FIG. 8.

Effect of mutations in PTB sites on the function of the PRE in plasmid pDM138, as assessed by CAT RNA levels in the nucleus and cytoplasm. HuH-7 cells were transfected with parental pDM138 or pDM138 containing either wild-type full-length PRE or PRE with mutations in PTB site 1 (mutant 33) or PTB site 2 (mutant 34). After 2 days, total RNA was extracted from the nuclei and cytoplasm of these cells and used for Northern blotting with a ³²P-labeled CAT probe. As an internal control, the blot was washed and reprobed for GAPDH RNA. Similar results were obtained from a duplicate experiment.