Pays E, Lheureux M, Steinert M
Nucleic Acids Res. 1982 May 25;10(10):3149-63. doi: 10.1093/nar/10.10.3149.
The expression-linked copy of the T. b. gambiense variant specific antigen gene LiTat 1.6 is transposed in a 20 kb DNA region devoid of restriction sites, located near a chromosome end. This expression site is very similar to that of T. b. brucei variants 117, 118 (1) and AnTat 1.8. In the basic copy, the transposable element (TE) is flanked by repetitive sequences; it includes the gene copy as well as a sequence of 0.9 to 2.1 kb (probably around 1.1 kb) long, upstream from the gene. Probes derived from the 5' part of the TE specifically reveal three polyadenylated transcripts of 4.2, 1.45 and 0.85 kb, respectively, distinct from the 2.1 kb mRNA. The amount of the 4.2 kb sequence is probably less than 0.01% of total trypanosome RNA. Whereas the mRNAs coding for the three isotypic antigens AnTat 1.8 (T. b. brucei), 12.2 (T. b. rhodesiense) and 3.3 (T. evansi) are recognized by LiTat 1.6 probes extending into the 3' half of the transposed sequence, the 5' genomic probes do not hybridize with any of these RNAs. These observations suggest that the LiTat 1.6 gene could be first transcribed in a large precursor molecule. This precursor would be rapidly processed, loosing a large portion of less conserved sequence from its 5' half. Our data are compatible with a model in which the promoter would be provided by the expression site.
布氏冈比亚锥虫变种特异性抗原基因LiTat 1.6的表达连锁拷贝转座至一个20 kb的无限制酶切位点的DNA区域，该区域位于染色体末端附近。这个表达位点与布氏布氏锥虫变种117、118(1)和AnTat 1.8的表达位点非常相似。在基本拷贝中，转座元件(TE)两侧是重复序列；它包括基因拷贝以及基因上游一段0.9至2.1 kb(可能约1.1 kb)长的序列。源自TE 5'部分的探针分别特异性地揭示了三种多聚腺苷酸化转录本，大小分别为4.2、1.45和0.85 kb，与2.1 kb的mRNA不同。4.2 kb序列的量可能不到锥虫总RNA的0.01%。编码三种同型抗原AnTat 1.8(布氏布氏锥虫)、12.2(布氏罗得西亚锥虫)和3.3(伊氏锥虫)的mRNA可被延伸至转座序列3'半段的LiTat 1.6探针识别，而5'基因组探针与这些RNA均不杂交。这些观察结果表明，LiTat 1.6基因可能首先转录成一个大的前体分子。这个前体将被迅速加工，从其5'半段丢失大部分保守性较低的序列。我们的数据与一种模型相符，即启动子由表达位点提供。
