MDS1 and EVI1 complex locus protein EVI1 (MECOM) also known as ecotropic virus integration site 1 protein homolog (EVI-1) or positive regulatory domain zinc finger protein 3 (PRDM3) is a protein that in humans is encoded by the MECOM gene. EVI1 was first identified as a common retroviral integration site in AKXD murine myeloid tumors. It has since been identified in a plethora of other organisms, and seems to play a relatively conserved developmental role in embryogenesis. EVI1 is a nuclear transcription factor involved in many signaling pathways for both coexpression and coactivation of cell cycle genes.