FIGURE 7.

Role of endogenous p53 in TLP-activated transcription from chromosomal p21 upstream promoter. A, two kinds of p21 transcripts produced from the human p21 gene. Positions of exons of p21 variant-1 and p21 alt-a transcripts (48) and genomic DNA around the two p21 promoters are schematically illustrated. Open and solid boxes represent non-coding and coding exons, respectively. Primer sets A, B, and C indicated by thick arrows were used for RT-PCR to detect p21 variant-1, p21 alt-a, and both transcripts, respectively. B, cells were transfected with FH-TLP, and the amounts of p21 transcripts were determined by RT-PCR with each primer set. C, requirement of endogenous p53 for TLP-governed activation of p21 upstream promoter. Wild-type and p53^−/− HCT116 cells (5 × 10⁵) were transfected with FH-TLP (2 μg), and the amount of p21 alt-a transcripts was determined by using primer set B 24 h after transfection. mTLP, mouse TLP.