Observing spontaneous branch migration of Holliday junctions one step at a time
AUTOR(ES)
McKinney, Sean A.
FONTE
National Academy of Sciences
RESUMO
Genetic recombination occurs between homologous DNA molecules via a four-way (Holliday) junction intermediate. This ancient and ubiquitous process is important for the repair of double-stranded breaks, the restart of stalled replication forks, and the creation of genetic diversity. Once formed, the four-way junction alone can undergo the stepwise exchange of base pairs known as spontaneous branch migration. Conventional ensemble assays, useful for finding average migration rates over long sequences, have been unable to examine the affect of sequence and structure on the migration process. Here, we present a single-molecule spontaneous branch migration assay with single-base pair resolution in a study of individual DNA junctions that can undergo one step of migration. Junctions exhibit markedly different dynamics of exchange between stacking conformers depending on the point of strand exchange, allowing the moment at which branch migration occurs to be detected. The free energy landscape of spontaneous branch migration is found to be highly nonuniform and governed by two types of sequence-dependent barriers, with unmediated local migration being up to 10 times more rapid than the previously deduced average rate.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=556122Documentos Relacionados
- The Bloom's syndrome gene product promotes branch migration of Holliday junctions
- A method for preparing genomic DNA that restrains branch migration of Holliday junctions
- Direct observation of RuvAB-catalyzed branch migration of single Holliday junctions
- RuvAB-directed branch migration of individual Holliday junctions is impeded by sequence heterology
- Branch migration of Holliday junctions: identification of RecG protein as a junction specific DNA helicase.