DNA-binding protein that binds to the 5'GGGAATRCC-3' Ikaros-binding sequence. Transcriptional repressor. Interacts with SPI1 and MITF to repress transcription of the CTSK and ACP5 promoters via recruitment of corepressors SIN3A and CTBP2. May be involved in the development of central and peripheral nervous systems. Essential for the inhibitory function of regulatory T-cells (Treg). Mediates FOXP3-mediated gene silencing in regulatory T-cells (Treg) via recruitment of corepressor CTBP1 (By similarity). Self-associates. Interacts with other family members; IKZF1, IKZF2, IKZF3 and IKZF5. Interacts with CTBP2. Interacts with SPI1, MITF, FOXP3 and CTBP1 (By similarity). Highly expressed in skeletal muscle, low levels of expression in heart, thymus, kidney, liver, and spleen. Expressed in the hematopoietic cell lines MOLT-4, NALM-6 and K-562. Highly expressed in THP-1 and M-07e cell lines, which have characteristics of myeloid and early megakaryocytic cells respectively. The N-terminal zinc fingers are involved in sequence-specific DNA binding and heterotypic associations with other family members. C-terminal zinc fingers mediate homodimerization. 'Eos' means 'rising sun' in Greek. Belongs to the Ikaros C2H2-type zinc-finger protein family.