Arabidopsis Encodes Four tRNase Z Enzymes
Giusy CaninoEdyta BocianNicolas BarbezierManuel Echeverrı́aJoachim FornerStefan BinderAnita Marchfelder
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Functional transfer RNA (tRNA) molecules are a prerequisite for protein biosynthesis. Several processing steps are required to generate the mature functional tRNA from precursor molecules. Two of the early processing steps involve cleavage at the tRNA 5′ end and the tRNA 3′ end. While processing at the tRNA 5′ end is performed by RNase P, cleavage at the 3′ end is catalyzed by the endonuclease tRNase Z. In eukaryotes, tRNase Z enzymes are found in two versions: a short form of about 250 to 300 amino acids and a long form of about 700 to 900 amino acids. All eukaryotic genomes analyzed to date encode at least one long tRNase Z protein. Of those, Arabidopsis (Arabidopsis thaliana) is the only organism that encodes four tRNase Z proteins, two short forms and two long forms. We show here that the four proteins are distributed to different subcellular compartments in the plant cell: the nucleus, the cytoplasm, the mitochondrion, and the chloroplast. One tRNase Z is present only in the cytoplasm, one protein is found exclusively in mitochondria, while the third one has dual locations: nucleus and mitochondria. None of these three tRNase Z proteins is essential. The fourth tRNase Z protein is present in chloroplasts, and deletion of its gene results in an embryo-lethal phenotype. In vitro analysis with the recombinant proteins showed that all four tRNase Z enzymes have tRNA 3′ processing activity. In addition, the mitochondrial tRNase Z proteins cleave tRNA-like elements that serve as processing signals in mitochondrial mRNA maturation.Exoribonuclease
RNase PH
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Cleavage (geology)
Nuclease protection assay
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Aminoacylation
T arm
Polysome
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In cell-free protein-synthesizing systems containing an S30 extract from liver and brain cortex tissues of 22-day-old fetuses and of male WAG rats (1-900 days old), the minimal rate of protein synthesis was observed in the fetuses, while the maximal one - in 7-day-old animals. The difference in the rates of protein synthesis correlated with the minimal concentration of total tRNA in the former group and with its maximal concentration in the latter. In fetal tissues, an addition to cell-free systems of total tRNA isolated from homologous tissues of 7-day-old animals augmented protein synthesis up to a level observed in 7-day-old animals, whereas in the tissues of animals belonging to other age groups total tRNA had a far less pronounced stimulating effect which decreased with age. Fractionation of total tRNA and analysis of effects of individual tRNAs on protein synthesis demonstrated that the stimulating influence was induced by tRNA(2Arg), tRNA(4Arg) and tRNA(2Val) from brain cortex and by tRNA(2Leu), tRNA(5Leu), tRNA(2Val), tRNA(1Met) and tRNA(2Met) from liver.
Brain cortex
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Transfer RNA is an essential molecule for biological system, and each tRNA molecule commonly has a cloverleaf structure. Previously, we experimentally showed that some Drosophila tRNA (tRNA(Ala), tRNA(His), and tRNA(iMet)) molecules fit to form another, non-cloverleaf, structure in which the 3'-half of the tRNA molecules forms an alternative hairpin, and that the tRNA molecules are internally cleaved by the catalytic RNA of bacterial ribonuclease P (RNase P). Until now, the hyperprocessing reaction of tRNA has only been reported with Drosophila tRNAs. This time, we applied the hyperprocessing reaction to one of human tRNAs, human tyrosine tRNA, and we showed that this tRNA was also hyperprocessed by E. coli RNase P RNA. This tRNA is the first example for hyperprocessed non-Drosophila tRNAs. The results suggest that the hyperprocessing reaction can be a useful tool detect destablized tRNA molecules from any species.
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The phosphorothioate footprinting technique was applied to the investigation of phosphate moieties in tRNA substrates involved in interactions with M1 RNA, the catalytic subunit of Escherichia coli RNase P. In general agreement with previous data, all affected sites were localized in acceptor stem and T arm. But the analyzed examples for class I (Saccharomyces cerevisiae pre-tRNA(Phe) with short variable arm) and class II tRNAs (E. coli pre-tRNA(Tyr) with large variable arm) revealed substantial differences. In the complex with pre-tRNA(Phe), protection was observed at U55, C56, and G57, along the top of the T loop in the tertiary structure, whereas in pre-tRNA(Tyr), the protected positions were G57, A58, and A59, at the bottom of the T loop. These differences suggest that the size of the variable arm affects the spatial arrangement of the T arm, providing a possible explanation for the discrepancy in reports about the D arm requirement in truncated tRNA substrates for eukaryotic RNase P enzymes. Enhanced reactivities were found near the junction of acceptor and T stem (U6, 7, 8 in pre-tRNA(Phe) and G7, U63, U64 in pre-tRNA(Tyr)). This indicates a partial unfolding of the tRNA structure upon complex formation with RNase P RNA.
RNase PH
RNase MRP
T arm
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Cleavage (geology)
Nucleic acid structure
Fragmentation
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RNase MRP
RNase H
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在 Arabidopsis 的南船座基因在控制植物机关尺寸起一个关键作用。决定它的功能是在米饭的 ortholog，从米饭纸巾的通常认为的南船座 orthologous 基因被孤立并且指定了为 OsARGOS。这基因在米饭染色体有仅仅一个拷贝。OsARGOS 抄本在大多数米饭纸巾被检测，特别地在年轻纸巾，并且它的表示被植物生长素或细胞激动素的申请在米饭幼苗导致。表示 OsARGOS 的 Arabidopsis 植物导致了更大的机关，例如叶子和 siliques，与野类型的植物相比。有趣地，根生长也在这些转基因的 Arabidopsis 植物被提高。因此，转基因的植物的生物资源显著地被增加。进一步的分析揭示了那，与在 Arabidopsis 的 ARGOS 和像南船座的基因不同， OsARGOS 基因由房间数字和房间尺寸的增加扩大了机关。另外，抄本调整细胞分割或细胞生长的联系尺寸的基因在上面的几个器官铺平在转基因的 Arabidopsis 植物调整了。我们也转了到米饭的 OsARGOS 基因，而是转基因的植物没与控制植物相比在机关尺寸显示出任何变化。在机关尺寸控制的 OsARGOS 的功能在米饭取决于另外的尺寸管理者，是可能的。在 Arabidopsis 的 OsARGOS 的表达式可以激活在植物生长和开发的功课期间控制房间增长和房间扩大的发信号的小径。自从 OsARGOS 原因机关增大的表示，通过遗传工程的这基因的潜在的申请可以显著地在农业实践改进生物资源的生产。
Silique
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