DNA-binding protein that binds to the 5'GGGAATRCC-3' Ikaros-binding sequence. 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 (PubMed:19696312). Self-associates. Interacts with other family members; IKZF1, IKZF2, IKZF3 AND IKZF5 (By similarity). Interacts with CTBP2, SPI1 and MITF. Interacts with FOXP3 and CTBP1. Expressed mainly in the brain. Up-regulated in long term cultured astrocytes. Down-regulated during osteoclast differentiation. Highly expressed in the brain at 15 dpc and 18 dpc. Expression gradually decreased as postnatal development proceeded. No expression detected in the liver, kidney, lung, thymus or spleen during all developmental stages. The N-terminal zinc fingers are involved in sequence-specific DNA binding. C-terminal zinc fingers mediate homodimerization. Eos is a Greek word for rising sun. Belongs to the Ikaros C2H2-type zinc-finger protein family.