text: RNA-protein interactions have been investigated through a three-hybrid variation of the two-hybrid technique. In this case, a hybrid RNA molecule serves to adjoin together the two protein fusion domains—which are not intended to interact with each other but rather the intermediary RNA molecule (through their RNA-binding domains). Techniques involving non-fusion proteins that perform a similar function, as described in the non-fusion proteins section above, may also be referred to as three-hybrid methods.