The Drosophila protein 'enhancer of rudimentary' (gene (e(r)) is a small protein of 104 residues whose function is not yet clear. From an evolutionary point of view, it is highly conserved []and has been found to exist in probably all multicellular eukaryotic organisms. ERH has been implicated in the regulation of pyrimidine biosynthesis, DNA replication, transcription, mRNA splicing, cellular proliferation, tumorigenesis, and the Notch signaling pathway []. Fission yeast homologue of ERH is implicated in meiotic mRNA elimination during vegetative growth. It forms a stoichiometric complex with Mmi1 to promote meiotic mRNA decay and facultative heterochromatin assembly [, , ]in which the formation of ERH dimer is essential for the complex function.ERH has been shown to interact with SAFB1/SAFB2 (scaffold attachment factor-B 1/2) at the nuclear matrix to regulate SR protein phosphorylation [].
The enhancer of rudimentary gene, e(r), of Drosophila melanogaster encodes an enhancer of rudimentary (ER) protein with functions implicated in pyrimidine biosynthesis and the cell cycle. The ER homologue (ERH) is highly conserved among vertebrates, invertebrates, and plants [].The monomeric structure of ERH comprises a single domain consisting of three α-helices and four β-strands. In the crystal structure, ERH assumes a dimeric structure, through interactions between the β-sheet regions. The long flexible loop is significantly conserved, suggesting that this loop region may be important for the functions of ERH. The putative phosphorylation sites are located at the start of the beta2-strand (Thr18) and at the start of the alpha1-helix (Ser24), implying that the phosphorylation might cause some structural changes [, ].
