The members of this family are sequences similar to the C-terminal region of RTP801, the protein product of a hypoxia-inducible factor 1 (HIF-1)- responsive gene. Two members of this family expressed by Drosophila melanogaster, Scylla and Charybde, are designated by the GenBank as Hox targets. RTP801 is thought to be involved in various cellular processes. Its overexpression caused the apoptosis- resistant phenotype in cycling cells, and apoptosis sensitivity in growth arrested cells. Moreover, the protein product of the mouse homolog of RTP801 (dig2) is thought to be induced by diverse apoptotic signals, and also by dexamethasone treatment.