..., or through cooperative interaction between PAI domain and HD. However, prd function in vivo requires the synergistic action of both the PAI domain and the HD. Pax proteins with only a PD appear to require both PAI and RED domains, while a Pax-6 isoform and a new Pax protein, Lune, may rely on the RED domain...

..., is distributed in an anterior-to-posterior gradient in the embryo. In response to this gradient, the zygotic gene hunchback is expressed uniformly in the anterior half of the embryo in a nearly all- or-none manner. In this report we demonstrate that a recombinant Bicoid protein binds cooperatively to its sites...