Homologous DNA recombination mediated by the RAD51 recombinase is a fundamental biological process central to the maintenance of genome stability in dividing human cells. There is considerable topical interest in the biological mechanisms underlying RAD51-mediated reactions in humans. This paper describes a highresolution model for a helical nucleoprotein filament of human RAD51 bound to single-stranded DNA determined by electron cryo-microscopy. The work exemplifies the power of electron cryo-microscopy to resolve the structure of ordered but anisotropic assemblies of relatively small proteins like RAD51, and also reveals several structural features of potential biological importance. In particular, the structure suggests a
mechanism whereby the RAD51-DNA interaction modulates the helical twist and rise of RAD51 protomers assembled in a filament, suggests how disease-associated RAD51 mutations may affect filament assembly, and helps to rationalize potential structural differences bet ...
NAR’s Breakthrough Articles present high-impact studies answering long-standing questions in the field of nucleic acids research and/or opening up new areas and mechanistic hypotheses for investigation. These articles are chosen by the Editors on the recommendation of Editorial Board Members and Referees. Articles are accompanied by a brief synopsis explaining the findings of the paper and where they fit in the broader context of nucleic acids research. They represent the very best papers published at NAR.
This article describes the application of a new imaging technique, called 'phase-plate cryo-EM' for the determination of structures of chromatin-complexes. The 3.9 Å resolution structure of the 200 kDa nucleosome core particle represents the highest resolution structure of a low molecular weight complex determined by this technique. The study demonstrates the expanding potential of cryo-EM as a technique to determine novel structures of ˜200 kDa complexes and dynamic DNA-binding protein complexes. This is important in all fields of nucleic acid research, chromatin structure, replication, DNA repair and transcription. There are many DNA binding proteins that assemble into ˜200 kDa complexes (such as the p53 tetramer, nuclear hormone receptors, telomere-binding proteins and nucleosome-binding proteins) for which only limited structural information exists. These complexes are difficult to crystallize, and at the same time are challenging samples for cryo-EM studies. One important advan ...
The paper describes methodological advances in mitochondrial DNA (mtDNA) mutation detection and applies these methods to track mtDNA mutagenesis following damage induction. Surprisingly, this study demonstrate that mtDNA point and deletion mutation do not increase following mutagen exposure, despite the induction of mtDNA lesions. These findings challenge a long-standing and widely-accepted belief that higher mtDNA mutation rates (compared to nuclear DNA) stem from its inherently greater susceptibility to DNA-damaging agents. Existing assays are have largely been unable to quantitate the accumulation of rare, newly induced mtDNA mutations in response to real-time environmental insults. To overcome this limitation, the authors developed and describe a 'Droplet Digital Random Mutation Capture (dRMC) assay and Digital Deletion Detection (3D) assay to accurately measure the accumulation of point and deletion mutations in mtDNA. By measuring mutation frequencies in mice sub-chronically expo ...
