Rajkovic A, Davis R E, Simonsen J N, Rottman F M
Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, OH 44106.
Proc Natl Acad Sci U S A. 1990 Nov;87(22):8879-83. doi: 10.1073/pnas.87.22.8879.
We present evidence that a subset of mRNAs in the human parasitic trematode Schistosoma mansoni contain an identical 36-nucleotide spliced leader (SL) sequence at their 5' termini. The SL is derived from a 90-nucleotide nonpolyadenylylated RNA (SL RNA), presumably by trans-splicing. Neither the SL nor the SL RNA share significant sequence identity with previously described trans-spliced leaders and SL RNAs in trypanosomatid protozoans or nematodes. However, several features, such as predicted secondary structure, trimethylguanosine cap, and potential Sm binding site, suggest similarities among SL RNAs in widely divergent organisms. Our evidence also indicates that the exon 3 acceptor site of the 3-hydroxy-3-methylglutaryl-CoA reductase gene can be spliced either to the SL by trans-splicing or to an upstream exon, 2, by cis-splicing. The presence of a SL sequence in S. mansoni, a member of the phylum Platyhelminthes, suggests that transplicing may be a common feature of other lower invertebrates.
我们提供的证据表明，人类寄生吸虫曼氏血吸虫中的一部分mRNA在其5'末端含有相同的36个核苷酸的剪接前导序列（SL）。该SL源自一个90个核苷酸的非聚腺苷酸化RNA（SL RNA），推测是通过反式剪接产生的。SL和SL RNA与锥虫原生动物或线虫中先前描述的反式剪接前导序列和SL RNA均无明显的序列同源性。然而，一些特征，如预测的二级结构、三甲基鸟苷帽和潜在结合位点，表明在广泛不同的生物体中SL RNA之间存在相似性。我们的证据还表明，3-羟基-3-甲基戊二酰辅酶A还原酶基因的外显子3受体位点既可以通过反式剪接与SL连接，但也可以通过顺式剪接与上游外显子2连接。扁形动物门成员曼氏血吸虫中存在SL序列，这表明反式剪接可能是其他低等无脊椎动物的一个共同特征。
