A role for Groucho tetramerization in transcriptional repression.
The Drosophila Groucho (Gro) protein is a corepressor required by a number of DNA-binding transcriptional repressors. Comparison of Gro with its homologues in other eukaryotic organisms reveals that Gro contains, in addition to a conserved C-terminal WD repeat domain, a conserved N-terminal domain, which has previously been implicated in transcriptional repression. We determined, via a variety of hydrodynamic measurements as well as protein cross-linking, that native Gro is a tetramer in solution and that tetramerization is mediated by two putative amphipathic alpha-helices (termed leucine zipper-like motifs) found in the N-terminal region. Point mutations in the leucine zipper-like motifs that block tetramerization also block repression by Gro, as assayed in cultured Drosophila cells with Gal4-Gro fusion proteins. Furthermore, the heterologous tetramerization domain from p53 fully substitutes for the Gro tetramerization domain in transcriptional repression. These findings suggest that oligomerization is essential for Gro-mediated repression and that the primary function of the conserved N-terminal domain is to mediate this oligomerization.
Chen
G
G
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA.
Nguyen
P H
PH
Courey
A J
AJ
D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins / Q000737:chemistry*; D004330:Drosophila / Q000235:genetics*; D005786:Gene Expression Regulation / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009842:Oligopeptides; D010455:Peptides / Q000235:genetics; D017354:Point Mutation / Q000235:genetics; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000235:genetics; D012097:Repressor Proteins / Q000737:chemistry*; D016415:Sequence Alignment; D017421:Sequence Analysis; D014158:Transcription, Genetic / Q000235:genetics*
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D009842:Oligopeptides; D010455:Peptides; D011994:Recombinant Proteins; D012097:Repressor Proteins; C091023:gro protein, Drosophila; C085706:FLAG peptide