Structure of the WT foamyviral genome and the recombinant vectors. (A) Schematic representation of the prototype (formerly human) foamyviral genome with the viral genes gag, pol, env, Tas, and Bet. IP is the internal promoter for the expression of Tas. CAS I and II depict the discontinuous packaging signal residing in the cis-acting sequences I and II. (B) Structures of the recombinant FV self-inactivating vectors MD9-FANCC/EGFP and MD9-EGFP with deletions in gag, pol, env, and the U3 region of the 3′ LTR. SFFV U3 is the promoter of the spleen focus-forming virus U3 region driving the human FANCC and the EGFP cDNAs.