The bifunctional protein DCoH modulates interactions of the homeodomain transcription factor HNF1 with nucleic acids

J Mol Biol. 1997 Jan 10;265(1):20-9. doi: 10.1006/jmbi.1996.0708.


The hepatocyte nuclear factor-1 (HNF1) is a homeodomain transcription factor that binds DNA as a dimer. HNF1 dimers associate with two molecules of DCoH, a bifunctional protein that also has an enzymatic function in the tetrahydrobiopterin regeneration, to form stable heterotetramers also capable of DNA binding. Employing purified, recombinant HNF1, HNF1/DCoH heterotetramers and DCoH homotetramers we investigated whether DCoH affects interactions of HNF1 with nucleic acids. Although we detected no direct binding of DCoH to DNA or RNA, DCoH stabilized HNF1/DNA complexes and promoted interactions with sub-optimal DNA target sequences such as the human alpha1-antitrypsin TATA box region. Importantly, we also observed interactions of HNF1 with RNA, but these interactions were completely abolished when HNF1 was complexed with DCoH. Interestingly, DCoH retains its enzymatic activity while complexed with HNF1. Our results document intermolecular regulation of HNF1 binding to nucleic acids by DCoH.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • DNA / metabolism
  • DNA Probes / genetics
  • DNA-Binding Proteins*
  • Dimerization
  • Escherichia coli / genetics
  • Hepatocyte Nuclear Factor 1
  • Hepatocyte Nuclear Factor 1-alpha
  • Hepatocyte Nuclear Factor 1-beta
  • Humans
  • Hydro-Lyases / chemistry
  • Hydro-Lyases / genetics
  • Hydro-Lyases / metabolism*
  • Nuclear Proteins*
  • Nucleic Acids / metabolism*
  • Protein Binding
  • Protein Conformation
  • RNA / metabolism
  • Rats
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Transcription Factors / chemistry
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*


  • DNA Probes
  • DNA-Binding Proteins
  • HNF1A protein, human
  • HNF1B protein, human
  • Hepatocyte Nuclear Factor 1-alpha
  • Hnf1a protein, rat
  • Nuclear Proteins
  • Nucleic Acids
  • Recombinant Proteins
  • Transcription Factors
  • Hepatocyte Nuclear Factor 1
  • Hepatocyte Nuclear Factor 1-beta
  • RNA
  • DNA
  • Hydro-Lyases
  • pterin-4a-carbinolamine dehydratase