Complex cellular logic computation using ribocomputing devices

Synthetic biology aims to develop engineering-driven approaches to program cellular function that could yield transformative technologies(1). Synthetic gene circuits that combine DNA, protein, and RNA components have demonstrated a range of functions including bistability(2), oscillation(3,4), feedback(5,6), and logic capabilities(7–15). However, scaling up these circuits remains challenging due to the limited number of designable, orthogonal, high-performance parts, the empirical and often tedious composition rules, and substantial resource requirements for encoding and operation. Here, we report a strategy for constructing RNA-only nanodevices to evaluate complex logic in living cells. Such ‘ribocomputing’ systems are composed of de-novo-designed parts and operate via predictable and designable base-pairing rules, allowing for effective in silico design of computing devices with prescribed configurations and functions in complex cellular environments. These devices operate at the post-transcriptional level and use an extended RNA transcript to co-localize all circuit sensing, computation, signal transduction, and output elements in the same self-assembled molecular complex, which reduces diffusion-mediated signal losses, lowers metabolic cost, and improves circuit reliability. We demonstrate that ribocomputing devices in E. coli can evaluate two-input logic with dynamic range up to 900-fold and scale them to four-input AND, six-input OR, and a complex 12-input expression (A1 AND A2 AND NOT A1*) OR (B1 AND B2 AND NOT B2*) OR (C1 AND C2) OR (D1 AND D2) OR (E1 AND E2). Successful operation of ribocomputing devices based on programmable RNA interactions suggests that systems employing the same design principles could be implemented in other host organisms or in extracellular settings.