The class III POU factor Brn-4 interacts with other class III POU factors and the heterogeneous nuclear ribonucleoprotein U

Brain Res Mol Brain Res. 1997 Apr;45(1):99-107. doi: 10.1016/s0169-328x(96)00238-0.

Abstract

The class III POU proteins are expressed throughout the central nervous system, including the hypothalamus, where they are often co-localized. Presumably, these POU proteins (Brain-1, Brain-2, Brain-4 and SCIP) serve as transcriptional transactivators. That they are co-expressed in some neurons suggests that, if they were to form homomeric and heteromeric complexes with each other, depending on the particular combination, they might have different DNA-binding specificities and, thus, activate different genes. We used purified fusion proteins of the four class III POU proteins in far-western assays to show that the proteins can interact. We confirmed their interactions using a two-hybrid system. Both techniques indicate that the interaction occurs through the POU domain. The far-western technique also allowed us to identify a 120-kDa nuclear protein that interacts with Brain-4. Subsequent affinity purification and microsequencing identified the protein as the heterogeneous nuclear ribonucleoprotein U (hnRNP U). This result suggests another mechanism by which a POU protein can influence gene expression: by facilitating the processing of pre-mRNA whose transcription it has stimulated.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Blotting, Western
  • Cell Nucleus / metabolism
  • DNA-Binding Proteins*
  • Gene Expression
  • Glutathione Transferase
  • Heterogeneous-Nuclear Ribonucleoprotein U
  • Heterogeneous-Nuclear Ribonucleoproteins
  • Hypothalamus / metabolism
  • Molecular Sequence Data
  • Nerve Tissue Proteins*
  • Nervous System / metabolism*
  • Oligopeptides
  • POU Domain Factors
  • Peptide Fragments / chemistry
  • Peptides
  • Polymerase Chain Reaction
  • Protein Binding
  • Protein Multimerization
  • RNA Precursors / metabolism
  • Rats
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / isolation & purification
  • Recombinant Fusion Proteins / metabolism
  • Ribonucleoproteins / chemistry
  • Ribonucleoproteins / isolation & purification
  • Ribonucleoproteins / metabolism*
  • Transcription Factors / chemistry
  • Transcription Factors / isolation & purification
  • Transcription Factors / metabolism*
  • Transcription, Genetic
  • Two-Hybrid System Techniques

Substances

  • DNA-Binding Proteins
  • Heterogeneous-Nuclear Ribonucleoprotein U
  • Heterogeneous-Nuclear Ribonucleoproteins
  • Nerve Tissue Proteins
  • Oligopeptides
  • POU Domain Factors
  • Peptide Fragments
  • Peptides
  • Pou3f4 protein, rat
  • RNA Precursors
  • Recombinant Fusion Proteins
  • Ribonucleoproteins
  • Transcription Factors
  • FLAG peptide
  • Glutathione Transferase