Processing of the polyproteins proceeds by an ordered pathway, called maturation. It involves the initial cleavage of a 27 kDa capsid protein (CA) from the N-terminus of the polyprotein, followed by the cleavage of a 56 kDa integrase (IN) from the C-terminus. This leaves a 72 kDa protease-reverse transcriptase fusion protein (PR-RT), which does not seem to be processed further (By similarity). Retrotransposons are mobile genetic entities that are able to replicate via an RNA intermediate and a reverse transcription step. In contrast to retroviruses, retrotransposons are non-infectious, lack an envelope and remain intracellular. Tf2 retrotransposons belong to the gypsy-like elements (metaviridae).