LUNE EYE GONE, A PAX-LIKE PROTEIN, USES A PARTIAL PAIRED DOMAIN AND AHOMEODOMAIN FOR DNA RECOGNITION

Pax proteins, characterized by the presence of a paired domain, play k ey regulatory roles during development. The paired domain is a biparti te DNA-binding domain that contains two helik-turn-helix domains Joine d by a linker region. Each of the subdomains, the PAI and RED domains, has been shown to be a distinct DNA-binding domain. The PAI domain is the most critical, but in specific circumstances, the RED domain is i nvolved in DNA recognition. We describe a Pax protein, originally call ed Lune, that is the product of the Drosophila eye gone gene (eyg) It is unique among Pax proteins, because it contains only the RED domain. eyg seems to play a role both in the organogenesis of the salivary gl and during embryogenesis and in the development of the eye. A high-aff inity binding site for the Eyg RED domain was identified by using syst ematic evolution of ligands by exponential enrichment techniques. This binding site is related to a binding site previously identified for t he RED domain of the Pax-6 5a isoform. Eyg also contains another DNA-b inding domain, a Prd-class homeodomain (HD), whose palindromic binding site is similar to other Prd-class HDs. The ability of Pax proteins t o use the PAI, RED, and HD, or combinations thereof may be one mechani sm that allows them to be used at different stages of development to r egulate various developmental professes through the activation of spec ific target genes.