Figure 2.

Fluorescence of GFP-expressing cells is specifically reduced by cognate RNA–protein interactions. Cells cotransformed with a GFP indicator plasmid and either plasmid YCpIRP-1 or YCpU1A were grown in glucose or galactose containing medium. The fluorescence of cells grown in glucose (green curves) or galactose (red curves) media was analyzed by flow cytometry. Control cells not carrying a GFP plasmid are represented by the black curves in a and d. Fluorescence drops when expression of the cognate binding protein (b and e) is induced by the addition of galactose. Expression of a noncognate binding protein (a and d) does not affect fluorescence levels. No change of fluorescence is observed with a mutated binding site (c and f) present within the 5′UTR of GFP mRNA. The fluorescence intensity is plotted against counts (number of cells analyzed per channel of fluorescence).