Ku heterodimer-independent end joining in Trypanosoma brucei cell extracts relies upon sequence microhomology.
DNA double-strand breaks (DSBs) are repaired primarily by two distinct pathways: homologous recombination and nonhomologous end joining (NHEJ). NHEJ has been found in all eukaryotes examined to date and has been described recently for some bacterial species, illustrating its ancestry. Trypanosoma brucei is a divergent eukaryotic protist that evades host immunity by antigenic variation, a process in which homologous recombination plays a crucial function. While homologous recombination has been examined in some detail in T. brucei, little work has been done to examine what other DSB repair pathways the parasite utilizes. Here we show that T. brucei cell extracts support the end joining of linear DNA molecules. These reactions are independent of the Ku heterodimer, indicating that they are distinct from NHEJ, and are guided by sequence microhomology. We also demonstrate bioinformatically that T. brucei, in common with other kinetoplastids, does not encode recognizable homologues of DNA ligase IV or XRCC4, suggesting that NHEJ is either absent or mechanistically diverged in these pathogens.
Burton
Peter
P
The Wellcome Centre for Molecular Parasitology, University of Glasgow, Glasgow Biomedical Research Centre, Glasgow, Scotland, UK.
McBride
David J
DJ
Wilkes
Jonathan M
JM
Barry
J David
JD
McCulloch
Richard
R
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D034961:Antigens, Nuclear / Q000378:metabolism; D001483:Base Sequence; D002384:Catalysis / Q000187:drug effects; D002457:Cell Extracts; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D017124:Conserved Sequence; D016054:DNA, Protozoan / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D019281:Dimerization; D000072200:Ku Autoantigen; D008274:Magnesium / Q000494:pharmacology; D008969:Molecular Sequence Data; D010802:Phylogeny; D010957:Plasmids; D051135:Rad51 Recombinase / Q000378:metabolism; D011995:Recombination, Genetic / Q000187:drug effects / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D014346:Trypanosoma brucei brucei / Q000166:cytology* / Q000187:drug effects / Q000235:genetics*
D034961:Antigens, Nuclear; D002457:Cell Extracts; D016054:DNA, Protozoan; D004268:DNA-Binding Proteins; D000255:Adenosine Triphosphate; D051135:Rad51 Recombinase; D000072200:Ku Autoantigen; D008274:Magnesium
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