Characterization of functional domains within the multifunctional transcription factor, YY1.

YY1 is a multifunctional transcription factor capable of either activation or repression of transcription. Using a series of mutant proteins, we have characterized domains responsible for activation or repression. We found that the YY1 transcriptional activation domain lies near the amino terminus and requires amino acids 16-29 and 80-100 for maximal activity. The region between residues 16 and 29 has the potential to form an acidic amphipathic helix, whereas residues between 80 and 100 are rich in proline and glutamine. The YY1 repression domain lies near the carboxyl terminus and is embedded within the YY1 zinc finger region necessary for binding to DNA. Deletion of YY1 amino acids, which include zinc fingers 3 and 4, abolishes repression. However, site-directed mutagenesis, progressive deletion, and internal deletion mutant analyses indicate that the normal structures of zinc fingers 3 and 4 are not required for repression.