WINGLESS SIGNAL AND ZESTE-WHITE-3 KINASE TRIGGER OPPOSING CHANGES IN THE INTRACELLULAR-DISTRIBUTION OF ARMADILLO

wingless/wnt-1 signaling directs cell fate during development. Genetic analysis in Drosophila identified genes that may encode components of the wingless signal transduction system. Drosophila Armadillo, homolo g of vertebrate beta-catenin, is required for wingless signaling. Unli ke armadillo RNA, Armadillo protein accumulates non-uniformly in diffe rent cells of each embryonic segment. We found that cells alter their intracellular distribution of Armadillo in response to Wingless signal , accumulating increased levels of cytoplasmic Armadillo relative to t hose of membrane-associated protein. Levels of cytoplasmic Armadillo a re also regulated by Zeste-White 3 kinase. Analysis of double mutants demonstrates that Armadillo's role in wingless signaling is direct, an d that Armadillo functions downstream of both wingless and zeste-white 3. We present a model for the role of Armadillo stripes in transducti on of wingless signal.