The frequency of gene targeting in Trypanosoma brucei is independent of target site copy number

Nucleic Acids Res. 2003 Jul 15;31(14):3993-4000. doi: 10.1093/nar/gkg445.


We have investigated the effect of target copy number on the efficiency of stable transformation of the protozoan parasite Trypanosoma brucei. Using a single strain of the organism, we targeted integrative vectors to several different genomic sequences, occurring at copy numbers ranging from 1 to approximately 30,000 per diploid genome, and undertook a systematic assessment of both transformation and integration efficiencies. Even over this vast copy number range, frequency of gene targeting was the same for all sites. An independence of targeting frequency and target copy number is characteristic of mammalian homologous recombination and is unlike the situation in budding yeast. It is also not seen in the related parasite Leishmania, a distinction that may be the consequence of the different usage of recombination within the mechanisms of pathogenicity in the two species.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • DNA, Ribosomal Spacer / genetics
  • Gene Dosage
  • Gene Targeting / methods*
  • Genetic Vectors / genetics
  • Genome, Protozoan
  • Molecular Sequence Data
  • Repetitive Sequences, Nucleic Acid / genetics
  • Sequence Homology, Nucleic Acid
  • Transformation, Genetic
  • Trypanosoma brucei brucei / cytology
  • Trypanosoma brucei brucei / genetics*
  • Tubulin / genetics
  • Variant Surface Glycoproteins, Trypanosoma / genetics


  • DNA, Ribosomal Spacer
  • Tubulin
  • Variant Surface Glycoproteins, Trypanosoma