Fig. 1. GFP-PML isoforms are biologically active as growth suppressors. (A) Schematic depiction of the domain structure of PML isoforms (Jensen et al., 2001). All PML isoforms share a common N terminus but differ in their C termini, attributable to the alternative splicing of exons 7 to 9. Protein domains of all PML isoforms include the RING finger (R), the B1 and B2 boxes, the coiled-coil motif (CC), a nuclear localization signal (NLS) and three SUMOylation sites (S). PML VI does not contain the SUMO interacting motif (SIM) within exon 7a. (B) U-2 OS cells were transiently transfected with equal amounts of plasmids expressing GFP, or GFP–PML-I, GFP–PML-II, GFP–PML-III or GFP–PML-VI. Four days after transfection the number of living cells was determined by Trypan-Blue exclusion and normalized to GFP-expressing cells. The diagram shows mean values ± s.d. of three independent experiments.