The activity of the activation function 2 of the human hepatocyte nuclear factor 4 (HNF-4alpha) is differently modulated by F domains from various origins.
Hepatocyte nuclear factor 4 (HNF-4) is a member of the nuclear hormone-receptor superfamily, which plays an important role in the regulation of several genes involved in numerous metabolic pathways. HNF-4 contains a DNA-binding domain located in domain C and two activation-function domains, designated AF-1 and AF-2, located in domains A/B and E, respectively. The seven isoforms of human HNF-4, termed alpha1-alpha6 and gamma, differ mainly by their A/B and F domains. The high sequence variability of the F domain led us to investigate whether this domain modulates the transcriptional activity of HNF-4. Using constructs having the same core receptor and different F domains, we observed that the F domains of HNF-4 modulate the transactivating activity of the full-length HNF-4. A more precise analysis using HNF-4alpha AF-2 fused to GAL4 protein and various F domains demonstrated that F domains of isoforms alpha3 and gamma exhibited inhibitory effects on the activation function AF-2 but that their inhibition behaviours were weaker than that of HNF-4alpha2 F domain, which has been reported previously. The presence of domain F results in a decreased interaction with the co-activator glucocorticoid receptor-interacting protein 1. For a given F domain, the modulating effects on the full-length HNF-4 as well as on the AF-2 depended on the target promoters. Our results suggest that the presence of domain F results in conformation changes in HNF-4 AF-2 or in its spatial environment, which probably modify the interaction of the AF-2 activation domain with co-factors and transcription factors bound to cis-elements of the target promoters.
Suaud
L
L
Unité 459 INSERM, Laboratoire de Biologie Cellulaire, Faculté de Médecine H. Warembourg, 1 Place de Verdun, F 59045 Lille, France.
Formstecher
P
P
Laine
B
B
D000595:Amino Acid Sequence; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D001665:Binding Sites; D002460:Cell Line; D004268:DNA-Binding Proteins; D017930:Genes, Reporter; D051557:Hepatocyte Nuclear Factor 4; D006801:Humans; D008969:Molecular Sequence Data; D051958:Nuclear Receptor Coactivator 2; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C496592:HNF4A protein, human; D051557:Hepatocyte Nuclear Factor 4; C403128:MLX protein, human; D051958:Nuclear Receptor Coactivator 2; D010750:Phosphoproteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors