EVI-1 and AML1–MDS1–EVI-1 gene structure. The two protein isoforms generated from the MDS1-EVI-1 gene, MDS1-EVI-1 and EVI-1, differ in their N termini, with MDS1-EVI-1 containing a PR domain that EVI-1 AML1–MDS1–EVI-1 and EVI-1 have oncogenic properties that MDS1–EVI-1 lacks. The gene structure for these isoforms and the location of their functional domains are shown. The role that PR domain– (and SET domain–) containing proteins play in myeloid malignancies is an important area for future investigation.