Integrase, an enzyme encoded by the LTR retrotransposon, then reincorporates the element at a new target site.
Human chromatin-associated protein LEDGF, which tightly binds HIV IN and directs HIV PIC towards highly-expressed genes for integration, is an example of such a host factor.
These undisputed facts, however, were compromised by a good deal of confusion at the time other members entered the scene, for instance the YR recombinases Cre and Flp (capable of integration, excision/resolution as well as inversion), which were nevertheless welcomed as new members of the "integrase family".