Eos and Pegasus, two members of the Ikaros family of proteins with distinct DNA binding activities

Members of the Ikaros family of transcription factors, Ikaros, Aiolos, and Hellos, are expressed in lymphocytes and have been implicated in controllin g lymphoid development. These proteins contain two characteristic clusters of zinc fingers, an N-terminal domain important for DNA recognition, and a C-terminal domain that mediates homo- and heterotypic associations between family members. The conservation of these domains is such that all three pr oteins recognize related DNA sequences, and all are capable of dimerizing w ith other family members. Here we describe two additional Ikaros family pro teins, Eos and Pegasus. Eos is most highly related to Hellos and shares its DNA binding and protein association properties. Pegasus is related to othe r Ikaros proteins in its C-terminal dimerization domain but contains a dive rgent N-terminal zinc finger domain, Pegasus self-associates and binds to o ther family members but recognizes distinct DNA-binding sites, Eos and Pega sus repress the expression of reporter genes containing their recognition e lements. Our results suggest that these proteins may associate with previou sly described Ikaros family proteins in lymphoid cells and play additional roles in other tissues.