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首页> 外文期刊>Molecular and Cellular Biology >DNA rearrangements associated with multiple consecutive directed antigenic switches in Trypanosoma brucei.
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DNA rearrangements associated with multiple consecutive directed antigenic switches in Trypanosoma brucei.

机译：与布鲁氏锥虫中多个连续的定向抗原开关相关的DNA重排。

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Changes in variant surface glycoprotein (Vsg) expression allow Trypanosoma brucei to elude the immune response. The expressed vsg is always located at the telomeric end of a polycistronic transcription unit known as an expression site (ES). Although there are many ESs, only one is active at any particular time. The mechanisms regulating ES transcription and switching are unknown. Chromosome rearrangements within or upstream of the ES have been described to occur in occasional switch events, but no changes have been consistently associated with switching. We inserted the drug resistance genes neo and ble, conferring resistance to G418 and phleomycin, respectively, 1 kb downstream of "silent" ES promoters. This demonstrated that short-range transcription could be achieved from a silent ES promoter. From one initial transformant clone, panels of independent consecutive on-off-on switch clones were generated and analyzed. The first activation of the neo-targeted ES was always associated with deletion of the upstream tandem promoter in this ES, but no further rearrangements were detected in consecutive off-on switches of this ES. On the other hand, direct analysis of ES promoters showed that deletions and duplications occurred elsewhere. Activation of a ble-tagged 300-kb chromosome could not be achieved, but phleomycin-resistant clones could be obtained. One such clone arose from recombination between three ESs. Taken together, our experiments suggest that ES switching may occur after a period of chromosomal interactivity that may or may not leave tangible evidence in the form of detectable sequence changes.
机译：变异表面糖蛋白（Vsg）表达的变化使布鲁氏锥虫能够逃避免疫反应。表达的vsg始终位于称为表达位点（ES）的多顺反子转录单位的端粒末端。尽管有许多ES，但在任何特定时间只有一个处于活动状态。调节ES转录和转换的机制尚不清楚。已描述了ES内或上游的染色体重排是在偶发的切换事件中发生的，但没有始终与切换相关联的变化。我们在“沉默” ES启动子的下游1 kb处插入了抗药基因neo和ble，分别赋予了对G418和phleomycin的抗性。这证明可以从沉默的ES启动子获得短距离转录。从一个初始的转化体克隆中，产生并分析了独立的连续的通断开关的克隆。新靶向的ES的首次激活始终与该ES中上游串联启动子的缺失有关，但在该ES的连续断开开关中未检测到进一步的重排。另一方面，对ES启动子的直接分析表明，缺失和重复发生在其他地方。 ble-tagged 300-kb染色体的激活无法实现，但可以获得抗草霉素的克隆。一种这样的克隆是由三个ES之间的重组产生的。综上所述，我们的实验表明，ES转换可能在一段染色体相互作用之后发生，该过程可能会或可能不会以可检测到的序列变化形式留下明显的证据。

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