FIGURE 1.

Outline of the RNA hybrid system. (A) Schematic representation of the system. Yeast strain YBZ-1 expresses constitutively the fusion protein LexA-MS2 coat-protein. Both lacZ and HIS3 are under the control of multiple lexA operators. When two interacting hybrid RNAs are coexpressed, the MS2–RNA X hybrid binds to the MS2 coat-protein fusion and tethers the RNA Y–m26 fusion RNA to the promoter of lacZ and HIS3, thereby activating gene expression. (B) Overview of plasmids pAN MS2-2 and pIIIa-m26 used in the RNA hybrid system. RNA X and RNA Y can be cloned into pAN MS2-2 (respectively, pIIIa-m26) between the restriction sites XmaI and SphI (SphI and SalI). The schematic structure of the hybrid RNA is shown next to the corresponding plasmid with the positions of the respective restriction sites indicated. (C) Sequence and secondary structure of two pairs of RNAs used in this study.