Abstract
The DSL proteins, Serrate and Delta, which act as Notch receptor ligands, mediate signalling between adjacent cells, when a ligand-expressing cell binds to Notch on an adjacent receiving cell. Notch is ubiquitously expressed and DSL protein mis-expression can have devastating developmental consequences. Although transcriptional regulation of Delta and Serrate has been amply documented, we examined whether they are also regulated at the level of translation. We generated a series of deletions to investigate the initiation codon usage for Serrate using Drosophila S2 cells. Serrate mRNA contains three putative ATG initiation codons spanning a 60-codon region upstream of its signal peptide; we found that each one can act as an initiation codon, however, with a different translational efficiency. Serrate expression is strictly regulated at the translational level.
