rna three hybrid MI:0438 rna tri hybrid rna 3-hybrid Three hybrid system rna-three hybrid PSI-MI In vivo reconstruction of specific RNA-proteins interactions. The DNA binding and transcription activator domains of GAL4 are brought together via the interaction of recombinant RNA. The first hybrid protein contains the DNA binding domain of GAL4 fused to RevM10 (a mutated RNA binding protein of HIV-1 that binds specifically to the Rev responsive element RRE of the env gene). A recombinant RNA contains the RRE sequence and a target RNA sequence X. The second hybrid protein contains the activation domain of GAL4 fused to protein Y tested for its ability to bind the target RNA X. If this interaction occurs the three hybrid reconstructs GAL4 and the transcription of a reporter gene is activated. three hybrid