In vivo function of a novel Siah protein in Drosophila.

The Siah proteins, mammalian homologues of the Drosophila Sina protein, function as E3 ubiquitin ligase enzymes and target a wide range of cellular proteins for degradation. Here, I investigate the in vivo function of the fly protein, Sina-Homologue (SinaH), which is highly similar to Sina. Flies that completely lack SinaH are viable and in combination with a mutation in the gene, Ebi, show an extra dorsal central bristle phenotype. I also show that SinaH and Ebi can interact with each other both in vivo and in vitro suggesting that they act in the same physical complex. Flies that lack both Sina and Sina-Homologue were also created and show visible eye and bristle phenotypes, which can be explained by an inability to degrade the neuronal repressor, Tramtrack. I find no evidence for redundancy in the function of Sina and SinaH.