Force-Dependent Facilitated Dissociation Can Generate Protein-DNA Catch Bonds

Cells constantly experience mechanical forces that influence molecular interactions. Most biomolecular bonds behave as slip bonds, where applied forces increase dissociation rates. However, some proteins, like DNA-binding proteins, can undergo facilitated dissociation, where competitor molecules in solution increase dissociation rates. This mechanism raises questions about how force might alter these interactions. Prior research has shown that slip bonds are common, but the role of force in facilitated dissociation is less understood. This gap motivated the development of a model to explore how force might affect these systems. No prior work had resolved the potential for catch bonds in this context. The study addresses the question of whether force can reverse the typical slip-bond behavior in facilitated dissociation systems. This uncertainty drove the need to simulate and analyze the interplay between force and competitor concentration. The paper's contribution is to propose a novel mechanism where force suppresses dissociation in these systems.

The study aimed to investigate how mechanical forces affect the dissociation of DNA-binding proteins undergoing facilitated dissociation. The specific problem is whether applied forces can reverse the typical slip-bond behavior in these systems. The motivation comes from the observation that competitor proteins in solution enhance dissociation, but their interaction with force is unclear. The researchers sought to determine if catch bonds could emerge in such systems. They also aimed to identify the factors regulating the transition between slip- and catch-bond behavior. The study focused on the role of force in inhibiting facilitated dissociation pathways. The goal was to develop a model to explore the interplay between force and molecular geometry. This work addresses a gap in understanding how mechanical signals influence biomolecular interactions.

The researchers used computational simulations and theoretical modeling to analyze the behavior of DNA-binding proteins under force. They developed a generic model to represent the dissociation pathways of these proteins. The model incorporated both spontaneous and facilitated dissociation mechanisms. The simulations tested how applied forces affect the transition energy barriers for each pathway. The team varied parameters such as competitor concentration and protein-DNA geometry. They analyzed how force influences the likelihood of facilitated dissociation. The model allowed them to track the competition between slip- and catch-bond behaviors. The study focused on the regulatory role of force in suppressing facilitated unbinding.

The simulations revealed that catch bonds can form when applied forces suppress dissociation in DNA-binding proteins. This occurs because force inhibits the facilitated dissociation pathway. The catch bond effect emerges when the force dependence of facilitated unbinding is stronger than spontaneous unbinding. The transition between slip- and catch-bond behavior depends on DNA bending by the protein. Higher competitor concentrations in solution increase the likelihood of catch bonds. The sharpness of the transition is regulated by the degree of DNA bending. The model shows that catch bonds are not dependent on specific molecular structures but on external factors like competitor concentration. These findings suggest a novel mechanism for force-dependent regulation of protein-DNA interactions.

The study concludes that force-dependent facilitated dissociation can lead to the formation of catch bonds in DNA-binding proteins. This mechanism is distinct from other catch bonds that rely on intrinsic molecular structures. The catch bond behavior arises from the interplay between force and competitor concentration. The transition between slip- and catch-bond behavior is regulated by DNA bending and competitor levels. The researchers propose that this mechanism could be used by cells to modulate protein exchange and transcription. The findings suggest that force can serve as a regulatory signal in biomolecular interactions. The model supports the hypothesis that catch bonds are broadly regulated by extrinsic factors. These conclusions are based on the simulations and theoretical analysis presented in the paper.