Holliday junction resolution
The Holliday junction (HJ) is a key intermediate in homologous recombination. It can be formed both as a consequence of RecA/ Rad51-catalysed strand invasion reactions, and by the reversal of impeded replication forks. HJs constitute physical connections between two DNA duplexes and therefore they have to be removed to enable DNA segregation during cell division. Nucleases, DNA helicases and topoisomerases are variously employed in different strategies of HJ removal, which in turn can influence whether a crossover or non-crossover recombinant DNA molecule is generated. This review will focus on two main types of endonuclease, the HJ resolvases and the Mus81 nucleases, which process HJs and/or related intermediates (e.g. forks, D-loops and nicked HJs). It will describe what is currently known about their mechanisms of action and biological functions. © 2006 Springer-Verlag Berlin Heidelberg.