Figure 1.

IMPD gene transfer prevents p53-dependent growth suppression. Puromycin-resistant, zinc-dependent, p53-inducible cells (A–C, line Ind-4) and p53-null control cells (D-F, line Con-2) were cotransfected with 2 μg of a plasmid conferring resistance to neomycin and either 5 μg of a plasmid containing a hamster IMPD cDNA driven by the simian virus 40 early promoter (C and F) or 5 μg of a derivative plasmid deleted for the IMPD sequences (A, B, D, and E). Two days after transfection, the cells were trypsinized and replated at 1:10 their initial density into 6-well culture plates containing selective medium (i. e., growth medium containing both puromycin and neomycin; A and D) or selective medium containing 40 μM ZnCl₂ to induce p53 expression (B, C, E, and F). Ten days later cell colonies were stained with crystal violet and photographed. Although not shown here, in the absence of ZnCl₂, IMPD gene transfection did not significantly alter the frequency of resistant colony formation (see Figure 2). (A) p53-inducible line vector transfection, 0 Zn (low p53). (B) p53-inducible line vector transfection + Zn (p53 induced). (C) p53-inducible line IMPD transfection + Zn (p53 induced). (D) p53-null line vector transfection, 0 Zn (no p53). (E) p53-null line vector transfection + Zn (no p53). (F) p53-null line IMPD transfection + Zn (no p53).