Biomolecular condensates as nonequilibrium soft materials

Biomolecular condensates are biopolymer bodies within cells thought to act as cellular biochemical organizing centers. The protein-protein, protein-nucleic acid, and nucleic acid-nucleic acid interactions within these membraneless organelles dictate condensate formation, dynamics, and material state. Enzyme activity has been proposed to regulate these interactions and thereby regulate condensate properties, with DEAD-box helicases as a prime candidate class of enzymes for fulfilling this role. In this work, we connect the ATP-dependent RNA helicase activity of a well-studied DEAD-box helicase to the properties of reconstituted condensates. By varying the ability for the RNA substrate to self-interact and through varying chemical energy available to the helicase, we are able to assess the impact of the enzyme's activity on the dynamics and material state of the protein-RNA condensates. Interestingly, enzyme activity also drives mesoscopic structural features of these systems, which are also highly dependent on chemical energy. These results demonstrate how an enzyme can directly impact the dynamics of a biomolecular condensate, revealing broader insights into the interactions that govern condensate structure and dynamics. Furthermore, this system represents a novel class of nonequilibrium soft matter materials with dynamically regulatable properties.