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Hayne CK, Lewis TA, Stanley RE. Recent insights into the structure, function, and regulation of the eukaryotic transfer RNA splicing endonuclease complex. WILEY INTERDISCIPLINARY REVIEWS. RNA 2022; 13:e1717. [PMID: 35156311 PMCID: PMC9465713 DOI: 10.1002/wrna.1717] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 01/12/2022] [Accepted: 01/13/2022] [Indexed: 04/30/2023]
Abstract
The splicing of transfer RNA (tRNA) introns is a critical step of tRNA maturation, for intron-containing tRNAs. In eukaryotes, tRNA splicing is a multi-step process that relies on several RNA processing enzymes to facilitate intron removal and exon ligation. Splicing is initiated by the tRNA splicing endonuclease (TSEN) complex which catalyzes the excision of the intron through its two nuclease subunits. Mutations in all four subunits of the TSEN complex are linked to a family of neurodegenerative and neurodevelopmental diseases known as pontocerebellar hypoplasia (PCH). Recent studies provide molecular insights into the structure, function, and regulation of the eukaryotic TSEN complex and are beginning to illuminate how mutations in the TSEN complex lead to neurodegenerative disease. Using new advancements in the prediction of protein structure, we created a three-dimensional model of the human TSEN complex. We review functions of the TSEN complex beyond tRNA splicing by highlighting recently identified substrates of the eukaryotic TSEN complex and discuss mechanisms for the regulation of tRNA splicing, by enzymes that modify cleaved tRNA exons and introns. Finally, we review recent biochemical and animal models that have worked to address the mechanisms that drive PCH and synthesize these studies with previous studies to try to better understand PCH pathogenesis. This article is categorized under: RNA Processing > tRNA Processing RNA in Disease and Development > RNA in Disease RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition.
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Affiliation(s)
- Cassandra K Hayne
- Department of Health and Human Services, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA
| | - Tanae A Lewis
- Department of Chemistry, North Carolina Agricultural and Technical State University, Greensboro, North Carolina, USA
| | - Robin E Stanley
- Department of Health and Human Services, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA
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2
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Structural Basis for tRNA Mimicry by a Bacterial Y RNA. Structure 2018; 26:1635-1644.e3. [PMID: 30318468 DOI: 10.1016/j.str.2018.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 07/03/2018] [Accepted: 09/10/2018] [Indexed: 12/29/2022]
Abstract
Noncoding Y RNAs are present in both animal cells and many bacteria. In all species examined, Y RNAs tether the Ro60 protein to an effector protein to perform various cellular functions. Recently, a new Y RNA subfamily was identified in bacteria. Bioinformatic analyses of these YrlA (Y RNA-like A) RNAs predict that the effector-binding domain resembles tRNA. We present the structure of this domain, the overall folding of which is strikingly similar to canonical tRNAs. The tertiary interactions that are responsible for stabilizing tRNA are present in YrlA, making it a close tRNA mimic. However, YrlA lacks a free CCA end and contains a kink in the stem corresponding to the anticodon stem. Since nucleotides in the D and T stems are conserved among YrlAs, they may be an interaction site for an unknown factor. Our experiments identify YrlA RNAs as a new class of tRNA mimics.
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3
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Kaneta A, Fujishima K, Morikazu W, Hori H, Hirata A. The RNA-splicing endonuclease from the euryarchaeaon Methanopyrus kandleri is a heterotetramer with constrained substrate specificity. Nucleic Acids Res 2018; 46:1958-1972. [PMID: 29346615 PMCID: PMC5829648 DOI: 10.1093/nar/gky003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 12/25/2017] [Accepted: 01/03/2018] [Indexed: 11/14/2022] Open
Abstract
Four different types (α4, α'2, (αβ)2 and ϵ2) of RNA-splicing endonucleases (EndAs) for RNA processing are known to exist in the Archaea. Only the (αβ)2 and ϵ2 types can cleave non-canonical introns in precursor (pre)-tRNA. Both enzyme types possess an insert associated with a specific loop, allowing broad substrate specificity in the catalytic α units. Here, the hyperthermophilic euryarchaeon Methanopyrus kandleri (MKA) was predicted to harbor an (αβ)2-type EndA lacking the specific loop. To characterize MKA EndA enzymatic activity, we constructed a fusion protein derived from MKA α and β subunits (fMKA EndA). In vitro assessment demonstrated complete removal of the canonical bulge-helix-bulge (BHB) intron structure from MKA pre-tRNAAsn. However, removal of the relaxed BHB structure in MKA pre-tRNAGlu was inefficient compared to crenarchaeal (αβ)2 EndA, and the ability to process the relaxed intron within mini-helix RNA was not detected. fMKA EndA X-ray structure revealed a shape similar to that of other EndA types, with no specific loop. Mapping of EndA types and their specific loops and the tRNA gene diversity among various Archaea suggest that MKA EndA is evolutionarily related to other (αβ)2-type EndAs found in the Thaumarchaeota, Crenarchaeota and Aigarchaeota but uniquely represents constrained substrate specificity.
