Retroviral DNA integration: lessons for transposon shuffling.

Phylogenetic comparisons of retroviral IN (integrase) protein sequences have revealed homologies that extend to the retrotransposon and bacterial transposase families and have provided evidence for at least two functional domains. The N-terminal region is characterized by a Zn-finger-like array which is conserved in retrotransposons. The central region is defined by a D,D(35)E amino acid constellation which is conserved through the retrotransposons and several bacterial IS element transposases. Mutagenesis studies and biochemical analysis of the isolated central D,D(35)E domain support our original suggestion that this region contains the catalytic center of these proteins which must all share a similar enzymatic mechanism. These, and other recent findings suggest unexpected relationships between diverse pathways of nucleic acid metabolism in eukaryotes and prokaryotes.