The crystal structures of DNA Holliday junctions

Nearly 40 years ago, Holliday proposed a four-stranded complex or junction as the central intermediate in the general mechanism of genetic recombinati on. During the past two years, six single-crystal structures of such DNA ju nctions have been determined by three different research groups. These stru ctures all essentially adopt the antiparallel stacked-X conformation, but c an be classified into three distinct categories: RNA-DNA junctions; ACC tri nucleotide junctions; and drug-induced junctions. Together, these structure s provide insight into how local and distant interactions help to define th e detailed and general physical features of Holliday junctions at the atomi c level.