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Affiliation(s)
- Ayano Kaneta
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Kosuke Fujishima
- Earth-Life Science Institute, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan
| | - Wataru Morikazu
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Hiroyuki Hori
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Akira Hirata
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
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Mohanta TK, Syed AS, Ameen F, Bae H. Novel Genomic and Evolutionary Perspective of Cyanobacterial tRNAs. Front Genet 2017; 8:200. [PMID: 29321793 PMCID: PMC5733544 DOI: 10.3389/fgene.2017.00200] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 11/21/2017] [Indexed: 11/30/2022] Open
Abstract
Transfer RNA (tRNA) plays a central role in protein synthesis and acts as an adaptor molecule between an mRNA and an amino acid. A tRNA has an L-shaped clover leaf-like structure and contains an acceptor arm, D-arm, D-loop, anti-codon arm, anti-codon loop, variable loop, Ψ-arm and Ψ-loop. All of these arms and loops are important in protein translation. Here, we aimed to delineate the genomic architecture of these arms and loops in cyanobacterial tRNA. Studies from tRNA sequences from 61 cyanobacterial species showed that, except for few tRNAs (tRNAAsn, tRNALeu, tRNAGln, and tRNAMet), all contained a G nucleotide at the 1st position in the acceptor arm. tRNALeu and tRNAMet did not contain any conserved nucleotides at the 1st position whereas tRNAAsn and tRNAGln contained a conserved U1 nucleotide. In several tRNA families, the variable region also contained conserved nucleotides. Except for tRNAMet and tRNAGlu, all other tRNAs contained a conserved A nucleotide at the 1st position in the D-loop. The Ψ-loop contained a conserved U1-U2-C3-x-A5-x-U7 sequence, except for tRNAGly, tRNAAla, tRNAVal, tRNAPhe, tRNAThr, and tRNAGln in which the U7 nucleotide was not conserved. However, in tRNAAsp, the U7 nucleotide was substituted with a C7 nucleotide. Additionally, tRNAArg, tRNAGly, and tRNALys of cyanobacteria contained a group I intron within the anti-codon loop region. Maximum composite likelihood study on the transition/transversion of cyanobacterial tRNA revealed that the rate of transition was higher than the rate of transversion. An evolutionary tree was constructed to understand the evolution of cyanobacterial tRNA and analyses revealed that cyanobacterial tRNA may have evolved polyphyletically with high rate of gene loss.
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Affiliation(s)
- Tapan K Mohanta
- School of Biotechnology, Yeungnam University, Gyeongsan, South Korea
| | - Asad S Syed
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Fuad Ameen
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Hanhong Bae
- School of Biotechnology, Yeungnam University, Gyeongsan, South Korea
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Smith DR, Keeling PJ. Protists and the Wild, Wild West of Gene Expression: New Frontiers, Lawlessness, and Misfits. Annu Rev Microbiol 2016; 70:161-78. [PMID: 27359218 DOI: 10.1146/annurev-micro-102215-095448] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The DNA double helix has been called one of life's most elegant structures, largely because of its universality, simplicity, and symmetry. The expression of information encoded within DNA, however, can be far from simple or symmetric and is sometimes surprisingly variable, convoluted, and wantonly inefficient. Although exceptions to the rules exist in certain model systems, the true extent to which life has stretched the limits of gene expression is made clear by nonmodel systems, particularly protists (microbial eukaryotes). The nuclear and organelle genomes of protists are subject to the most tangled forms of gene expression yet identified. The complicated and extravagant picture of the underlying genetics of eukaryotic microbial life changes how we think about the flow of genetic information and the evolutionary processes shaping it. Here, we discuss the origins, diversity, and growing interest in noncanonical protist gene expression and its relationship to genomic architecture.
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Affiliation(s)
- David Roy Smith
- Department of Biology, University of Western Ontario, London, Ontario, Canada N6A 5B7;
| | - Patrick J Keeling
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4;
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Shapiro JA. Nothing in Evolution Makes Sense Except in the Light of Genomics: Read-Write Genome Evolution as an Active Biological Process. BIOLOGY 2016; 5:E27. [PMID: 27338490 PMCID: PMC4929541 DOI: 10.3390/biology5020027] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 05/20/2016] [Accepted: 06/02/2016] [Indexed: 01/15/2023]
Abstract
The 21st century genomics-based analysis of evolutionary variation reveals a number of novel features impossible to predict when Dobzhansky and other evolutionary biologists formulated the neo-Darwinian Modern Synthesis in the middle of the last century. These include three distinct realms of cell evolution; symbiogenetic fusions forming eukaryotic cells with multiple genome compartments; horizontal organelle, virus and DNA transfers; functional organization of proteins as systems of interacting domains subject to rapid evolution by exon shuffling and exonization; distributed genome networks integrated by mobile repetitive regulatory signals; and regulation of multicellular development by non-coding lncRNAs containing repetitive sequence components. Rather than single gene traits, all phenotypes involve coordinated activity by multiple interacting cell molecules. Genomes contain abundant and functional repetitive components in addition to the unique coding sequences envisaged in the early days of molecular biology. Combinatorial coding, plus the biochemical abilities cells possess to rearrange DNA molecules, constitute a powerful toolbox for adaptive genome rewriting. That is, cells possess "Read-Write Genomes" they alter by numerous biochemical processes capable of rapidly restructuring cellular DNA molecules. Rather than viewing genome evolution as a series of accidental modifications, we can now study it as a complex biological process of active self-modification.
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Affiliation(s)
- James A Shapiro
- Department of Biochemistry and Molecular Biology, University of Chicago, GCIS W123B, 979 E. 57th Street, Chicago, IL 60637, USA.
