A: Map of the vector pCCL.βwt. PGW used to generate the K562 cellular clones carrying the wild-type and the β039-thal mutated globin mRNA. βp, beta-globin promoter. The three exons, the two introns and the genomic region including the 3′ enhancer are indicated. B: Effects of 400 μg/ml G418 on the production of β-globin in K562-wt3 (D–G) and K562-m5 (H–M). As a reference control, the immunohistochemistry analysis of original wild-type K562 cells (not expressing β-globin mRNA) is shown in panels B and C; analysis performed on untreated (D, E, H, I) versus G418-treated (F, G, L, M) K562-wt3 and K562-m5 cells is shown. Staining of the cells with the β-globin-PE (PE, phycoerythrin) (Santa Cruz Biotechnology, Santa Cruz, CA) is shown in panels C, E, G, I, and M. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]