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.
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Lilly Research Laboratories, Department of Gene Regulation, Bone and Inflammation Research, Eli Lilly and Company, Indianapolis, Indiana 46285, USA.
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D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D002880:Chromosomes, Human, Pair 11; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D050881:E1A-Associated p300 Protein; D004789:Enzyme Activation; D005091:Exons; D015723:Gene Library; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007438:Introns; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D014018:Tissue Distribution; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D020798:Two-Hybrid System Techniques; D000099253:Trans-Activation Responsive RNA-Binding Protein
D000596:Amino Acids; D002352:Carrier Proteins; D018076:DNA, Complementary; D050881:E1A-Associated p300 Protein; D005982:Glutathione Transferase; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D011065:Poly(ADP-ribose) Polymerases; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D015534:Trans-Activators; D000099253:Trans-Activation Responsive RNA-Binding Protein; C436317:RBM14 protein, human; C486667:Rbm14 protein, rat; C494361:Ep300 protein, mouse; C494362:Ep300 protein, rat