Bernards A, Van der Ploeg L H, Gibson W C, Leegwater P, Eijgenraam F, De Lange T, Weijers P, Calafat J, Borst P
J Mol Biol. 1986 Jul 5;190(1):1-10. doi: 10.1016/0022-2836(86)90070-7.
To study the evolution of the variant surface glycoprotein (VSG) repertoire of trypanosomes we have analysed the DNA region surrounding the VSG 118 gene in different trypanosome strains. We find a remarkable degree of variation in this area. Downstream from the 118 gene a 5.7 X 10(3) base-pair DNA segment containing a potential VSG gene has been quadruplicated in strain 427 of Trypanosoma brucei, but not in most other strains analysed. The VSG 1.1000 gene, located immediately upstream from the 118 gene in one trypanosome strain, has been cleanly deleted in another. Our results are most easily explained by multiple unequal cross-overs between sister chromatids and are the first indication that sister chromatid exchange occurs in trypanosomes.
为了研究锥虫可变表面糖蛋白（VSG）库的进化，我们分析了不同锥虫菌株中VSG 118基因周围的DNA区域。我们发现该区域存在显著程度的变异。在118基因下游，一个包含潜在VSG基因的5.7×10³碱基对DNA片段在布氏锥虫427菌株中发生了四倍重复，但在大多数其他分析菌株中未出现这种情况。在一个锥虫菌株中位于118基因紧邻上游的VSG 1.1000基因，在另一个菌株中已被完全删除。我们的结果最容易用姐妹染色单体之间的多次不等交换来解释，并且这是锥虫中发生姐妹染色单体交换的首个迹象。
