Professor David Lilley
MSI/WTB Complex
University of Dundee
Dundee, UK

Friday, February 13, 2004
3:00 pm (CT)
3269 Beckman Institute

Abstract

The four-way (Holliday) DNA junction is the central intermediate in homologous genetic recombination. This structure folds in the presence of magnesium ions by pairwise, coaxial stacking of helical arms. The resulting structure has important dynamic properties, involving exchange of stacking partners, and branch migration in the case of homologous junctions. The junction is recognised by a series of proteins, including the resolving enzymes, nucleases targeted to the structure of the branchpoint. The nucleases cleave the DNA in a hydrolysis reaction in which a metal-bound water molecule acts as the nucleophile. Curiously, while these enzymes are highly selective for the structure of the four-way junction, they all distort the structure of the DNA. It is becoming clear that the distortion is important in the function of the enzyme, and that recognition and manipulation of the structure and catalysis of the cleavage of the DNA are intimately related.

Tea and coffee will be served in R3151 Beckman Institute at 2:15pm.