Functional interaction of the c-Myc transactivation domain with the TATA binding protein: evidence for an induced fit model of transactivation domain folding.
c-Myc is a member of a family of sequence specific-DNA binding proteins that are thought to regulate the transcription of genes involved in normal cell growth, differentiation, and apoptosis. In order to understand how human c-myc functions as a transcription factor, we have studied the mechanism of action and structure ... of the N-terminal transactivation domain, amino acids 1-143. In a protein interaction assay, c-myc1-143 bound selectively to two basal transcription factors, the TATA binding protein (TBP) and the RAP74 subunit of TFIIF. Furthermore, the isolated c-myc transactivation domain competed for limiting factors required for the assembly of a functional preinitiation complex. This squelching of basal transcription was reversed in a dose-dependent manner by recombinant TBP. Taken together, these results identify TBP as an important target for the c-myc transactivation domain, during transcriptional initiation. Similar to other transactivation domains, the c-myc1-143 polypeptide showed little or no evidence of secondary structure, when measured by circular dichroism spectroscopy (CD) in aqueous solution. However, significant alpha-helical conformation was observed in the presence of the hydrophobic solvent trifluoroethanol. Strikingly, addition of TBP caused changes in the CD spectra consistent with induction of protein conformation in c-myc1-143 during interaction with the target factor. This change was specific for TBP as a similar effect was not observed in the presence of TFIIB. These data support a model in which target factors induce or stabilize a structural conformation in activator proteins during transcriptional transactivation.
Mesh Terms:
Amino Acid Sequence, Bacterial Proteins, Base Sequence, Circular Dichroism, DNA Primers, DNA-Binding Proteins, Humans, Molecular Sequence Data, Peptide Fragments, Protein Conformation, Protein Folding, Protein Structure, Secondary, Proto-Oncogene Proteins c-myc, Recombinant Fusion Proteins, Repressor Proteins, Serine Endopeptidases, TATA Box, TATA-Box Binding Protein, Transcription Factors, Transcription Factors, TFII, Transcription, Genetic, Transcriptional Activation
Amino Acid Sequence, Bacterial Proteins, Base Sequence, Circular Dichroism, DNA Primers, DNA-Binding Proteins, Humans, Molecular Sequence Data, Peptide Fragments, Protein Conformation, Protein Folding, Protein Structure, Secondary, Proto-Oncogene Proteins c-myc, Recombinant Fusion Proteins, Repressor Proteins, Serine Endopeptidases, TATA Box, TATA-Box Binding Protein, Transcription Factors, Transcription Factors, TFII, Transcription, Genetic, Transcriptional Activation
Biochemistry
Date: Jul. 23, 1996
PubMed ID: 8755740
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