RhoBAST is a tiny RNA molecule that activates fluorescent dyes, enabling researchers to track RNA molecules in living cells with super-resolution. An international collaboration, which includes Ronald Micura and his team from the Institute of Organic Chemistry, has now shown that a small, local “nucleotide flip” within the RNA controls this fluorescence activation.

Fluorescent light-up aptamers (FLAPs) are short RNA sequences that bind and activate small dye molecules that otherwise exhibit only weak fluorescence. This enables genetic tagging of RNAs for live-cell imaging without the need for protein fusion markers. Because the dye is only “switched on” upon binding to the RNA, background fluorescence remains low.

Systems such as Spinach, Broccoli, Mango and Pepper have continuously advanced this principle over the past years. RhoBAST additionally enables high-resolution imaging of individual RNA molecules in living cells.