Wilson, P.M., Fazzone, W., LaBonte, M.J., Lenz, H.J. and Ladner, R.D.
Notes: The authors examined the role of p53 in modulating dUTPase promoter activity. Base substitution mutations of Sp1- and E2F-binding sites in the dUTPase promoter were performed using the GeneEditor™ in vitro Site-Directed Mutagenesis System. Each mutant was confirmed by DNA sequencing. To determine growth inhibition, HCT116 human colon cancer cells were seeded in 96-well plates at 3 × 103 cells/well and treated with 5-fluorouracil (5-FU), fluorodeoxyuridine (FUdR), oxaliplatin or in combination. After 72 hours, the CellTiter® 96 AQueous One Solution was dispensed into each well and absorbance measured. RNA was isolated from HCT116 p53+/+ and HCT116 p53-/- cells. cDNA was reverse transcribed from 200ng total RNA followed by multiplex qPCR using the Plexor™ qPCR System to amplify dUTPase, thymidylate synthase and GAPDH, a housekeeping gene. The 1.2 kb region of the dUTPase promoter upstream of the transcriptional start site was amplified by PCR and the fragment cloned into the pGL3-Basic Vector. Truncated promoters were also generated by PCR and cloned into the same vector. Drosophila SL-2 cells and HCT116 cell lines were seeded in a 24-well plate and transfected with dUTPase pGL3 promoter constructs or with pCI-Neo:p53WT, pCI-Neo:p53MUT and the empty pCI-neo Mammalian Expression Vector; all transfections included the pRL-TK Vector at a ratio of 1:10. After six hours, the cells were incubated in either fresh medium or medium containing a cytotoxic agent at the appropriate concentration. Thirty hours later, the cells were lysed, quantitated by Western blotting and 20µl of lysate analyzed with the Dual-Luciferase® Reporter Assay System. Electrophoretic mobility shift analyses (EMSA) were performed using –64 to –91 of the dUTPase-nuclear isoform transcriptional start site in the Gel Shift Assay System. (4031)