FIG. 1.

PTEN repression of RNA Pol I-dependent transcription requires its lipid phosphatase activity. (A) RNA Pol I transcription is decreased by the expression of PTEN but not by a lipid phosphatase-defective mutant PTEN. PTEN and PTEN mutant expression vectors were cotransfected with the RNA Pol I reporter construct, PrHuCAT, into LnCap or U87 cells. RNA was isolated, and promoter activity was measured using a primer extension assay as described in Materials and Methods. An example of the resulting autoradiograph is shown above each graph. (B) TBP promoter activity is not affected by PTEN expression. A human TBP promoter-luciferase construct, p−4500/+66 hTBP-luc, was cotransfected with the PTEN or PTEN mutant plasmids into U87 cells as indicated. Lysates prepared from the transfected cells were assayed for luciferase activity. The values shown are the means ± SEM for four independent experiments. (C) Transcriptional repression is correlated with the down-regulated activation of AKT mediated by PTEN. U87 cells were transfected with the PTEN constructs as indicated, lysates were prepared, and immunoblot analysis was carried out using antibodies against the indicated proteins.