Hoeijmakers J H, Frasch A C, Bernards A, Borst P, Cross G A
Nature. 1980 Mar 6;284(5751):78-80. doi: 10.1038/284078a0.
Pathogenic African trypanosomes evade the immune system of their mammalian hosts by the sequential expression of alternative cell-surface glycoproteins (reviewed in refs 1,2). Variant surface glycoproteins (VSGs) purified from cloned variants of Trypanosoma brucei have similar molecular weights (about 60,000), but differ in amino acid composition, N-terminal amino acid sequence and C-terminal structure. We have cloned DNA complementary to the messenger RNA's for four immunologically distinct VSGs and hybridised these complementary DNAs (cDNAs) with restriction digests of T. brucei nuclear DNA, fractionated by gel electrophoresis and transferred to nitrocellulose strips. Each cDNA recognises a unique set of fragments and this basic set is present unaltered in the nuclear DNAs from the four variants. In addition, each probe recognises an extra fragment only in nuclear DNA isolated from cells expressing the VSG corresponding to the cDNA probe. We infer that activation of a VSG gene involves the production of an expression-linked copy of that gene.
致病性非洲锥虫通过依次表达交替的细胞表面糖蛋白来逃避其哺乳动物宿主的免疫系统（参考文献1、2中有综述）。从布氏锥虫的克隆变体中纯化得到的可变表面糖蛋白（VSG）具有相似的分子量（约60,000），但氨基酸组成、N端氨基酸序列和C端结构有所不同。我们克隆了与四种免疫上不同的VSG的信使RNA互补的DNA，并将这些互补DNA（cDNA）与经凝胶电泳分离并转移至硝酸纤维素膜条上的布氏锥虫核DNA的限制性酶切片段进行杂交。每个cDNA识别一组独特的片段，并且这一基本片段组在来自这四个变体的核DNA中保持不变。此外，每个探针仅在从表达与该cDNA探针相对应的VSG的细胞中分离得到的核DNA中识别一个额外的片段。我们推断VSG基因的激活涉及该基因的一个表达相关拷贝的产生。
