Pays E, Coquelet H, Tebabi P, Pays A, Jefferies D, Steinert M, Koenig E, Williams R O, Roditi I
Department of Molecular Biology, University of Brussels, Belgium.
EMBO J. 1990 Oct;9(10):3145-51. doi: 10.1002/j.1460-2075.1990.tb07512.x.
The variant surface glycoprotein (VSG) and procyclin are the major surface proteins of the bloodstream and procyclic stages, respectively, of Trypanosoma brucei. The promoter regions of the VSG and procyclin gene transcription units could be mapped thanks to the specific enrichment of initial transcripts that occurs following UV irradiation. Whereas the VSG gene is 45 kb distant from its promoter, procyclin genes are located immediately downstream. We show, by run-on assays on isolated nuclei and by cDNA analysis, that transcription occurs from both promoters in bloodstream as well as in procyclic forms. It is inferred that the control of the stage-specific expression of VSG and procyclin genes is not effected at the level of transcription initiation, but most probably by interfering with the elongation and stability of the specific transcripts.
变异表面糖蛋白（VSG）和前环素分别是布氏锥虫血流期和前循环期的主要表面蛋白。由于紫外线照射后初始转录本的特异性富集，VSG和前环素基因转录单元的启动子区域得以定位。VSG基因与其启动子相距45 kb，而前环素基因紧邻其下游。我们通过对分离细胞核的连续转录分析和cDNA分析表明，在血流期和前循环期，两个启动子均有转录发生。由此推断，VSG和前环素基因阶段特异性表达的调控并非发生在转录起始水平，而很可能是通过干扰特定转录本的延伸和稳定性来实现的。