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Hirose Y, Ikeda KT, Noro E, Hiraoka K, Tomita M, Kanai A. Precise mapping and dynamics of tRNA-derived fragments (tRFs) in the development of Triops cancriformis (tadpole shrimp). BMC Genet 2015; 16:83. [PMID: 26168920 PMCID: PMC4501094 DOI: 10.1186/s12863-015-0245-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 06/30/2015] [Indexed: 12/03/2022] Open
Abstract
Background In a deep sequencing analysis of small RNAs prepared from a living fossil, the tadpole shrimp Triops cancriformis, a 32-nt small RNA was specifically detected in the adult stage. A nucleotide sequence comparison between the 32-nt small RNA and predicted tRNA sequences in the draft nuclear genomic DNA showed that the small RNA was derived from tRNAGly(GCC). To determine the overall features of the tRNA-derived fragments (tRFs) of T. cancriformis, the small RNA sequences in each of the six developmental stages (egg, 1st − 4th instar larvae, and adult) were compared with the mitochondrial and nuclear tRNA sequences. Results We found that the tRFs were derived from mitochondrial and nuclear tRNAs corresponding to 16 and 39 anticodons, respectively. The total read number of nuclear tRFs was approximately 400 times larger than the number of mitochondrial tRFs. Interestingly, the main regions in each parental tRNA from which these tRFs were derived differed, depending on the parental anticodon. Mitochondrial tRFSer(GCU)s were abundantly produced from the 5’ half regions of the parental tRNA, whereas mitochondrial tRFVal(UAC)s were mainly produced from the 3’ end regions. Highly abundant nuclear tRFs, tRFGly(GCC)s, tRFGly(CCC)s, tRFGlu(CUC)s, and tRFLys(CUU)s were derived from the 5’ half regions of the parental tRNAs. Further analysis of the tRF read counts in the individual developmental stages suggested that the expression of mitochondrial and nuclear tRFs differed during the six stages. Based on these data, we precisely summarized the positions of the tRFs in their parental tRNAs and their expression changes during development. Conclusions Our results reveal the entire dynamics of the tRFs from both the nuclear and mitochondrial genomes of T. cancriformis and indicate that the majority of tRFs in the cell are derived from nuclear tRNAs. This study provides the first examples of developmentally expressed mitochondrial tRFs. Electronic supplementary material The online version of this article (doi:10.1186/s12863-015-0245-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yuka Hirose
- Institute for Advanced Biosciences, Keio University, Tsuruoka, 997-0017, Japan. .,Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, 252-8520, Japan.
| | - Kahori T Ikeda
- Institute for Advanced Biosciences, Keio University, Tsuruoka, 997-0017, Japan. .,Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, 252-8520, Japan.
| | - Emiko Noro
- Institute for Advanced Biosciences, Keio University, Tsuruoka, 997-0017, Japan.
| | - Kiriko Hiraoka
- Institute for Advanced Biosciences, Keio University, Tsuruoka, 997-0017, Japan.
| | - Masaru Tomita
- Institute for Advanced Biosciences, Keio University, Tsuruoka, 997-0017, Japan. .,Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, 252-8520, Japan. .,Faculty of Environment and Information Studies, Keio University, Fujisawa, 252-0882, Japan.
| | - Akio Kanai
- Institute for Advanced Biosciences, Keio University, Tsuruoka, 997-0017, Japan. .,Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, 252-8520, Japan. .,Faculty of Environment and Information Studies, Keio University, Fujisawa, 252-0882, Japan.
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8
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Suzuki S, Shirato S, Hirakawa Y, Ishida KI. Nucleomorph Genome Sequences of Two Chlorarachniophytes, Amorphochlora amoebiformis and Lotharella vacuolata. Genome Biol Evol 2015; 7:1533-45. [PMID: 26002880 PMCID: PMC4494063 DOI: 10.1093/gbe/evv096] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Many algal groups acquired complex plastids by the uptake of green and red algae through multiple secondary endosymbioses. As a result of gene loss and transfer during the endosymbiotic processes, algal endosymbiont nuclei disappeared in most cases. However, chlorarachniophytes and cryptophytes still possess a relict nucleus, so-called the nucleomorph, of the green and red algal endosymbiont, respectively. Nucleomorph genomes are an interesting and suitable model to study the reductive evolution of endosymbiotically derived genomes. To date, nucleomorph genomes have been sequenced in four cryptophyte species and two chlorarachniophyte species, including Bigelowiella natans (373 kb) and Lotharella oceanica (610 kb). In this study, we report complete nucleomorph genome sequences of two chlorarachniophytes, Amorphochlora amoebiformis and Lotharella vacuolata, to gain insight into the reductive evolution of nucleomorph genomes in the chlorarachniophytes. The nucleomorph genomes consist of three chromosomes totaling 374 and 432 kb in size in A. amoebiformis and L. vacuolata, respectively. Comparative analyses among four chlorarachniophyte nucleomorph genomes revealed that these sequences share 171 function-predicted genes (86% of total 198 function-predicted nucleomorph genes), including the same set of genes encoding 17 plastid-associated proteins, and no evidence of a recent nucleomorph-to-nucleus gene transfer was found. This suggests that chlorarachniophyte nucleomorph genomes underwent most of their reductive evolution prior to the radiation of extent members of the group. However, there are slight variations in genome size, GC content, duplicated gene number, and subtelomeric regions among the four nucleomorph genomes, suggesting that the genomes might be undergoing changes that do not affect the core functions in each species.
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Affiliation(s)
- Shigekatsu Suzuki
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Shu Shirato
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Yoshihisa Hirakawa
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Ken-Ichiro Ishida
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
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Abstract
tRNAs are widely believed to segregate into two classes, I and II. Computational analysis of eukaryotic tRNA entries in Genomic tRNA Database, however, leads to new, albeit paradoxical, presence of more than a thousand class-I tRNAs with uncharacteristic long variable arms (V-arms), like in class-II. Out of 62,202 tRNAs from 69 eukaryotes, as many as 1431 class-I tRNAs have these novel extended V-arms, and we refer to them as paradoxical tRNAs (pxtRNAs). A great majority of these 1431 pxtRNA genes are located in intergenic regions, about 18% embedded in introns of genes or ESTs, and just one in 3'UTR. A check on the conservations of 2D and 3D base pairs for each position of these pxtRNAs reveals a few variations, but they seem to have almost all the known features (already known identity and conserved elements of tRNA). Analyses of the A-Box and B-Box of these pxtRNA genes in eukaryotes display salient deviations from the previously annotated conserved features of the standard promoters, whereas the transcription termination signals are just canonical and non-canonical runs of thymidine, similar to the ones in standard tRNA genes. There is just one such pxtRNA(ProAGG) gene in the entire human genome, and the availability of data allows epigenetic analysis of this human pxtRNA(ProAGG) in three different cell lines, H1 hESC, K562, and NHEK, to assess the level of its expression. Histone acetylation and methylation of this lone pxtRNA(ProAGG) gene in human differ from that of the nine standard human tRNA(ProAGG) genes. The V-arm nucleotide sequences and their secondary structures in pxtRNA differ from that of class-II tRNA. Considering these differences, hypotheses of alternative splicing, non-canonical intron and gene transfer are examined to partially improve the Cove scores of these pxtRNAs and to critically question their antecedence and novelty.
