Differential expression during embryogenesis of three genes clustered in the Ras1 region of Drosophila melanogaster

Abstract

Transcription mapping and nucleotide sequence analysis reveal that the genomic region of the Drosophila Rasl gene contains a cluster of three closely localized genes. A gene termed Rlbl is located nearby and upstream of Rasl, and is oriented in the opposite polarity relative to Rasl. In addition, a third gene termed Rlcl, is found at a very close proximity downstream to Rlbl. Rasl, the homologue of the human transforming ras genes, has been shown to be active in the posterior termini of the Drosophila embryo and in the eye imaginal disc in pathways of cell fate determination. We demonstrate that during embryogenesis Rasl transcripts are restricted mainly to the embryonic central nervous system, suggesting that the gene product also may have a role in these nerve cells. RZbl encodes for a novel, lysine-rich basic protein. It is expressed mainly in the developing midgut and in the somatic mesoderm. Rlcl also encodes for a novel, basic protein.The expression of Rlcl during embryogenesis is similar, but not identical, to the expression pattern detected for Rasl. The vertebrate p21Ra" proteins are bound to the inner face of the cell membrane. Rasl, the Drosophila homologue of p21, and the Rlbl protein, are also non-cytoplasmic, membranous proteins. Rlbl is found in the cell membrane of larval midgut epithelial cells. In addition, Rlbl is detected in the nuclei of these cells, and in the nuclei of the midgut imaginal cells.

The Ras protein superfamily: Evolutionary tree and role of conserved amino acids

“…S3). Indeed, although they are present in Xenopus, the evolutionarily more ancestral genomes only contain one copy (LET60 in C. elegans and RAS1 in D. melanogaster) that is involved in embryogenesis (Ezer et al, 1994). Fungal orthologous sequences (Fig.…”