Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Minireview cung cấp cho các bạn kiến thức về ngành y đề tài: DNA breaks as triggers for antigenic variation in African trypanosomes | Minireview DNA breaks as triggers for antigenic variation in African trypanosomes Sam Alsford David Horn and Lucy Glover Address London School of Hygiene Tropical Medicine Keppel Street London WC1E 7HT UK. Correspondence David Horn. Email Published 8 June 2009 Genome Biology 2009 10 223 doi gb-2009-l0-6-223 The electronic version of this article is the complete one and can be found online at http 2009 10 6 223 2009 BioMed Central Ltd Abstract The DNA repair machinery has been co-opted for antigenic variation in African trypanosomes. New work directly demonstrates that a double-strand break initiates a switch in the expressed variant surface coat. The African trypanosome Trypanosoma brucei is a protozoan parasite of major medical and economic importance. The phenomenon of antigenic variation in T. brucei and some other pathogenic microbes enables them to evade the immune system and persist in the host 1 . In T. brucei antigenic variation depends on expression of a single variant surface glycoprotein VSG from one among multiple expression sites 2 and an archive of more than 1 600 VSG genes 3 . Two principal mechanisms have emerged for the activation of a new VSG duplicative gene conversion into the active expression site and in situ activation of a silent expression site coupled with repression of the one previously active. The former is the dominant mechanism underlying antigenic variation 4 and is the focus of new work reported recently in Nature by Boothroyd et al. 5 . As double-strand breaks DSBs have long been known to initiate genetic recombination processes by facilitating strand invasion it had been proposed that a DSB in the 70 bp repeats adjacent to each VSG gene Figure 1 could initiate the process that copies a new VSG into the active expression site 6 . Boothroyd and colleagues now provide compelling evidence in support of this idea 5 . VSG genes are copied into the active expression site The VSG genes are
