CBP-dependent and independent enhancing activity of steroid receptor coactivator-1 in thyroid hormone receptor-mediated transactivation.
Full-length of steroid receptor coactivator-1 (F-SRC-1) has been shown to interact with thyroid hormone receptors (TRs) in a ligand-dependent manner and to stimulate receptor-dependent transcription. To identify functional domains of F-SRC-1, several internal deletion mutants of F-SRC-1 were constructed. Although in vitro pull down assay with TR showed interaction of all of these mutants with TR, lack of mid legion (amino acids 398-1172) lost enhancing activity of TR-mediated transcription in a transient transfection assay. However, F-SRC-1 mutant lacking CBP-interacting domain still preserved enhancing activity. Surprisingly, F-SRC-1 mutants also increased basal level of viral promoter activity depending upon their deleted region. Yeast activation function assay revealed that these F-SRC-1 mutants had intrinsic activation function when bound to DNA. Analyses of small fragments of F-SRC-1 identified three separable activation domains. In vitro binding assay showed that TBP and TFIIB bound to C-terminal half of F-SRC-1. These results suggest that F-SRC-1 can function via both CBP-dependent and independent manners using various sets of activation domains and that direct interactions between F-SRC-1 and TBP or TFIIB may not be important for CBP-independent transcription.
Ikeda
M
M
Third Department of Internal Medicine, Yamanashi Medical University Tamaho, Japan.
Kawaguchi
A
A
Takeshita
A
A
Chin
W W
WW
Endo
T
T
Onaya
T
T
D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics; D050882:CREB-Binding Protein; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D051548:Histone Acetyltransferases; D008024:Ligands; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D056920:Nuclear Receptor Coactivator 1; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011988:Receptors, Thyroid Hormone / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D017384:Sequence Deletion; D035181:TATA-Box Binding Protein; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology*; D035581:Transcription Factor TFIIB; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D015003:Yeasts / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; D008024:Ligands; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011988:Receptors, Thyroid Hormone; D011993:Recombinant Fusion Proteins; D035181:TATA-Box Binding Protein; D015534:Trans-Activators; D035581:Transcription Factor TFIIB; D014157:Transcription Factors; D050882:CREB-Binding Protein; D051548:Histone Acetyltransferases; D056920:Nuclear Receptor Coactivator 1