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Two pathways of homologous recombination in Trypanosoma brucei
Author(s) -
Conway Colin,
Proudfoot Chris,
Burton Peter,
Barry J. David,
McCulloch Richard
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.03122.x
Subject(s) - biology , rad51 , antigenic variation , homologous recombination , recombination , genetics , gene , genome , trypanosoma brucei , dna , non homologous end joining , homology (biology) , genetic recombination
Summary African trypanosomes are unicellular parasites that use DNA recombination to evade the mammalian immune response. They do this in a process called antigenic variation, in which the parasites periodically switch the expression of VSG genes that encode distinct Variant Surface Glycoprotein coats. Recombination is used to move new VSG genes into specialised bloodstream VSG transcription sites. Genetic and molecular evidence has suggested that antigenic variation uses homologous recombination, but the detailed reaction pathways are not understood. In this study, we examine the recombination pathways used by trypanosomes to integrate transformed DNA into their genome, and show that they possess at least two pathways of homologous recombination. The primary mechanism is dependent upon RAD51, but a subsidiary pathway exists that is RAD51‐independent. Both pathways contribute to antigenic variation. We show that the RAD51‐independent pathway is capable of recombining DNA substrates with very short lengths of sequence homology and in some cases aberrant recombination reactions can be detected using such microhomologies.