Identification and characterization of RRM-containing coactivator activator (CoAA) as TRBP-interacting protein, and its splice variant as a coactivator modulator (CoAM).
We previously cloned and characterized thyroid hormone receptor-binding protein (TRBP) as an LXXLL-containing general coactivator that associates with coactivator complexes through its C terminus. To identify protein cofactors for TRBP action, a Sos-Ras yeast two-hybrid cDNA library was screened using TRBP C terminus as bait. A novel coactivator was isolated, ... coactivator activator (CoAA), that specifically associates with TRBP. Human CoAA is composed of 669 amino acids with a TRBP-interacting domain and two highly conserved RNA recognition motifs (RRM) commonly found in ribonucleoproteins. A splice variant lacking the entire TRBP-interacting domain was also isolated as a coactivator modulator (CoAM), a 156-amino acid protein containing only the RRM region. Human CoAA and CoAM mRNAs are encoded by a single gene located on chromosome 11q13; alternative splicing in exon 2 of CoAA yields CoAM. CoAA interacts with both TRBP and p300 in vitro. In addition, CoAA potently coactivates transcription mediated by multiple hormone-response elements and acts synergistically with TRBP and CREB-binding protein (CBP). Furthermore, CoAA is associated with the DNA-dependent protein kinase-poly(ADP-ribose) polymerase complex. Strikingly, CoAM, which lacks a TRBP-interacting domain, strongly represses both TRBP and CBP action suggesting that CoAM may modulate endogenous CoAA function. These data suggest that CoAA may serve as a mediator of coactivators such as TRBP in gene activation.
Mesh Terms:
Alternative Splicing, Amino Acid Sequence, Amino Acids, Animals, Base Sequence, Carrier Proteins, Cell Nucleus, Cells, Cultured, Chromosomes, Human, Pair 11, Cloning, Molecular, DNA, Complementary, E1A-Associated p300 Protein, Enzyme Activation, Exons, Gene Library, Glutathione Transferase, Humans, Intracellular Signaling Peptides and Proteins, Introns, Mice, Models, Genetic, Molecular Sequence Data, Nuclear Proteins, Plasmids, Poly(ADP-ribose) Polymerases, Protein Binding, Protein Structure, Tertiary, RNA, Messenger, RNA-Binding Proteins, Rats, Recombinant Fusion Proteins, Recombinant Proteins, Sequence Homology, Amino Acid, Temperature, Tissue Distribution, Trans-Activators, Transcription, Genetic, Transfection, Two-Hybrid System Techniques
Alternative Splicing, Amino Acid Sequence, Amino Acids, Animals, Base Sequence, Carrier Proteins, Cell Nucleus, Cells, Cultured, Chromosomes, Human, Pair 11, Cloning, Molecular, DNA, Complementary, E1A-Associated p300 Protein, Enzyme Activation, Exons, Gene Library, Glutathione Transferase, Humans, Intracellular Signaling Peptides and Proteins, Introns, Mice, Models, Genetic, Molecular Sequence Data, Nuclear Proteins, Plasmids, Poly(ADP-ribose) Polymerases, Protein Binding, Protein Structure, Tertiary, RNA, Messenger, RNA-Binding Proteins, Rats, Recombinant Fusion Proteins, Recombinant Proteins, Sequence Homology, Amino Acid, Temperature, Tissue Distribution, Trans-Activators, Transcription, Genetic, Transfection, Two-Hybrid System Techniques
J. Biol. Chem.
Date: Sep. 07, 2001
PubMed ID: 11443112
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