Stable gene transfer and tissue-specific expression of a human globin gene using adenoviral vectors

Helper-free double recombinant adenoviruses containing a genomic human globin gene and the neomycin resistance gene (neoR) have been constructed. The inserted globin and neoR genes are stable and transcription of two human globin genes (beta and a hybrid gamma-beta gene) is correctly initiated at the respective globin promoter during lytic infection in 293 cells. The neoR gene driven by the SV40 early promoter confers G418 resistance to human fibroblasts and K562 human erythro-leukemia cells transformed with these viruses. Most neoR clones contain the entire recombinant viral genome, including the inserted globin gene, integrated into their chromosomes. Normally, K562 cells express their gamma but not their beta globin genes. The transferred human beta globin gene was not expressed in either K562 cells or fibroblasts. However, the hybrid gamma-beta globin gene was expressed in all K562 clones that contained the gene whereas gamma-beta mRNA was barely detectable in the fibroblasts. This demonstrates tissue-specific expression of the adenovirus-transferred globin gene. Furthermore, the two transferred genes, globin and neoR, which are situated more than 20 kb apart in the viral genome appear to be independently regulated.