Four-Way Helical Junctions in DNA Molecules

Abstract

Four-way junctions in DNA Four-way (Holliday) junctions [1] are branchpoints in DNA where four helices are interconnected by the mutual exchange of strands [2] (Figure 1). They are important intermediates in the rearrangement of DNA, and may be created by strand invasion in recombination, double-strand break repair and fork reversal during replication. Additionally, four-way junctions are the central intermediate of the tyrosine recombinases such as Cre [3]. Four-way junctions (and other branched structures) are also important structural and functional elements in RNA, but this aspect will not be considered further here. Nevertheless, many of the conformational principles deduced for the DNA junction apply equally to RNA [4]. This short review focuses on recent developments in understanding the structure and dynamics of DNA four-way junctions.