The Regulation of Circular RNA Functions

PROJECT SUMMARY Circular RNAs (circRNAs) are a recently discovered group of single-stranded RNAs that lack ends. The spliceosome complex produces a circRNA by back-splicing precursor mRNA instead of forward-splicing to produce a linear RNA. While the biological functions of circRNAs are distinct from linear RNAs, the mechanisms of how the cell distinguishes between circRNAs and their related linear RNAs, which share the same primary sequence, is not known. During the biogenesis of circRNAs, cells have the opportunity to install post-transcriptional modifications and RNA-binding proteins that mark the RNAs as circular. These “molecular signatures” on circRNAs have the potential to control the cellular trafficking of circRNAs and direct them to locations that are distinct from where their related linear RNAs reside. We hypothesize that cells employ post- transcriptional modifications, cellular localizations, and associated proteins to control circRNA functions. We anticipate that the markers on circRNAs are distinct, which differentiate their roles and fates from their linear RNA counterparts. Over the next five years, we will address how cells regulate the biological roles of circRNAs by answering the following questions: 1) What are the types and levels of post-transcriptional modifications on circRNAs? 2) Where do circRNAs move and reside in the cell? 3) What are the proteins associated with circRNAs? We will compare circRNAs with their linear RNA counterparts to reveal whether and how cells use RNA modifications, regional neighborhoods, and macromolecules to differentiate between RNAs with different topologies that share the same primary sequence. We will employ technologies produced from our previous work as well as molecular and chemical biology approaches. These investigations will produce deep insight into post-transcriptional modifications on circRNAs, an atlas of circRNA cellular trafficking, and proteins specifically associated with circRNAs. Together, the knowledge will establish a fundamental understanding of how cells regulate the functions of circRNAs and distinguish between linear and circRNAs. The proposed project dovetails well with my research group’s long-term vision, which is to illuminate the molecular basis for circRNA functions on a global and single-molecule scale, so that we can address unmet needs in human health.