Analysis of hepatocyte nuclear factor-3 beta protein domains required for transcriptional activation and nuclear targeting.
Three distinct hepatocyte nuclear factor 3 (HNF-3) proteins (alpha, beta and gamma) regulate transcription of the transthyretin (TTR) and numerous other liver-specific genes. The HNF-3 proteins bind DNA via a homologous winged helix motif common to a number of developmental regulatory proteins including the Drosophila homeotic fork head (fkh) protein. The mammalian HNF-3/fkh family consists of at least thirty distinct members and is expressed in a variety of different cellular lineages. In addition to the winged helix motif, several HNF-3/fkh family members also share homology within transcriptional activation region II and III sequences. In the present study we further define the sequence boundaries of the HNF-3 beta N-terminal transcriptional activation domain to extend from amino acids 14 to 93 and include conserved region IV and V sequences. We also demonstrate that activity of the HNF-3 N-terminal domain was diminished by mutations which altered a putative alpha-helical structure located between amino acid residues 14 and 19. However, transcriptional activity was not affected by mutations which eliminated two conserved casein kinase I sites or increased the number of acidic amino acid residues in the N-terminal domain. Furthermore, we determined that the nuclear localization signal overlaps with the winged helix DNA-binding motif. These results suggest that conserved sequences within the winged helix motif of the HNF-3/fkh family may be involved not only in DNA recognition, but also in nuclear targeting.
Qian
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Department of Biochemistry, College of Medicine, University of Illinois at Chicago 60612-7334, USA.
Costa
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D047388:Casein Kinases; D002467:Cell Nucleus / Q000378:metabolism; D017124:Conserved Sequence; D004247:DNA / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D051542:Hepatocyte Nuclear Factor 3-beta; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010766:Phosphorylation; D011392:Proline / Q000235:genetics; D011494:Protein Kinases; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors; D015533:Transcriptional Activation; D001616:beta-Galactosidase / Q000378:metabolism
D017931:DNA Primers; D004268:DNA-Binding Proteins; C496502:FOXA2 protein, human; D009687:Nuclear Proteins; D014157:Transcription Factors; D051542:Hepatocyte Nuclear Factor 3-beta; D004247:DNA; D011392:Proline; D011494:Protein Kinases; D047388:Casein Kinases; D001616:beta-Galactosidase