Bonus, a Drosophila homolog of TIF1 proteins, interacts with nuclear receptors and can inhibit beta FTZ-F1-dependent transcription

The Drosophila bonus (bon) gene encodes a homolog of the vertebrate TIF1 tr anscriptional cofactors. bon is required for male viability, molting, and n umerous events in metamorphosis including leg elongation, bristle developme nt, and pigmentation. Most of these processes are associated with genes tha t have been implicated in the ecdysone pathway, a nuclear hormone receptor pathway required throughout Drosophila development. Bon is associated with sites on the polytene chromosomes and can interact with numerous Drosophila nuclear receptor proteins. Bon binds via an LxxLL motif to the AF-2 activa tion domain present in the ligand binding domain of beta FTZ-F1 and behaves as a transcriptional inhibitor in vivo.