Schematic representation of the MSCV-HS2-β-globin-GFP retroviral vector and its integration into PG13 producer cells (clone H7).

Panel A shows the different parts of the vector,6 which consists of a 5.2-kb fragment flanked with 2 LTRs derived from the MSCV, a human β-globin cassette containing the HS2 domain, the β-globin promoter (βp), and the genomic β-globin gene (3 exons, 2 introns) in reverse orientation. The vector also contains a humanized EGFP gene under the control of a phosphoglycerate kinase (pgk) promoter. A hepatitis B virus posttranscriptional regulatory element (HBPRE) has been inserted to enhance RNA transport from the nucleus. The arrows show the location of the β-globin sequence to which specific primers were made and the 315-bp fragment amplified by RT-PCR for detection of transgene-derived transcripts. ψ indicates the site of the extended packaging signal. Panel B shows a Southern blot ofSstI-digested DNA (left) and HindIII-digested DNA from the PG13 producer cell clone (H7) probed with a GFP probe. TheSstI blot shows a single band corresponding to the expected full-length vector. The HindIII blot indicates that 5 copies of the vector had been integrated into these producer cells.