Functional analysis of pyrimidine biosynthesis enzymes using the anticancer drug 5-fluorouracil in Caenorhabditis elegans

FEBS J. 2009 Sep;276(17):4715-26. doi: 10.1111/j.1742-4658.2009.07168.x. Epub 2009 Jul 23.


Pyrimidine biosynthesis enzymes function in many cellular processes and are closely associated with pyrimidine antagonists used in cancer chemotherapy. These enzymes are well characterized from bacteria to mammals, but not in a simple metazoan. To study the pyrimidine biosynthesis pathway in Caenorhabditis elegans, we screened for mutants exhibiting resistance to the anticancer drug 5-fluorouracil (5-FU). In several strains, mutations were identified in ZK783.2, the worm homolog of human uridine phosphorylase (UP). UP is a member of the pyrimidine biosynthesis family of enzymes and is a key regulator of uridine homeostasis. C. elegans UP homologous protein (UPP-1) exhibited both uridine and thymidine phosphorylase activity in vitro. Knockdown of other pyrimidine biosynthesis enzyme homologs, such as uridine monophosphate kinase and uridine monophosphate synthetase, also resulted in 5-FU resistance. Uridine monophosphate kinase and uridine monophosphate synthetase proteins are redundant, and show different, tissue-specific expression patterns in C. elegans. Whereas pyrimidine biosynthesis pathways are highly conserved between worms and humans, no human thymidine phosphorylase homolog has been identified in C. elegans. UPP-1 functions as a key regulator of the pyrimidine salvage pathway in C. elegans, as mutation of upp-1 results in strong 5-FU resistance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antimetabolites, Antineoplastic / pharmacology*
  • Caenorhabditis elegans / drug effects*
  • Caenorhabditis elegans / enzymology
  • Caenorhabditis elegans / genetics
  • Drug Resistance
  • Fluorouracil / pharmacology*
  • Gene Knockdown Techniques
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism*
  • Mutation
  • Nucleoside-Phosphate Kinase / genetics
  • Nucleoside-Phosphate Kinase / metabolism*
  • Orotate Phosphoribosyltransferase / genetics
  • Orotate Phosphoribosyltransferase / metabolism*
  • Orotidine-5'-Phosphate Decarboxylase / genetics
  • Orotidine-5'-Phosphate Decarboxylase / metabolism*
  • Polymorphism, Single Nucleotide
  • Pyrimidines / biosynthesis*
  • Uridine Phosphorylase / genetics
  • Uridine Phosphorylase / metabolism*


  • Antimetabolites, Antineoplastic
  • Multienzyme Complexes
  • Pyrimidines
  • uridine 5'-monophosphate synthase
  • Orotate Phosphoribosyltransferase
  • Uridine Phosphorylase
  • uridine monophosphate kinase
  • Nucleoside-Phosphate Kinase
  • Orotidine-5'-Phosphate Decarboxylase
  • pyrimidine
  • Fluorouracil