Foretek Dominika, Wu Jingyan, Hopper Anita K, Boguta Magdalena
Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland.
Department of Molecular Genetics, Center for RNA Biology, Ohio State University, Columbus, Ohio 43210, USA.
RNA. 2016 Mar;22(3):339-49. doi: 10.1261/rna.054973.115. Epub 2016 Jan 4.
tRNA is essential for translation and decoding of the proteome. The yeast proteome responds to stress and tRNA biosynthesis contributes in this response by repression of tRNA transcription and alterations of tRNA modification. Here we report that the stress response also involves processing of pre-tRNA 3' termini. By a combination of Northern analyses and RNA sequencing, we show that upon shift to elevated temperatures and/or to glycerol-containing medium, aberrant pre-tRNAs accumulate in yeast cells. For pre-tRNAUAU(Ile) and pre-tRNAUUU Lys) these aberrant forms are unprocessed at the 5' ends, but they possess extended 3' termini. Sequencing analyses showed that partial 3' processing precedes 5' processing for pre-tRNAUAU(Ile). An aberrant pre-tRNA(Tyr) that accumulates also possesses extended 3' termini, but it is processed at the 5' terminus. Similar forms of these aberrant pre-tRNAs are detected in the rex1Δ strain that is defective in 3' exonucleolytic trimming of pre-tRNAs but are absent in the lhp1Δ mutant lacking 3' end protection. We further show direct correlation between the inhibition of 3' end processing rate and the stringency of growth conditions. Moreover, under stress conditions Rex1 nuclease seems to be limiting for 3' end processing, by decreased availability linked to increased protection by Lhp1. Thus, our data document complex 3' processing that is inhibited by stress in a tRNA-type and condition-specific manner. This stress-responsive tRNA 3' end maturation process presumably contributes to fine-tune the levels of functional tRNA in budding yeast in response to environmental conditions.
转运RNA（tRNA）对于蛋白质组的翻译和解码至关重要。酵母蛋白质组对压力作出反应，tRNA生物合成通过抑制tRNA转录和改变tRNA修饰参与这一反应。在此我们报告，压力反应还涉及前体tRNA 3'末端的加工。通过Northern分析和RNA测序相结合的方法，我们发现，当转移到高温和/或含甘油的培养基中时，异常的前体tRNA在酵母细胞中积累。对于前体tRNAUAU（Ile）和前体tRNAUUU（Lys），这些异常形式在5'末端未被加工，但它们具有延长的3'末端。测序分析表明，前体tRNAUAU（Ile）的3'部分加工先于5'加工。积累的异常前体tRNA（Tyr）也具有延长的3'末端，但它在5'末端被加工。在对前体tRNA进行3'外切核酸修剪有缺陷的rex1Δ菌株中检测到这些异常前体tRNA的类似形式，但在缺乏3'末端保护的lhp1Δ突变体中不存在。我们进一步表明3'末端加工速率的抑制与生长条件的严格程度之间存在直接关联。此外，在压力条件下，Rex1核酸酶似乎因Lhp1增加保护导致可用性降低而限制了3'末端加工。因此，我们的数据证明了复杂的3'加工过程，该过程在tRNA类型和条件特异性的方式下受到压力抑制。这种应激反应性tRNA 3'末端成熟过程可能有助于在出芽酵母中根据环境条件微调功能性tRNA的水平。
