Gfi-1 was first cloned from rats (and subsequently from mice, chickens, and humans) and was found to be a 55-kDa protein that bound to DNA in a sequence-specific manner to act as a transcriptional repressor and proto-oncogene. Using PCR, a Gfi-1 homologous cDNA (mdGfi-1) was cloned from the house fly, Musca domestica. Comparison of the mdGfi-1-deduced amino acid sequence with those of vertebrates indicates only moderate overall homology (40.9-43.0% identity). However, these proteins are highly conserved when the zinc finger domains are compared, with mdGfi-1 having 81.0-82.2% identity to the vertebrate homologues, Within each of the six zinc finger domains there are three amino acids that are predicted to contact the DNA and these amino acids are 100% identical for all six domains for all species. Given that Gfi-1 is highly conserved from insects to vertebrates suggests this may be an important transcription factor in many tare.