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Affiliation(s)
- Sanga Mitra
- a Computational Biology Group , Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700032 , India
| | - Arpa Samadder
- a Computational Biology Group , Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700032 , India
| | - Pijush Das
- b Cancer Biology & Inflammatory Disorder Division , Indian Institute of Chemical Biology , Kolkata , India
| | - Smarajit Das
- c Department of Medical Biochemistry and Cell Biology , Institute of Biomedicine, University of Gothenburg , Gothenburg , Sweden
| | - Jayprokas Chakrabarti
- a Computational Biology Group , Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700032 , India.,d Gyanxet, BF 286 Salt Lake, Kolkata , India
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Disrupted tRNA Genes and tRNA Fragments: A Perspective on tRNA Gene Evolution. Life (Basel) 2015; 5:321-31. [PMID: 25629271 PMCID: PMC4390854 DOI: 10.3390/life5010321] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 01/14/2015] [Accepted: 01/21/2015] [Indexed: 01/17/2023] Open
Abstract
Transfer RNAs (tRNAs) are small non-coding RNAs with lengths of approximately 70-100 nt. They are directly involved in protein synthesis by carrying amino acids to the ribosome. In this sense, tRNAs are key molecules that connect the RNA world and the protein world. Thus, study of the evolution of tRNA molecules may reveal the processes that led to the establishment of the central dogma: genetic information flows from DNA to RNA to protein. Thanks to the development of DNA sequencers in this century, we have determined a huge number of nucleotide sequences from complete genomes as well as from transcriptomes in many species. Recent analyses of these large data sets have shown that particular tRNA genes, especially in Archaea, are disrupted in unique ways: some tRNA genes contain multiple introns and some are split genes. Even tRNA molecules themselves are fragmented post-transcriptionally in many species. These fragmented small RNAs are known as tRNA-derived fragments (tRFs). In this review, I summarize the progress of research into the disrupted tRNA genes and the tRFs, and propose a possible model for the molecular evolution of tRNAs based on the concept of the combination of fragmented tRNA halves.
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Mitra S, Das P, Samadder A, Das S, Betai R, Chakrabarti J. Eukaryotic tRNAs fingerprint invertebrates vis-à-vis vertebrates. J Biomol Struct Dyn 2015; 33:2104-20. [PMID: 25581620 DOI: 10.1080/07391102.2014.990925] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
During translation, aminoacyl-tRNA synthetases recognize the identities of the tRNAs to charge them with their respective amino acids. The conserved identities of 58,244 eukaryotic tRNAs of 24 invertebrates and 45 vertebrates in genomic tRNA database were analyzed and their novel features extracted. The internal promoter sequences, namely, A-Box and B-Box, were investigated and evidence gathered that the intervention of optional nucleotides at 17a and 17b correlated with the optimal length of the A-Box. The presence of canonical transcription terminator sequences at the immediate vicinity of tRNA genes was ventured. Even though non-canonical introns had been reported in red alga, green alga, and nucleomorph so far, fairly motivating evidence of their existence emerged in tRNA genes of other eukaryotes. Non-canonical introns were seen to interfere with the internal promoters in two cases, questioning their transcription fidelity. In a first of its kind, phylogenetic constructs based on tRNA molecules delineated and built the trees of the vast and diverse invertebrates and vertebrates. Finally, two tRNA models representing the invertebrates and the vertebrates were drawn, by isolating the dominant consensus in the positional fluctuations of nucleotide compositions.
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Affiliation(s)
- Sanga Mitra
- a Computational Biology Group , Indian Association for the Cultivation of Science , Kolkata 700032 , India
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12
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Yoshihisa T. Handling tRNA introns, archaeal way and eukaryotic way. Front Genet 2014; 5:213. [PMID: 25071838 PMCID: PMC4090602 DOI: 10.3389/fgene.2014.00213] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Accepted: 06/20/2014] [Indexed: 11/25/2022] Open
Abstract
Introns are found in various tRNA genes in all the three kingdoms of life. Especially, archaeal and eukaryotic genomes are good sources of tRNA introns that are removed by proteinaceous splicing machinery. Most intron-containing tRNA genes both in archaea and eukaryotes possess an intron at a so-called canonical position, one nucleotide 3′ to their anticodon, while recent bioinformatics have revealed unusual types of tRNA introns and their derivatives especially in archaeal genomes. Gain and loss of tRNA introns during various stages of evolution are obvious both in archaea and eukaryotes from analyses of comparative genomics. The splicing of tRNA molecules has been studied extensively from biochemical and cell biological points of view, and such analyses of eukaryotic systems provided interesting findings in the past years. Here, I summarize recent progresses in the analyses of tRNA introns and the splicing process, and try to clarify new and old questions to be solved in the next stages.
