A DROSOPHILA-MELANOGASTER HOMOLOG OF THE HUMAN DEAD-BOX GENE DDX1

DEAD-box genes are found throughout evolution and encode RNA-binding p roteins. Such proteins include eukaryotic initiation factor-4A, which is essential for protein translation, Vasa, which is essential for ger m line development, and a number of nuclear and mitochondrial RNA spli cing factors. Transcription of a human DEAD-box gene, DDX1, is elevate d in two retinoblastoma cell lines as a result of amplification of the immediate chromosomal region surrounding it, suggesting an important role for this gene in control of cell growth and division. We have iso lated a Drosophila melanogaster (Dm) homologue (Ddx1) of DDX1 which is strikingly similar to the human gene. The similarity (58.3% amino aci d (aa) identity over 720 aa) extends beyond regions conserved in all D EAD-box proteins and covers the entire lengths of the proteins. The 2. 7-kb Dm Ddx1 RNA is expressed throughout development, but its levels a re elevated in early embryos. Ddx1 maps to polytene chromosome band 79 D4 on the left arm of Dm chromosome 3.