Map of the retroviral vector GC-(anti–Tat/Rev) SN^DC. The vector contains an antisense Tat/Rev gene that encompasses the entire Rev sequence and the second exon of the Tat gene. The antisense gene is expressed from a MoMLV 5′LTR. The vector also contains the neomycin resistance gene (Neo^R) driven by the SV40 early promoter.