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Affiliation(s)
- Tohru Yoshihisa
- Graduate School of Life Science, University of Hyogo Ako-gun, Hyogo, Japan
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13
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Fujishima K, Kanai A. tRNA gene diversity in the three domains of life. Front Genet 2014; 5:142. [PMID: 24904642 PMCID: PMC4033280 DOI: 10.3389/fgene.2014.00142] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 04/28/2014] [Indexed: 11/29/2022] Open
Abstract
Transfer RNA (tRNA) is widely known for its key role in decoding mRNA into protein. Despite their necessity and relatively short nucleotide sequences, a large diversity of gene structures and RNA secondary structures of pre-tRNAs and mature tRNAs have recently been discovered in the three domains of life. Growing evidences of disrupted tRNA genes in the genomes of Archaea reveals unique gene structures such as, intron-containing tRNA, split tRNA, and permuted tRNA. Coding sequence for these tRNAs are either separated with introns, fragmented, or permuted at the genome level. Although evolutionary scenario behind the tRNA gene disruption is still unclear, diversity of tRNA structure seems to be co-evolved with their processing enzyme, so-called RNA splicing endonuclease. Metazoan mitochondrial tRNAs (mtRNAs) are known for their unique lack of either one or two arms from the typical tRNA cloverleaf structure, while still maintaining functionality. Recently identified nematode-specific V-arm containing tRNAs (nev-tRNAs) possess long variable arms that are specific to eukaryotic class II tRNASer and tRNALeu but also decode class I tRNA codons. Moreover, many tRNA-like sequences have been found in the genomes of different organisms and viruses. Thus, this review is aimed to cover the latest knowledge on tRNA gene diversity and further recapitulate the evolutionary and biological aspects that caused such uniqueness.
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Affiliation(s)
- Kosuke Fujishima
- NASA Ames Research Center Moffett Field, CA, USA ; Institute for Advanced Biosciences, Keio University Tsuruoka, Japan
| | - Akio Kanai
- Institute for Advanced Biosciences, Keio University Tsuruoka, Japan
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14
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Soma A. Circularly permuted tRNA genes: their expression and implications for their physiological relevance and development. Front Genet 2014; 5:63. [PMID: 24744771 PMCID: PMC3978253 DOI: 10.3389/fgene.2014.00063] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 03/12/2014] [Indexed: 12/02/2022] Open
Abstract
A number of genome analyses and searches using programs that focus on the RNA-specific bulge-helix-bulge (BHB) motif have uncovered a wide variety of disrupted tRNA genes. The results of these analyses have shown that genetic information encoding functional RNAs is described in the genome cryptically and is retrieved using various strategies. One such strategy is represented by circularly permuted tRNA genes, in which the sequences encoding the 5′-half and 3′-half of the specific tRNA are separated and inverted on the genome. Biochemical analyses have defined a processing pathway in which the termini of tRNA precursors (pre-tRNAs) are ligated to form a characteristic circular RNA intermediate, which is then cleaved at the acceptor-stem to generate the typical cloverleaf structure with functional termini. The sequences adjacent to the processing site located between the 3′-half and the 5′-half of pre-tRNAs potentially form a BHB motif, which is the dominant recognition site for the tRNA-intron splicing endonuclease, suggesting that circularization of pre-tRNAs depends on the splicing machinery. Some permuted tRNAs contain a BHB-mediated intron in their 5′- or 3′-half, meaning that removal of an intron, as well as swapping of the 5′- and 3′-halves, are required during maturation of their pre-tRNAs. To date, 34 permuted tRNA genes have been identified from six species of unicellular algae and one archaeon. Although their physiological significance and mechanism of development remain unclear, the splicing system of BHB motifs seems to have played a key role in the formation of permuted tRNA genes. In this review, current knowledge of circularly permuted tRNA genes is presented and some unanswered questions regarding these species are discussed.
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Affiliation(s)
- Akiko Soma
- Graduate School of Horticulture, Chiba University Matsudo, Japan
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15
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Soma A, Sugahara J, Onodera A, Yachie N, Kanai A, Watanabe S, Yoshikawa H, Ohnuma M, Kuroiwa H, Kuroiwa T, Sekine Y. Identification of highly-disrupted tRNA genes in nuclear genome of the red alga, Cyanidioschyzon merolae 10D. Sci Rep 2014; 3:2321. [PMID: 23900518 PMCID: PMC3728597 DOI: 10.1038/srep02321] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 07/10/2013] [Indexed: 12/03/2022] Open
Abstract
The limited locations of tRNA introns are crucial for eukaryal tRNA-splicing endonuclease recognition. However, our analysis of the nuclear genome of an early-diverged red alga, Cyanidioschyzon merolae, demonstrated the first evidence of nuclear-encoded tRNA genes that contain ectopic and/or multiple introns. Some genes exhibited both intronic and permuted structures in which the 3′-half of the tRNA coding sequence lies upstream of the 5′-half, and an intron is inserted into either half. These highly disrupted tRNA genes, which account for 63% of all nuclear tRNA genes, are expressed via the orderly and sequential processing of bulge-helix-bulge (BHB) motifs at intron-exon junctions and termini of permuted tRNA precursors, probably by a C. merolae tRNA-splicing endonuclease with an unidentified subunit architecture. The results revealed a considerable diversity in eukaryal tRNA intron properties and endonuclease architectures, which will help to elucidate the acquisition mechanism of the BHB-mediated disrupted tRNA genes.
