IKAROS Family Zinc Finger Protein 4 (IKZF4)

Eos has 2 conserved zinc finger clusters, but it has little homology in its other regions to Ikaros family proteins. GST pull-down experiments showed that the C-terminal zinc fingers of Eos interact with other Ikaros proteins and with Eos itself, establishing the presence of functional dimerization domains. DNA binding analysis indicated that Eos, but not Pegasus, interacts with high affinity with sequences similar to those bound by Ikaros and other family members. Reporter analysis demonstrated that Eos acts as a transcriptional repressor at its sites but not at Pegasus sites. Northern blot analysis revealed highest expression of an approximately 5.0-kb Eos transcript in myeloid and early megakaryocyte cell lines. In tissues, highest expression of Eos was in skeletal muscle, with detectable levels in heart, thymus, kidney, liver, and spleen.