A FUNCTIONAL-ANALYSIS OF THE GENES ENHANCER OF SPLIT AND HLH-M5 DURING EARLY NEUROGENESIS IN DROSOPHILA-MELANOGASTER

To assess the functional domains of the proteins encoded by E(spl) and HLH-m5, two genes of the Enhancer of split complex [E(SPL)-C] of Dros ophila melanogaster, a number of variants have been made by in vitro m utagenesis, transformed into the germ line of the wild-type, and genet ically combined with a chromosomal deletion lacking four of the genes of the E(SPL)-C. All constructs used attenuated the neurogenic phenoty pe associated with this deletion. However, constructs encoding protein s with truncated carboxy-termini exibited in all cases a higher activi ty than constructs encoding the full length version of the protein. Ne utralization of the basic domain severely reduced, but did not complet ely abolish the rescuing activity of E(spl), while proteins in which a proline residue within the basic domain had been changed to either th reonine or asparagine were slightly less efficient in their rescuing a ctivity than the corresponding wild-type versions. We discuss the poss ible significance of these results for the function of the protein dom ains.