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Affiliation(s)
- Akiko Soma
- Department of Life Science, College of Science, Rikkyo University, Toshima, Tokyo 171-8501, Japan
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Abstract
Many RNA families, i.e., groups of homologous RNA genes, belong to RNA classes, such as tRNAs, snoRNAs, or microRNAs, that are characterized by common sequence motifs and/or common secondary structure features. The detection of new members of RNA classes, as well as the comprehensive annotation of genomes with members of RNA classes is a challenging task that goes beyond simple homology search. Computational methods addressing this problem typically use a three-tiered approach: In the first step an efficient and sensitive filter is employed. In the second step the candidate set is narrowed down using computationally expensive methods geared towards specificity. In the final step the hits are annotated with class-specific features and scored. Here we review the tools that are currently available for a diverse set of RNA classes.
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Michely S, Toulza E, Subirana L, John U, Cognat V, Maréchal-Drouard L, Grimsley N, Moreau H, Piganeau G. Evolution of codon usage in the smallest photosynthetic eukaryotes and their giant viruses. Genome Biol Evol 2013; 5:848-59. [PMID: 23563969 PMCID: PMC3673656 DOI: 10.1093/gbe/evt053] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Prasinoviruses are among the largest viruses (>200 kb) and encode several hundreds of
protein coding genes, including most genes of the DNA replication machinery and several
genes involved in transcription and translation, as well as transfer RNAs (tRNAs). They
can infect and lyse small eukaryotic planktonic marine green algae, thereby affecting
global algal population dynamics. Here, we investigate the causes of codon usage bias
(CUB) in one prasinovirus, OtV5, and its host Ostreococcus tauri, during
a viral infection using microarray expression data. We show that 1) CUB in the host and in
the viral genes increases with expression levels and 2) optimal codons use those tRNAs
encoded by the most abundant host tRNA genes, supporting the notion of translational
optimization by natural selection. We find evidence that viral tRNA genes complement the
host tRNA pool for those viral amino acids whose host tRNAs are in short supply. We
further discuss the coevolution of CUB in hosts and prasinoviruses by comparing optimal
codons in three evolutionary diverged host–virus-specific pairs whose complete
genome sequences are known.
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Affiliation(s)
- Stephanie Michely
- UPMC Univ Paris 06, UMR7232, BIOM, Observatoire Océanologique, F-66650, Banyuls-sur-Mer, France
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Avatar pre-tRNAs help elucidate the properties of tRNA-splicing endonucleases that produce tRNA from permuted genes. Proc Natl Acad Sci U S A 2012; 109:21325-9. [PMID: 23236183 DOI: 10.1073/pnas.1219336110] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Unusual tRNA genes, found in some algae, have their mature terminal 3' portion in front of their 5' portion in the genome. The transcripts from such genes must be cleaved by a pre-tRNA endonuclease to form a functional tRNA. We present a mechanism for the generation of "corrected" tRNAs from such a "permuted" pre-tRNA configuration. We used two avatar (av) or model pre-tRNAs and two splicing endonucleases with distinct mechanisms of recognition of the pre-tRNA. The splicing results are compatible with an evolutionary route in which permuted genes result from a duplication event followed by DNA rearrangement. The model pre-tRNAs permit description of the features that a transcript, derived from a rearranged duplicated gene, must have to give rise to functional tRNA. The two tRNA endonucleases are a eukaryal enzyme that normally acts in a mature domain-dependent mode and an archaeal enzyme that acts in a mature domain-independent mode. Both av pre-tRNAs are able to fold into two conformations: 1 and 2. We find that only conformation 2 can yield a corrected functional tRNA. This result is consistent with contemporary algae representing snapshots of different evolutionary stages, with duplicated genes preceding recombinatorial events generating a permutated gene. In a scenario elucidated by the use of the av pre-tRNAs, algal permuted tRNA genes could have further lost one of two mature domains, eliminating steric problems for the algal tRNA endonuclease, which remains a typical eukaryal enzyme capable of correcting the permuted transcript to a functional tRNA.
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Szenes A, Pál G. Mapping hidden potential identity elements by computing the average discriminating power of individual tRNA positions. DNA Res 2012; 19:245-58. [PMID: 22378766 PMCID: PMC3372374 DOI: 10.1093/dnares/dss008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The recently published discrete mathematical method, extended consensus partition (ECP), identifies nucleotide types at each position that are strictly absent from a given sequence set, while occur in other sets. These are defined as discriminating elements (DEs). In this study using the ECP approach, we mapped potential hidden identity elements that discriminate the 20 different tRNA identities. We filtered the tDNA data set for the obligatory presence of well-established tRNA features, and then separately for each identity set, the presence of already experimentally identified strictly present identity elements. The analysis was performed on the three kingdoms of life. We determined the number of DE, e.g. the number of sets discriminated by the given position, for each tRNA position of each tRNA identity set. Then, from the positional DE numbers obtained from the 380 pairwise comparisons of the 20 identity sets, we calculated the average excluding value (AEV) for each tRNA position. The AEV provides a measure on the overall discriminating power of each position. Using a statistical analysis, we show that positional AEVs correlate with the number of already identified identity elements. Positions having high AEV but lacking published identity elements predict hitherto undiscovered tRNA identity elements.
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Affiliation(s)
- Aron Szenes
- Department of Biochemistry, Eötvös University, Budapest, Hungary
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20
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Moreira S, Breton S, Burger G. Unscrambling genetic information at the RNA level. WILEY INTERDISCIPLINARY REVIEWS-RNA 2012; 3:213-28. [PMID: 22275292 DOI: 10.1002/wrna.1106] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Genomics aims at unraveling the blueprint of life; however, DNA sequence alone does not always reveal the proteins and structural RNAs encoded by the genome. The reason is that genetic information is often encrypted. Recognizing the logic of encryption, and understanding how living cells decode hidden information--at the level of DNA, RNA or protein--is challenging. RNA-level decryption includes topical RNA editing and more 'macroscopic' transcript rearrangements. The latter events involve the four types of introns recognized to date, notably spliceosomal, group I, group II, and archaeal/tRNA splicing. Intricate variants, such as alternative splicing and trans-splicing, have been reported for each intron type, but the biological significance has not always been confirmed. Novel RNA-level unscrambling processes were recently discovered in mitochondria of dinoflagellates and diplonemids, and potentially euglenids. These processes seem not to rely on known introns, and the corresponding molecular mechanisms remain to be elucidated.
