Replicating both ways

Archeal DNA replication proteins are closely related to eukaryotic counterparts, but in the June 23 Science Myllykallio et al. report that the archeon Pyrococcus abyssi has a bacterial mode of replication (Science 2000, 288:2212-2215). Myllykallio et al. use the excess of G over C in the leading replication strand to identify a single origin of bi-directional replication in Pyrococcus. A comparison with a related archeon reveals that, as in bacteria, the replication terminus is a hotspot of genome shuffling. These two similarities with bacteria may be evidence for either convergent evolution or conservation of replication characteristics from the time of a common ancestor.