Gerhards J, Gill A C, Ehrfeld A Y, Dobbelaere D A, Williams R O
Kernforschungszentrum Karlsruhe, Institut für Genetik und für Toxikologie, F.R.G.
Mol Biochem Parasitol. 1989 Apr;34(1):15-24. doi: 10.1016/0166-6851(89)90015-7.
Using a rapid procedure to isolate schizonts of the intracellular parasite Theileria parva from infected bovine lymphocytes, we have prepared parasite RNA that is more than 90% pure. Characterization of this schizont RNA has revealed the presence of two ribosomal RNA species of 3.3 kb and 1.8 kb and a third non-adenylated abundant RNA species of 1.9 kb. In vitro translation of the isolated schizont mRNA has identified about 200 parasite specific polypeptides, only a few of which could be detected by translation of mRNA from infected host cells. By analysing the kinetics of liquid hybridization of schizont mRNA with its homologous complementary DNA the nucleotide sequence complexity of the abundant class of the parasite mRNA has been estimated to be 1.7 x 10(3) kb. Assuming a number average size of 2 kb per mRNA molecule this would represent 4000 transcripts for all abundance classes of the schizont mRNA. Using the same technique we estimate that approximately 10% of the mRNA isolated from infected lymphocytes were transcripts from the parasite genome. We conclude that the low number of parasite specific translation products in the mRNA from infected lymphocytes and the low number of parasite proteins detected in isolated schizonts reported previously is due to the low abundance of the parasite transcripts rather than a low number of expressed parasite genes.
我们采用一种快速方法从感染的牛淋巴细胞中分离细胞内寄生虫小泰勒虫的裂殖体，制备出了纯度超过90%的寄生虫RNA。对这种裂殖体RNA的特性分析显示存在两种分别为3.3 kb和1.8 kb的核糖体RNA以及第三种1.9 kb的非腺苷酸化丰富RNA。对分离出的裂殖体mRNA进行体外翻译，已鉴定出约200种寄生虫特异性多肽，其中只有少数几种可通过感染宿主细胞的mRNA翻译检测到。通过分析裂殖体mRNA与其同源互补DNA的液相杂交动力学，估计寄生虫mRNA丰富类别的核苷酸序列复杂度为1.7×10³ kb。假设每个mRNA分子的数均大小为2 kb，这将代表裂殖体mRNA所有丰度类别的4000个转录本。使用相同技术，我们估计从感染淋巴细胞中分离的mRNA约10%是来自寄生虫基因组的转录本。我们得出结论，先前报道的感染淋巴细胞mRNA中寄生虫特异性翻译产物数量少以及分离的裂殖体中检测到的寄生虫蛋白数量少，是由于寄生虫转录本丰度低而非表达的寄生虫基因数量少。
