpha-1-microglobulin/bikunin precursor.
Alpha-1-microglobulin and bikunin are two plasma glycoproteins encoded by an alpha-1-microglobulin/bikunin precursor (AMBP) gene. The strict liver-specific expression of the AMBP gene is controlled by a potent enhancer made of six clustered boxes numbered 1-6 that have been reported to be proven or potential binding sites for the hepatocyte-enriched nuclear factors HNF-1, -4, -3, -1, -3, -4, respectively. In the present study, electromobility shift assays of wild-type or mutated probes demonstrated that the boxes 1-5 have a binding capacity for their cognate HNF protein. Box 5 is also a target for another, as yet unidentified, factor. A functional analysis of the wild-type or mutated enhancer, driving its homologous promoter and a reporter CAT gene in the HepG2 hepatoma cell line, demonstrated that all six boxes participate in the enhancer activity, with the primary influence of box 4 (HNF-1) and box 2 (HNF-4). A similar analysis in the HNF-free CHO cell line co-transfected with one or several HNF factors further demonstrated various interplays between boxes: box 3 (HNF-3 alpha and beta) has a negative influence over the major HNF-4 box 2 as well as a positive influence over the major HNF-1 box 4.
Rouet
P
P
INSERM Unit 78, Boisguillaume, France.
Raguenez
G
G
Tronche
F
F
Mfou'ou
V
V
Salier
J P
JP
D000510:Alpha-Globulins / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D016466:CHO Cells; D006224:Cricetinae; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D006023:Glycoproteins / Q000235:genetics*; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D051557:Hepatocyte Nuclear Factor 4; D006801:Humans; D008099:Liver / Q000166:cytology / Q000378:metabolism; D008562:Membrane Glycoproteins; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D011498:Protein Precursors / Q000235:genetics; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics*; D014162:Transfection; D014360:Trypsin Inhibitor, Kunitz Soybean; D014407:Tumor Cells, Cultured
D000510:Alpha-Globulins; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D006023:Glycoproteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D051557:Hepatocyte Nuclear Factor 4; C403128:MLX protein, human; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011498:Protein Precursors; C109148:SPINT2 protein, human; D014157:Transcription Factors; C016001:alpha-1-microglobulin; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta; D004247:DNA; D014360:Trypsin Inhibitor, Kunitz Soybean