Computational design of sequence-specific DNA-binding proteins.

Sequence-specific DNA-binding proteins (DBPs) play critical roles in biology and biotechnology, and there has been considerable interest in the engineering of DBPs with new or altered specificities for genome editing and other applications. While there has been some success in reprogramming naturally occurring DBPs using selection methods, the computational design of new DBPs that recognize arbitrary target sites remains an outstanding challenge. We describe a computational method for the design of small DBPs that recognize specific target sequences through interactions with bases in the major groove, and employ this method in conjunction with experimental screening to generate binders for 5 distinct DNA targets. These binders exhibit specificity closely matching the computational models for the target DNA sequences at as many as 6 base positions and affinities as low as 30-100 nM. The crystal structure of a designed DBP-target site complex is in close agreement with the design model, highlighting the accuracy of the design method. The designed DBPs function in both Escherichia coli and mammalian cells to repress and activate transcription of neighboring genes. Our method is a substantial step towards a general route to small and hence readily deliverable sequence-specific DBPs for gene regulation and editing.

Preservation of mitochondrial membrane potential is necessary for lifespan extension from dietary restriction.

Dietary restriction (DR) increases lifespan in many organisms, but its underlying mechanisms are not fully understood. Mitochondria play a central role in metabolic regulation and are known to undergo changes in structure and function in response to DR. Mitochondrial membrane potential (Δψm) is the driving force for ATP production and mitochondrial outputs that integrate many cellular signals. One such signal regulated by Δψm is nutrient-status sensing. Here, we tested the hypothesis that DR promotes longevity through preserved Δψm during adulthood. Using the nematode Caenorhabditis elegans, we find that Δψm declines with age relatively early in the lifespan, and this decline is attenuated by DR. Pharmacologic depletion of Δψm blocked the longevity and health benefits of DR. Genetic perturbation of Δψm and mitochondrial ATP availability similarly prevented lifespan extension from DR. Taken together, this study provides further evidence that appropriate regulation of Δψm is a critical factor for health and longevity in response to DR.