Zinoviev Alexandra, Shapira Michal
Department of Life Sciences, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel.
Comp Funct Genomics. 2012;2012:813718. doi: 10.1155/2012/813718. Epub 2012 Jul 8.
Trypanosomatids are ancient eukaryotic parasites that migrate between insect vectors and mammalian hosts, causing a range of diseases in humans and domestic animals. Trypanosomatids feature a multitude of unusual molecular features, including polycistronic transcription and subsequent processing by trans-splicing and polyadenylation. Regulation of protein coding genes is posttranscriptional and thus, translation regulation is fundamental for activating the developmental program of gene expression. The spliced-leader RNA is attached to all mRNAs. It contains an unusual hypermethylated cap-4 structure in its 5' end. The cap-binding complex, eIF4F, has gone through evolutionary changes in accordance with the requirement to bind cap-4. The eIF4F components in trypanosomatids are highly diverged from their orthologs in higher eukaryotes, and their potential functions are discussed. The cap-binding activity in all eukaryotes is a target for regulation and plays a similar role in trypanosomatids. Recent studies revealed a novel eIF4E-interacting protein, involved in directing stage-specific and stress-induced translation pathways. Translation regulation during stress also follows unusual regulatory cues, as the increased translation of Hsp83 following heat stress is driven by a defined element in the 3' UTR, unlike higher eukaryotes. Overall, the environmental switches experienced by trypanosomatids during their life cycle seem to affect their translational machinery in unique ways.
锥虫是古老的真核寄生虫，在昆虫媒介和哺乳动物宿主之间迁移，可导致人类和家畜患上一系列疾病。锥虫具有许多不同寻常的分子特征，包括多顺反子转录以及随后通过反式剪接和聚腺苷酸化进行的加工。蛋白质编码基因的调控发生在转录后，因此，翻译调控对于激活基因表达的发育程序至关重要。剪接前导RNA附着于所有mRNA。它在其5'端含有一个不寻常的高度甲基化的帽-4结构。帽结合复合物eIF4F已根据结合帽-4的需求经历了进化变化。锥虫中的eIF4F组分与其在高等真核生物中的直系同源物高度不同，并对其潜在功能进行了讨论。所有真核生物中的帽结合活性都是调控的靶点，在锥虫中发挥着类似的作用。最近的研究揭示了一种新型的与eIF4E相互作用的蛋白质，它参与指导阶段特异性和应激诱导的翻译途径。应激期间的翻译调控也遵循不同寻常的调控线索，因为热应激后Hsp83翻译的增加是由3'UTR中的一个特定元件驱动的，这与高等真核生物不同。总体而言，锥虫在其生命周期中经历的环境转换似乎以独特的方式影响其翻译机制。
