V-ets was found as an oncogenic sequence in the E26 avian retrovirus, which produced leukemias in chickens. There are a large number of mammalian homologues of v-ets, all sharing a common sequence called the ETS domain. These mammalian homologues have been found to be transcriptional activators, and the ETS domain is the DNA binding portion of the gene. This family has been found to be important in regulating embryonic development and the response to growth stimuli. In addition, PU.1 and FLI-1 are dysregulated by Friend leukemia virus insertion in mice resulting in erythroleukemia. Significantly, the DNA binding portion of FLI-1 is the 3' part of an oncogenic fusion transcript (termed EWS-FLI) in human Ewing's sarcoma and neuroepithelioma.