RELATIONSHIPS BETWEEN TRANSPOSABLE ELEMENTS BASED UPON THE INTEGRASE-TRANSPOSASE DOMAINS - IS THERE A COMMON ANCESTOR

The integrase domain of RNA-mediated elements (class I) and the transp osase domain of DNA-mediated transposable elements (class II) were com pared. A number of elements contain the DDE signature, which plays an important role in their integration. The possible relationships betwee n mariner-Tcl and IS elements, retrotransposons, and retroviruses were analyzed from an alignment of this region. The mariner-Tcl superfamil y, and LTR retrotransposons and retroviruses were found to be monophyl etic groups. However, the IS elements of bacteria were found in severa l groups, These results were used to propose an evolutionary history t hat suggests a common ancestor for some integrases and transposases.