p53-dependent suppression of uridine phosphorylase gene expression through direct promoter interaction. | Academic Article individual record

Uridine phosphorylase (UPase) is a key enzyme in the pyrimidine salvage pathway. It reversibly catalyzes the catabolism of uridine to uracil; controls the homeostatic regulation of uridine concentration in plasma and tissues; and plays a role in the intracellular activation of 5-fluorouracil. We cloned the murine UPase gene promoter, a 1703-bp fragment, and determined the transcription initiation sites located at +1 and +92 bp of the cDNA sequence. Through transient expression analysis of the 5'-flanking region of UPase gene, we have evaluated the promoter activity for a series of fragments with 5'- to 3'-deletion in murine breast cancer EMT-6 cells and immortalized murine fibroblast NIH 3T3 cells. Cotransfection of the UPase promoter constructs (from -1619 to -445) containing p53 binding motif with the wild-type p53 construct resulted in a significant reduction of luciferase activity; however, this effect disappeared with the additional deletion of the -445 to -274 sequence to suggest the existence in this promoter region of a putative p53 recognition element. Similar cotransfection in murine embryo fibroblasts p53-/- confirmed the inhibitory role of p53 on the UPase promoter activity. The specificity of the interaction is demonstrated by nuclear protein-specific binding to the putative p53 recognition sequence using gel mobility shift assay and DNase I footprinting analysis. These data indicate the UPase gene is a novel target of p53, and its expression is down-regulated by p53 at the promoter level.

author list (cited authors)
Zhang, D., Cao, D., Russell, R., & Pizzorno, G.
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  • Molecular Sequence Data
  • 3T3 Cells
  • Chromosome Mapping
  • Gene Silencing
  • Base Sequence
  • Pyrimidines
  • Ribonucleotides
  • Tumor Suppressor Protein P53
  • Uridine Phosphorylase
  • Mice
  • Tumor Cells, Cultured
  • Promoter Regions, Genetic
  • Protein Binding
  • RNA, Messenger
  • Animals
  • Transcription, Genetic
  • Gene Expression Regulation, Neoplastic
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