Figure 1.
Schematic diagram of the retroviral plasmid constructs. Transgene cassettes were inserted between the LTR-containing elements (U3, R, U5) of a MuLV-derived vector. The MuLV enhancer region was deleted from a sequence (U3) of the 3′ LTR (15), and the αIIb promoter (nucleotides −889 to +35) was used to direct expression of the PlA2β3 or β-gal (nLacZ) in transduced cells. This αIIb promoter segment contains sequences necessary for megakaryocyte-specific expression (7). The immediate-early enhancer/promoter region of the CMV drives gene transcription for retroviral production in the 293 cells (see Materials and Methods). As a positive control, the CMV promoter was used to drive nonspecific expression of β-gal in cells transduced with virions produced from vector pCMVnLacZ.