The invention provides methods and kits suitable for large-scale in vivo screening of polypeptides for specific binding affinity to a selected RNA recognition sequence. Polypeptide(s) are screened as fusion proteins with a polypeptide having antitermination activity. Polypeptides having binding activity are identified by their capacity to activate transcription of a reporter gene via binding of the polypeptide being screened to the selected RNA recognition sequence. The invention also provides methods of screening RNA molecules for binding to a selected polypeptide.
