Ikaros: Proteins and Enzymes

Ikaros (also LyF1) is a 60 kDa member of the C2H2-type zinc-finger protein family. It is found in both T and B cells and serves as a context-dependent activator or repressor of genes. Human Ikaros is 519 amino acids (aa) in length. It possesses two zinc-finger domains, one at the N-terminus that contains four zinc-finger motifs (aa 117-224) and one at the C-terminus that contains two zinc-finger motifs (aa 462-514). The C-terminal motifs mediate homo- or heterodimerization, while the N-terminal motifs bind DNA. Multiple splice forms of 37 kDa to 47 kDa exist (Ikaros 2-8) with reduced numbers of N-terminal zinc-finger motifs. At least three are needed for DNA binding, and a heterodimer with a two-motif monomer is suggested to be transcriptionally inert. Over aa 427-519 (which are not spliced), human Ikaros shows 88% aa identity to mouse Ikaros.