show Abstracthide AbstractRNA begins to fold as it emerges from an RNA polymerase (RNAP) during transcription. The physical coupling of nascent RNA to RNAP enables a functional interplay between transcription and RNA folding: the 5' to 3' direction of transcription restricts what RNA structures can fold, and conversely, nascent RNA can control transcription by interacting directly with RNAP. To investigate the mechanisms of cotranscriptional RNA structure formation we developed a versatile platform, called Transcription Elongation Complex display (TECdisplay), that systematically measures the activity of RNA sequence variants by quantitatively partitioning a DNA sequence library based on the function of cotranscriptionally displayed RNA. This BioProject contains raw sequence reads from TECdisplay experiments that characterize the mechanisms of Clostridium beijerinckii pfl ZTP riboswitch folding by determining the transcription antitermination activity of 65,536 pfl ZTP riboswitch variants.