Alteration of the N-Terminus to analyze Enhancer of Rudimentary Homolog, ERH function

Abstract

The enhancer of rudimentary gene, e(r), is the gene that encodes the Enhancer of Rudimentary Homolog protein (ERH). The amino acid structure of this protein, especially the first five amino acids which make up the N-terminus and the beginning of the first β-strand in the β-sheet of the protein’s secondary structure, have been found to be highly conserved among a wide variety of organisms, including vertebrates, insects, and protists. This suggests that these amino acids may play a key role in the activity of ERH, and that ERH may have a conserved function across organisms. Mutations in amino acids 2 through 5 were constructed and the mutant e(r) alleles were inserted into the third chromosome of Drosophila melanogaster. The activity of the resulting mutant ERH proteins was assessed by their ability to rescue two mutant phenotypes of e(r) deletions – low viability of the single mutant and the synthetic lethality as a double mutant with a low-activity Notch mutation. Phenotypic observations of eye color show whether any of the mutations give rise to wild-type ratios of females versus males. The results indicate that the N-terminus of ERH is indeed necessary for its proper function, and that this function may be evolutionarily conserved.