Wiebauer K, Herrero J J, Filipowicz W
Friedrich Miescher-Institut, Basel, Switzerland.
Mol Cell Biol. 1988 May;8(5):2042-51. doi: 10.1128/mcb.8.5.2042-2051.1988.
The report that human growth hormone pre-mRNA is not processed in transgenic plant tissues (A. Barta, K. Sommergruber, D. Thompson, K. Hartmuth, M.A. Matzke, and A.J.M. Matzke, Plant Mol. Biol. 6:347-357, 1986) has suggested that differences in mRNA splicing processes exist between plants and animals. To gain more information about the specificity of plant pre-mRNA processing, we have compared the splicing of the soybean leghemoglobin pre-mRNA with that of the human beta-globin pre-mRNA in transfected plant (Orychophragmus violaceus and Nicotiana tabacum) protoplasts and mammalian (HeLa) cells. Of the three introns of leghemoglobin pre-mRNA, only intron 2 was correctly and efficiently processed in HeLa cells. The 5' splice sites of the remaining two introns were faithfully recognized, but correct processing of the 3' sites took place only rarely (intron 1) or not at all (intron 3); cryptic 3' splice sites were used instead. While the first intron in human beta-globin pre-mRNA was not spliced in transfected plant protoplasts, intron 2 processing occurred at a low level, indicating that some mammalian introns can be recognized by the plant intron-splicing machinery. However, excision of intron 2 proved to be incorrect, involving the authentic 5' splice site and a cryptic 3' splice site. Our results indicate that the mechanism of 3'-splice-site selection during intron excision differs between plants and animals. This conclusion is supported by analysis of the 3'-splice-site consensus sequences in animal and plant introns which revealed that polypyrimidine tracts, characteristic of animal introns, are not present in plant pre-mRNAs. It is proposed that an elevated AU content of plant introns is important for their processing.
有报道称，人类生长激素前体信使核糖核酸（pre-mRNA）在转基因植物组织中未进行加工（A. 巴尔塔、K. 索默格鲁伯、D. 汤普森、K. 哈特穆特、M.A. 马特兹克和A.J.M. 马特兹克，《植物分子生物学》6:347 - 357，1986年），这表明植物和动物之间的信使核糖核酸（mRNA）剪接过程存在差异。为了获取更多关于植物前体信使核糖核酸加工特异性的信息，我们在转染的植物（诸葛菜和烟草）原生质体以及哺乳动物（海拉）细胞中，比较了大豆豆血红蛋白前体信使核糖核酸与人类β-珠蛋白前体信使核糖核酸的剪接情况。在豆血红蛋白前体信使核糖核酸的三个内含子中，只有内含子2在海拉细胞中得到了正确且高效的加工。其余两个内含子的5'剪接位点被忠实地识别，但3'位点的正确加工很少发生（内含子1）或根本不发生（内含子3）；取而代之的是使用了隐蔽的3'剪接位点。虽然人类β-珠蛋白前体信使核糖核酸中的第一个内含子在转染的植物原生质体中未被剪接，但内含子2的加工以低水平发生，这表明一些哺乳动物内含子能够被植物内含子剪接机制识别。然而，内含子2的切除被证明是不正确的，涉及真实的5'剪接位点和一个隐蔽的3'剪接位点。我们的结果表明，内含子切除过程中3'剪接位点选择的机制在植物和动物之间存在差异。对动物和植物内含子中3'剪接位点共有序列的分析支持了这一结论，该分析表明动物内含子特有的多嘧啶序列在植物前体信使核糖核酸中不存在。有人提出，植物内含子中升高的AU含量对其加工很重要。