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Affiliation(s)
- Sandrine Moreira
- Robert-Cedergren Centre for Bioinformatics and Genomics, Department of Biochemistry, Université de Montréal, Montreal, Quebec, Canada
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Hamashima K, Fujishima K, Masuda T, Sugahara J, Tomita M, Kanai A. Nematode-specific tRNAs that decode an alternative genetic code for leucine. Nucleic Acids Res 2011; 40:3653-62. [PMID: 22187151 PMCID: PMC3333845 DOI: 10.1093/nar/gkr1226] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Class II transfer RNAs (tRNAs), including tRNALeu and tRNASer, have an additional stem and loop structure, the long variable arm (V-arm). Here, we describe Class II tRNAs with a unique anticodon corresponding to neither leucine nor serine. Because these tRNAs are specifically conserved among the nematodes, we have called them ‘nematode-specific V-arm-containing tRNAs’ (nev-tRNAs). The expression of nev-tRNA genes in Caenorhabditis elegans was confirmed experimentally. A comparative sequence analysis suggested that the nev-tRNAs derived phylogenetically from tRNALeu. In vitro aminoacylation assays showed that nev-tRNAGly and nev-tRNAIle are only charged with leucine, which is inconsistent with their anticodons. Furthermore, the deletion and mutation of crucial determinants for leucylation in nev-tRNA led to a marked loss of activity. An in vitro translation analysis showed that nev-tRNAGly decodes GGG as leucine instead of the universal glycine code, indicating that nev-tRNAs can be incorporated into ribosomes and participate in protein biosynthesis. Our findings provide the first example of unexpected tRNAs that do not consistently obey the general translation rules for higher eukaryotes.
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Affiliation(s)
- Kiyofumi Hamashima
- Institute for Advanced Biosciences, Keio University, Tsuruoka 997-0017, Japan
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22
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Lai LB, Bernal-Bayard P, Mohannath G, Lai SM, Gopalan V, Vioque A. A functional RNase P protein subunit of bacterial origin in some eukaryotes. Mol Genet Genomics 2011; 286:359-69. [PMID: 21987179 DOI: 10.1007/s00438-011-0651-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 09/23/2011] [Indexed: 11/27/2022]
Abstract
RNase P catalyzes 5'-maturation of tRNAs. While bacterial RNase P comprises an RNA catalyst and a protein cofactor, the eukaryotic (nuclear) variant contains an RNA and up to ten proteins, all unrelated to the bacterial protein. Unexpectedly, a nuclear-encoded bacterial RNase P protein (RPP) homolog is found in several prasinophyte algae including Ostreococcus tauri. We demonstrate that recombinant O. tauri RPP can functionally reconstitute with bacterial RNase P RNAs (RPRs) but not with O. tauri organellar RPRs, despite the latter's presumed bacterial origins. We also show that O. tauri PRORP, a homolog of Arabidopsis PRORP-1, displays tRNA 5'-processing activity in vitro. We discuss the implications of the striking diversity of RNase P in O. tauri, the smallest known free-living eukaryote.
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Affiliation(s)
- Lien B Lai
- Department of Biochemistry, The Ohio State University, Columbus, OH 43210, USA
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23
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Su AAH, Randau L. A-to-I and C-to-U editing within transfer RNAs. BIOCHEMISTRY (MOSCOW) 2011; 76:932-7. [DOI: 10.1134/s0006297911080098] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Chan PP, Cozen AE, Lowe TM. Discovery of permuted and recently split transfer RNAs in Archaea. Genome Biol 2011; 12:R38. [PMID: 21489296 PMCID: PMC3218864 DOI: 10.1186/gb-2011-12-4-r38] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 03/30/2011] [Accepted: 04/13/2011] [Indexed: 01/19/2023] Open
Abstract
Background As in eukaryotes, precursor transfer RNAs in Archaea often contain introns that are removed in tRNA maturation. Two unrelated archaeal species display unique pre-tRNA processing complexity in the form of split tRNA genes, in which two to three segments of tRNAs are transcribed from different loci, then trans-spliced to form a mature tRNA. Another rare type of pre-tRNA, found only in eukaryotic algae, is permuted, where the 3' half is encoded upstream of the 5' half, and must be processed to be functional. Results Using an improved version of the gene-finding program tRNAscan-SE, comparative analyses and experimental verifications, we have now identified four novel trans-spliced tRNA genes, each in a different species of the Desulfurococcales branch of the Archaea: tRNAAsp(GUC) in Aeropyrum pernix and Thermosphaera aggregans, and tRNALys(CUU) in Staphylothermus hellenicus and Staphylothermus marinus. Each of these includes features surprisingly similar to previously studied split tRNAs, yet comparative genomic context analysis and phylogenetic distribution suggest several independent, relatively recent splitting events. Additionally, we identified the first examples of permuted tRNA genes in Archaea: tRNAiMet(CAU) and tRNATyr(GUA) in Thermofilum pendens, which appear to be permuted in the same arrangement seen previously in red alga. Conclusions Our findings illustrate that split tRNAs are sporadically spread across a major branch of the Archaea, and that permuted tRNAs are a new shared characteristic between archaeal and eukaryotic species. The split tRNA discoveries also provide new clues to their evolutionary history, supporting hypotheses for recent acquisition via viral or other mobile elements.
