Hughes D E, Shonekan O A, Simpson L
Department of Biology, University of California, Los Angeles 90024.
Mol Biochem Parasitol. 1989 May 1;34(2):155-66. doi: 10.1016/0166-6851(89)90007-8.
The bifunctional dihydrofolate reductase-thymidylate synthase (DHFR-TS) gene from the monogenetic kinetoplastid protozoan, Crithidia fasciculata, was isolated and characterized. The gene is located on a single chromosome of approximately one megabase, and shows significant sequence similarity to other eukaryotic and prokaryotic DHFR and TS genes. There is a single low-abundance polyadenylated DHFR-TS transcript of approximately 3100 nt. One major miniexon splice site was identified by primer extension analysis. The 5' flanking region of the gene is divergently transcribed and shows strong similarities to a consensus DHFR promoter as well as to other eukaryotic 'housekeeping' gene promoter regions. A sequence downstream of the DHFR promoter consensus region is complementary to the 3' end of the C. fasciculata miniexon-derived RNA. This suggests a means by which the two separately transcribed RNAs may be juxtaposed for trans-splicing. In the 3' flanking region of the DHFR-TS gene, there is a sequence that is present in all of the chromosomes from this species and also from Leishmania tarentolae.
从单细胞动基体原生动物纤细短膜虫中分离并鉴定了双功能二氢叶酸还原酶-胸苷酸合成酶（DHFR-TS）基因。该基因位于一条约1兆碱基的单条染色体上，与其他真核和原核DHFR及TS基因具有显著的序列相似性。存在一个约3100 nt的低丰度多聚腺苷酸化DHFR-TS转录本。通过引物延伸分析鉴定出一个主要的小外显子剪接位点。该基因的5'侧翼区域以相反方向转录，与DHFR启动子共有序列以及其他真核“管家”基因启动子区域具有很强的相似性。DHFR启动子共有区域下游的一个序列与纤细短膜虫小外显子衍生RNA的3'末端互补。这提示了一种使两个分别转录的RNA并列进行反式剪接的方式。在DHFR-TS基因的3'侧翼区域，存在一个在该物种以及杜氏利什曼原虫的所有染色体中都有的序列。
