Radío Santiago, Garat Beatriz, Sotelo-Silveira José, Smircich Pablo
Department of Genomics, Instituto de Investigaciones Biológicas Clemente Estable, Ministerio de Educación y Cultura, Montevideo, Uruguay.
Laboratory of Molecular Interactions, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.
Front Genet. 2020 Feb 28;11:166. doi: 10.3389/fgene.2020.00166. eCollection 2020.
It is generally accepted that the presence of ORFs in the 5' untranslated region of eukaryotic transcripts modulates the production of proteins by controlling the translation initiation rate of the main CDS. In trypanosomatid parasites, which almost exclusively depend on post-transcriptional mechanisms to regulate gene expression, translation has been identified as a key step. However, the mechanisms of control of translation are not fully understood. In the present work, we have annotated the 5'UTRs of the genome both in epimastigotes and metacyclic trypomastigotes and, using a stringent classification approach, we identified putative regulatory uORFs in about 9% of the analyzed 5'UTRs. The translation efficiency (TE) and translational levels of transcripts containing putative repressive uORFs were found to be significantly reduced. These findings are supported by the fact that proteomic methods only identify a low number of proteins coded by transcripts containing repressive uORF. We additionally show that AUG is the main translation initiator codon of repressive uORFs in . Interestingly, the decrease in TE is more pronounced when the uORFs overlaps the main CDS. In conclusion, we show that the presence of the uORF and features such as initiation codon and/or location of the uORFs may be acting to fine tune translation levels in these parasites.
一般认为，真核转录本5'非翻译区中开放阅读框（ORF）的存在通过控制主要编码区（CDS）的翻译起始速率来调节蛋白质的产生。在锥虫寄生虫中，其几乎完全依赖转录后机制来调节基因表达，翻译已被确定为关键步骤。然而，翻译的控制机制尚未完全了解。在本研究中，我们注释了无鞭毛体和循环后期锥鞭毛体基因组的5'非翻译区（UTR），并使用严格的分类方法，在约9%的分析5'UTR中鉴定出推定的调控上游开放阅读框（uORF）。发现含有推定抑制性uORF的转录本的翻译效率（TE）和翻译水平显著降低。蛋白质组学方法仅鉴定出少量由含有抑制性uORF的转录本编码的蛋白质，这一事实支持了这些发现。我们还表明，AUG是抑制性uORF的主要翻译起始密码子。有趣的是，当uORF与主要CDS重叠时，TE的降低更为明显。总之，我们表明uORF的存在以及起始密码子和/uORF位置等特征可能在微调这些寄生虫的翻译水平。
