A functional interaction between the histone deacetylase Rpd3 and the corepressor Groucho in Drosophila development

The Drosophila gene groucho (gro) encodes a transcriptional corepressor tha t has critical roles in many development processes. In an effort to illumin ate the mechanism of Gro-mediated repression, we have employed Gro as an af finity reagent to purify Gro-binding proteins from embryonic nuclear extrac ts. One of these proteins was found to be the histone deacetylase Rpd3. Pro tein-protein interaction assays suggest that Gro and Rpd3 form a complex in vivo and that they interact directly via the glycine/proline rich (GP) dom ain in Gro. Cell culture assays demonstrate that Rpd3 potentiates repressio n by the GP domain. Furthermore, experiments employing a histone deacetylas e inhibitor, as well as a catalytically inactive form of Rpd3, imply that h istone deacetylase activity is required for efficient Gro-mediated repressi on. Finally, mutations in gro and rpd3 have synergistic effects on embryoni c lethality and pattern formation. These findings support the view that Gro mediates repression, at least in part, by the direct recruitment of the hi stone deacetylase Rpd3 to the template, where it can modulate local chromat in structure. They also provide evidence for a specific role of Rpd3 in ear ly development.