Confirmation of specificity of interactions observed in yeast 2-hybrid assay. Panels show yeast transformed with a) psoriasin and RanBPM expression plasmids (left) and RanBPM alone (right), and yeast transformed with b) Psoriasin alone, c) psoriasin and empty prey vector, and d) psoriasin with a control gene not isolated in the primary screen. In panels b-d, plates on left are Histidine + (control) and plates on the right are Histidine – (test). Panel a) shows activation of LacZ reporter gene only occurs in yeast transformed with both expression plasmids (left) and no activation in yeast transformed with RanBPM alone (right). Panel b) shows that psoriasin alone cannot activate the Histidine reporter gene as demonstrated by absence of growth on Histidine – plate. Panels c) and d) show that there is a specific interaction necessary for activation of the reporter gene.