Analysis of the DNA-binding and activation properties of the human transcription factor AP-2.
The mammalian transcription factor AP-2 is a sequence-specific DNA-binding protein expressed in neural crest lineages and regulated by retinoic acid. Here we report a structure/function analysis of the DNA-binding and transcription activation properties of the AP-2 protein. DNA contact studies indicate that AP-2 binds as a dimer to a palindromic recognition sequence. Furthermore, cross-linking and immunoprecipitation data illustrate that AP-2 exists as a dimer even in the absence of DNA. Examination of cDNA mutants reveals that the sequences responsible for DNA binding are located in the carboxy-terminal half of the protein. In addition, a domain mediating dimerization forms an integral component of this DNA-binding structure. Expression of AP-2 in mammalian cells demonstrates that transcriptional activation requires an additional amino-terminal domain that contains an unusually high concentration of proline residues. This proline-rich activation domain also functions when attached to the heterologous DNA-binding region of the GAL4 protein. This study reveals that although AP-2 shares an underlying modular organization with other transcription factors, the regions of AP-2 involved in transcriptional activation and DNA binding/dimerization have novel sequence characteristics.
Williams
T
T
Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Tjian
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R
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D015345:Oligonucleotide Probes; D010957:Plasmids; D012689:Sequence Homology, Nucleic Acid; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection
D004268:DNA-Binding Proteins; D015345:Oligonucleotide Probes; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D004247:DNA