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Affiliation(s)
- Patricia P Chan
- Department of Biomolecular Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
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Rodin AS, Szathmáry E, Rodin SN. On origin of genetic code and tRNA before translation. Biol Direct 2011; 6:14. [PMID: 21342520 PMCID: PMC3050877 DOI: 10.1186/1745-6150-6-14] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 02/22/2011] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Synthesis of proteins is based on the genetic code - a nearly universal assignment of codons to amino acids (aas). A major challenge to the understanding of the origins of this assignment is the archetypal "key-lock vs. frozen accident" dilemma. Here we re-examine this dilemma in light of 1) the fundamental veto on "foresight evolution", 2) modular structures of tRNAs and aminoacyl-tRNA synthetases, and 3) the updated library of aa-binding sites in RNA aptamers successfully selected in vitro for eight amino acids. RESULTS The aa-binding sites of arginine, isoleucine and tyrosine contain both their cognate triplets, anticodons and codons. We have noticed that these cases might be associated with palindrome-dinucleotides. For example, one-base shift to the left brings arginine codons CGN, with CG at 1-2 positions, to the respective anticodons NCG, with CG at 2-3 positions. Formally, the concomitant presence of codons and anticodons is also expected in the reverse situation, with codons containing palindrome-dinucleotides at their 2-3 positions, and anticodons exhibiting them at 1-2 positions. A closer analysis reveals that, surprisingly, RNA binding sites for Arg, Ile and Tyr "prefer" (exactly as in the actual genetic code) the anticodon(2-3)/codon(1-2) tetramers to their anticodon(1-2)/codon(2-3) counterparts, despite the seemingly perfect symmetry of the latter. However, since in vitro selection of aa-specific RNA aptamers apparently had nothing to do with translation, this striking preference provides a new strong support to the notion of the genetic code emerging before translation, in response to catalytic (and possibly other) needs of ancient RNA life. Consistently with the pre-translation origin of the code, we propose here a new model of tRNA origin by the gradual, Fibonacci process-like, elongation of a tRNA molecule from a primordial coding triplet and 5'DCCA3' quadruplet (D is a base-determinator) to the eventual 76 base-long cloverleaf-shaped molecule. CONCLUSION Taken together, our findings necessarily imply that primordial tRNAs, tRNA aminoacylating ribozymes, and (later) the translation machinery in general have been co-evolving to ''fit'' the (likely already defined) genetic code, rather than the opposite way around. Coding triplets in this primal pre-translational code were likely similar to the anticodons, with second and third nucleotides being more important than the less specific first one. Later, when the code was expanding in co-evolution with the translation apparatus, the importance of 2-3 nucleotides of coding triplets "transferred" to the 1-2 nucleotides of their complements, thus distinguishing anticodons from codons. This evolutionary primacy of anticodons in genetic coding makes the hypothesis of primal stereo-chemical affinity between amino acids and cognate triplets, the hypothesis of coding coenzyme handles for amino acids, the hypothesis of tRNA-like genomic 3' tags suggesting that tRNAs originated in replication, and the hypothesis of ancient ribozymes-mediated operational code of tRNA aminoacylation not mutually contradicting but rather co-existing in harmony.
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Affiliation(s)
- Andrei S Rodin
- Human Genetics Center, School of Public Health, University of Texas, Houston, TX 77225, USA
- Collegium Budapest (Institute for Advanced Study), Szentháromság u. 2, H-1014 Budapest, Hungary
| | - Eörs Szathmáry
- Collegium Budapest (Institute for Advanced Study), Szentháromság u. 2, H-1014 Budapest, Hungary
- Parmenides Center for the Study of Thinking, Kirchplatz 1, D-82049 Munich/Pullach, Germany
- Institute of Biology, Eötvös University, 1c Pázmány Péter sétány, H-1117 Budapest, Hungary
| | - Sergei N Rodin
- Collegium Budapest (Institute for Advanced Study), Szentháromság u. 2, H-1014 Budapest, Hungary
- Department of Molecular and Cellular Biology, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA
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Fujishima K, Sugahara J, Tomita M, Kanai A. Large-scale tRNA intron transposition in the archaeal order Thermoproteales represents a novel mechanism of intron gain. Mol Biol Evol 2010; 27:2233-43. [PMID: 20430862 DOI: 10.1093/molbev/msq111] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Recently, diverse arrangements of transfer RNA (tRNA) genes have been found in the domain Archaea, in which the tRNA is interrupted by a maximum of three introns or is even fragmented into two or three genes. Whereas most of the eukaryotic tRNA introns are inserted strictly at the canonical nucleotide position (37/38), archaeal intron-containing tRNAs have a wide diversity of small tRNA introns, which differ in their numbers and locations. This feature is especially pronounced in the archaeal order Thermoproteales. In this study, we performed a comprehensive sequence comparison of 286 tRNA introns and their genes in seven Thermoproteales species to clarify how these introns have emerged and diversified during tRNA gene evolution. We identified 46 intron groups containing sets of highly similar sequences (>70%) and showed that 16 of them contain sequences from evolutionarily distinct tRNA genes. The phylogeny of these 16 intron groups indicates that transposition events have occurred at least seven times throughout the evolution of Thermoproteales. These findings suggest that frequent intron transposition occurs among the tRNA genes of Thermoproteales. Further computational analysis revealed limited insertion positions and corresponding amino acid types of tRNA genes. This has arisen because the bulge-helix-bulge splicing motif is required at the newly transposed position if the pre-tRNA is to be correctly processed. These results clearly demonstrate a newly identified mechanism that facilitates the late gain of short introns at various noncanonical positions in archaeal tRNAs.
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Affiliation(s)
- Kosuke Fujishima
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
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