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
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Amino Acid Sequence
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Animals
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Binding Sites
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Blotting, Western
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Cell Nucleus / metabolism
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DNA-Binding Proteins*
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Gene Expression
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Glutathione Transferase
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Heterogeneous-Nuclear Ribonucleoprotein U
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Heterogeneous-Nuclear Ribonucleoproteins
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Hypothalamus / metabolism
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Molecular Sequence Data
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Nerve Tissue Proteins*
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Nervous System / metabolism*
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Oligopeptides
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POU Domain Factors
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Peptide Fragments / chemistry
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Peptides
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Polymerase Chain Reaction
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Protein Binding
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Protein Multimerization
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RNA Precursors / metabolism
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Rats
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / isolation & purification
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Recombinant Fusion Proteins / metabolism
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Ribonucleoproteins / chemistry
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Ribonucleoproteins / isolation & purification
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Ribonucleoproteins / metabolism*
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Transcription Factors / chemistry
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Transcription Factors / isolation & purification
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Transcription Factors / metabolism*
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Transcription, Genetic
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Two-Hybrid System Techniques
Substances
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DNA-Binding Proteins
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Heterogeneous-Nuclear Ribonucleoprotein U
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Heterogeneous-Nuclear Ribonucleoproteins
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Nerve Tissue Proteins
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Oligopeptides
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POU Domain Factors
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Peptide Fragments
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Peptides
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Pou3f4 protein, rat
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RNA Precursors
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Recombinant Fusion Proteins
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Ribonucleoproteins
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Transcription Factors
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FLAG peptide
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Glutathione Transferase