title: The class III POU factor Brn-4 interacts with other class III POU factors and the heterogeneous nuclear ribonucleoprotein U.
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.
authors.affiliation: Laboratory of Cell Biology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: K F
authors.initials: KF
authors.lastname: Malik
authors.forename: H
authors.initials: H
authors.lastname: Jaffe
authors.forename: J
authors.initials: J
authors.lastname: Brady
authors.forename: W S
authors.initials: WS
authors.lastname: Young
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins; D015870:Gene Expression; D005982:Glutathione Transferase; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D007031:Hypothalamus / Q000378:metabolism; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins; D009420:Nervous System / Q000378:metabolism*; D009842:Oligopeptides; D050809:POU Domain Factors; D010446:Peptide Fragments / Q000737:chemistry; D010455:Peptides; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D055503:Protein Multimerization; D012322:RNA Precursors / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012261:Ribonucleoproteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
chemical_list: D004268:DNA-Binding Proteins; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D009419:Nerve Tissue Proteins; D009842:Oligopeptides; D050809:POU Domain Factors; D010446:Peptide Fragments; D010455:Peptides; C484088:Pou3f4 protein, rat; D012322:RNA Precursors; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins; D014157:Transcription Factors; C085706:FLAG peptide; D005982:Glutathione Transferase