CHARACTERIZATION OF FUNCTIONAL DOMAINS WITHIN THE MULTIFUNCTIONAL TRANSCRIPTION FACTOR, YY1

YY1 is a multifunctional transcription factor capable of either activa tion or repression of transcription. Using a series of mutant proteins , we have characterized domains responsible for activation or repressi on. We found that the YY1 transcriptional activation domain lies near the amino terminus and requires amino acids 16-29 and 80-100 for maxim al activity. The region between residues 16 and 29 has the potential t o form an acidic amphipathic helix, whereas residues between 80 and 10 0 are rich in proline and glutamine. The YY1 repression domain lies ne ar the carboxyl terminus and is embedded within the YY1 zinc finger re gion necessary for binding to DNA. Deletion of YY1 amino acids, which include zinc fingers 3 and 4, abolishes repression. However, site-dire cted mutagenesis, progressive deletion, and internal deletion mutant a nalyses indicate that the normal structures of zinc fingers 3 and 4 ar e not required for repression.