Targeted localized degradation of Paired protein in Drosophila development

Background: Selective spatial regulation of gene expression lies at the cor e of pattern formation in the embryo. In the fruit fly Drosophila, localize d transcriptional regulation accounts for much of the embryonic pattern. Results: We identified a gene, partner of paired (ppa), whose properties su ggest that localized receptors for protein degradation are integrated into regulatory networks of transcription factors to ensure robust spatial regul ation of gene expression. We found that the Ppa protein interacts with the Pax transcription factor Paired (Prd) and contains an F-box, a motif found in receptors for ubiquitin-mediated protein degradation. In normal developm ent, Prd functions only in cells in which ppa mRNA expression has been repr essed by another segmentation protein, Even-skipped (Eve). When ppa was exp ressed ectopically in these cells, Prd protein, but not mRNA, levels dimini shed. When ppa function was removed from cells that express prd mRNA, Prd p rotein levels increased. Conclusions: Ppa co-ordinates Prd degradation and is important for expressi on of Prd to be correctly localized. In the presence of Ppa, Prd protein is targeted for degradation at sites where its mis-expression would disrupt d evelopment. In the absence of Ppa, Prd is longer-lived and regulates downst ream target genes.