BENDLESS, A DROSOPHILA GENE AFFECTING NEURONAL CONNECTIVITY, ENCODES A UBIQUITIN-CONJUGATING ENZYME HOMOLOG

The Drosophila bendless (ben) gene was originally isolated as a mutati on affecting the escape jump response. This behavioral defect was ascr ibed to a single lesion affecting the connectivity between the giant f iber and the tergotrochanter motor neuron. A closer examination of the ben phenotype suggests that ben activity is broader and affects a var iety of other neurons including photoreceptor cells and their axons. M osaic analysis indicates that the focus of ben activity is presynaptic . We have cloned the ben gene through a chromosomal walk and show that it is homologous to a class of ubiquitin-conjugating enzymes. The maj or role of ubiquitination in the protein degradative pathway suggests that ben regulates neural developmental processes such as growth cone guidance by targeting specific proteins for degradation.