A Conserved Motif in Goosecoid Mediates Groucho-Dependent Repression in Drosophila Embryos

Abstract

Surprisingly small peptide motifs can confer critical biological functions. One example is the WRPW tetrapeptide present in the Hairy family of transcriptional repressors, which mediates recruitment of the Groucho (Gro) corepressor to target promoters. We recently showed that Engrailed (En) is another repressor that requires association with Gro for its function. En lacks a WRPW motif; instead, it contains another short conserved sequence, the En homology region 1 (eh1)/GEH motif, that is likely to play a role in tethering Gro to the promoter. Here, we characterize a repressor domain from the Goosecoid (Gsc) developmental regulator that includes an eh1/GEH-like motif. We demonstrate that this domain (Gsc^R) mediates efficient repression in Drosophila blastoderm embryos and that repression by Gsc^R requires Gro function. Gsc^Rand Gro interact in vitro, and the eh1/GEH motif is necessary and sufficient for the interaction and for in vivo repression. Because WRPW- and eh1/GEH-like motifs are present in different proteins and in many organisms, the results suggest that interactions between short peptides and Gro represent a widespread mechanism of repression. Finally, we investigate whether Gro is part of a stable multiprotein complex in the nucleus. Our results indicate that Gro does not form stable associations with other proteins but that it may be able to assemble into homomultimeric complexes.

ACKNOWLEDGMENTS

We thank members of our laboratories for their support and encouragement; in particular we are indebted to S. Pinchin for her help with the experiments shown in Fig. 2 and to Katerina Katsani for the gift of purified recombinant Gro. We are also grateful to Z. Paroush for many helpful discussions, to C. Desplan, C. Mailhos, and J. Jaynes for communicating unpublished results, and to C. Mailhos and C. Desplan for Gsc plasmids.

G.J. was supported by the EC Human Capital and Mobility Programme, the Imperial Cancer Research Fund, and EMBO. This work was supported by the Imperial Cancer Research Fund and a grant from the Howard Hughes Medical Institute through the International Research Scholars Program.