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首页> 外文期刊>Molecular and Cellular Biology >Metacyclic variant surface glycoprotein genes of Trypanosoma brucei subsp. rhodesiense are activated in situ, and their expression is transcriptionally regulated.
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Metacyclic variant surface glycoprotein genes of Trypanosoma brucei subsp. rhodesiense are activated in situ, and their expression is transcriptionally regulated.

机译：布鲁氏锥虫亚种的元环变异表面糖蛋白基因。罗氏菌原位被激活，其表达受到转录调控。

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During the metacyclic stage in the life cycle of Trypanosoma brucei subsp. rhodesiense, the expression of variant surface glycoproteins (VSGs) is restricted to a small subset of antigenic types. Previously we identified cDNAs for the VSGs expressed in metacyclic variant antigen types (MVATs) 4 and 7 and found that these VSG genes do not rearrange when expressed at the metacyclic stage (M. J. Lenardo, A. C. Rice-Ficht, G. Kelly, K. Esser, and J. E. Donelson, Proc. Nathl. Acad Sci. USA 81:6642-6646, 1984). We now provide further evidence that these genes do not rearrange and demonstrate that their 5' upstream regions lack the 72 to 76-base-pair repeats which are considered the substrate for duplication and transposition events. Pulsed field gradient electrophoresis showed that the MVAT VSG genes were located on the largest chromosome-sized DNA molecules, and the lack of the MVAT 4 gene in one of two different serodemes suggested that one mechanism for the evolution of MVAT repertoires is gene deletion. When MVATs were inoculated into the bloodstream of a mammalian host by a bite from the insect vector, they rapidly switched into nonmetacyclic VSG types. We found that this switch was accomplished by a loss of MVAT RNA concomitant with the loss of metacyclic VSGs. Transcription studies with isolated metacyclic nuclei showed that the MVAT genes were expressed in situ from a single locus and were regulated at the level of transcription.
机译：在布鲁氏锥虫亚种生命周期的中期阶段。罗得岛州，变体表面糖蛋白（VSGs）的表达仅限于抗原类型的一小部分。以前，我们鉴定了以元循环变体抗原类型（MVATs）4和7表达的VSG的cDNA，并发现这些VSG基因在元循环阶段表达时不会重新排列（MJ Lenardo，AC Rice-Ficht，G。Kelly，K。Esser和JE Donelson，美国国家科学院院刊81：6642-6646，1984）。我们现在提供进一步的证据，这些基因没有重新排列，并证明它们的5'上游区域缺少72至76个碱基对的重复序列，这些重复序列被认为是重复和转座事件的底物。脉冲场梯度电泳显示，MVAT VSG基因位于最大的染色体大小的DNA分子上，并且在两个不同的小球菌之一中缺乏MVAT 4基因，这表明MVAT组成谱进化的一种机制是基因缺失。当通过昆虫媒介的叮咬将MVAT接种到哺乳动物宿主的血流中时，它们迅速转变为非元环VSG类型。我们发现，这种转换是通过MVAT RNA的丢失与元环VSG的丢失而实现的。分离的间环核的转录研究表明，MVAT基因是从单个位点原位表达的，并在转录水平受到调控。

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