Binding properties of the human homeodomain protein OTX2 to a DNA target sequence

OTX2, a homeodomain protein essential in mouse for the development of structures anterior to rhombomere 3, binds with high affinity to a DNA element (called OTS) present in the human tenascin-C promoter. Here we investigate the binding properties of the full length recombinant human OTX2 and of several deletion mutants to the OTS element. We demonstrate that, upon binding of the protein to its DNA target site, a second molecule of OTX2 is recruited to the complex and that a nearby second binding site is not necessary for this interaction. OTX2 sequences located within a region carboxyl-terminal to the homeodomain are necessary in addition to the homeodomain for binding to DNA. Furthermore, OTX2 dimerization requires the same protein domains necessary for DNA binding.