Eukaryotic Cell doi:10.1128/EC.00212-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
Ku-independent end-joining in Trypanosoma brucei cell extracts relies upon sequence microhomology
Peter Burton,
David J. McBride,
Jonathan M. Wilkes,
J. David Barry,
and
Richard McCulloch*
The Wellcome Centre for Molecular Parasitology, University of Glasgow, Glasgow Biomedical Research Centre, 120 University Place, Glasgow, G12 8TA
* To whom correspondence should be addressed. Email:
rmc9z{at}udcf.gla.ac.uk.
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Abstract |
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DNA double strand breaks (DSBs) are repaired primarily by two distinct pathways: homologous recombination and non-homologous end-joining (NHEJ). NHEJ has been found in all eukaryotes examined to date and has been described recently in 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 utilises. 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 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 recognisable homologues of DNA ligase IV or XRCC4, suggesting that NHEJ is either absent or mechanistically diverged in these pathogens.
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