Creating Small Transcription Activating RNAs

RNA is an essential biomolecule for many of life’s processes. Amongst its numerous roles, is RNA’s ability to act as a regulator of gene expression. In bacteria, small RNAs (sRNAs) have proven to be a particularly versatile class of gene expression regulator able to control numerous points of gene expression. However, no naturally occurring sRNA has been shown to directly activate transcription in bacteria. Recently we have addressed this gap by creating the first Small Transcription Activating RNAs called STARs. The STAR system involves placing a special RNA sequence (called a transcriptional terminator) upstream of a target gene that acts as a blockade and prevents the cell from transcribing that gene. When the STAR is present, it removes this blockade, turning on the downstream gene by allowing transcription to take place. This mechanism was shown to be general, enabling the design of several STARs which were shown to be highly orthogonal to each other and RNA transcription repressors. This further allowed the construction of higher order devices such as RNA-only logic gates. Through characterization of STAR variants, design rules were created which capture the essence of how STAR sequence affects its function. Finally, we present recent work in increasing the number of orthogonal STAR regulators available, including de novo design strategies that could ultimately lead to larger libraries of this new class of regulator.