Figure 4. There are approximately 20–40 molecules of hTERT mRNA per cell.

A. The in vitro transcribed deletion hTERT RNA was added to total cellular mRNA from A431 cells in varying amounts to generate a titration curve between 1×10⁴ and 1×10⁷ molecules of competitive RNA. This RNA sample was reverse transcribed so that both competitor and endogenous hTERT could be amplified in the same PCR reaction to determine the initial amount of hTERT mRNA present in the reaction. B. The forward primer was radiolabeled and hTERT RT-PCR of total A431 RNA was performed in the presence of hTERT competitive deletion constructs. Samples were separated on a 4% denaturing acrylamide sequencing gel. The identity of each band is indicated by the exon structure to the right. The amplicon is indicated by the dotted line above the diagrams. Data are representative of at least two independent experiments. DEL, deletion; INS, insertion; e, exon; i, intron.