FIG. 1.

Structure of the simplified retroviral vector GCsap and the ADA retroviral vectors. GCsap has the MLV LTR with intact SD and SA sites. The ADA cDNA (ADA) was cloned between NcoI and NotI sites of GCsap to generate ADA(MLV). The 3′ MLV LTR was replaced by the corresponding ClaI-NdeI MPSV or SL3-3 fragment to make ADA(MPSV) or ADA(SL3-3), respectively. Gene sequences present in each vector are labeled as follows: Ψ+, packaging signal; SV, SV40 early promoter; neo, neomycin phosphotransferase gene sequence.