Laboratory for Interdisciplinary Medical Research, Instituto Oswaldo Cruz - Fiocruz, Av. Brasil, 4365 - Manguinhos, 21045-900 Rio de Janeiro, RJ, Brazil.
Exp Parasitol. 2011 Oct;129(2):203-6. doi: 10.1016/j.exppara.2011.07.004. Epub 2011 Jul 14.
We mapped the 5' UTR for five long hypothetical orfs from Trypanosoma cruzi; each one having a length of more than 10,000 bp. Our aim was to verify the constraints to the length of the 5' UTR and to identify the sites of alternative trans-splicing in the epimastigote stage of three T. cruzi strains. We used reverse transcription PCR to amplify the 5' UTR and demonstrated the transcription of all selected genes as well as additional trans-splicing sites in two of these genes. We observed that the length of the 5' UTR in these genes has a limit, in contrast to previous reports that indicated a trend for longer genes to display a proportionally long 5' UTR. The maximum length of the 5' UTR for the long genes analyzed in the present work is approximately 3% of the orf and, on average, is 1% of the orf length. The poly-pyrimidine tracts used as trans-splicing signal are in the range of 17-53 bases within a distance of 6-59 nt to first spliced-leader acceptor site. T. cruzi populations may use both signals differentially. We conclude that the limit for the 5' UTR length in long genes is determined primarily by the distance to neighboring genes.
我们对来自克氏锥虫的五个长的假设 ORF 的 5'UTR 进行了作图，每个 ORF 的长度都超过 10000bp。我们的目的是验证 5'UTR 长度的约束，并确定三种克氏锥虫株的 动质体阶段中替代转译拼接的位点。我们使用反转录 PCR 来扩增 5'UTR，并证明了所有选定基因的转录以及这两个基因中的另外两个转译拼接位点的转录。我们观察到，这些基因的 5'UTR 长度有一个限制，与之前的报告相反，之前的报告表明，较长的基因显示出相应的长 5'UTR 的趋势。在本工作中分析的长基因的 5'UTR 的最大长度约为 ORF 的 3%，平均为 ORF 长度的 1%。用作转译拼接信号的多嘧啶序列在距第一个拼接先导接受位点 6-59nt 的范围内为 17-53 个碱基。克氏锥虫群体可能会以不同的方式使用这两个信号。我们得出结论，长基因中 5'UTR 长度的限制主要由与邻近基因的距离决定。
