• Genomics & Informatics
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• v.16 no.4
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• pp.28.1-28.6
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• 2018

Due to the increasing interest in synonymous codons, several codon bias-related terms were introduced. As one measure of them, the tRNA adaptation index (tAI) was invented about a decade ago. The tAI is a measure of translational efficiency for a gene and is calculated based on the abundance of intracellular tRNA and the binding strength between a codon and a tRNA. The index has been widely used in various fields of molecular evolution, genetics, and pharmacology. Afterwards, an improved version of the index, named specific tRNA adaptation index (stAI), was developed by adapting tRNA copy numbers in species. Although a subsequently developed webserver (stAIcalc) provided tools that calculated stAI values, it was not available to access pre-calculated values. In addition to about 100 species in stAIcalc, we calculated stAI values for whole coding sequences in 148 species. To enable easy access to this index, we constructed a novel web database, named STADIUM (Species-specific tRNA adaptive index compendium). STADIUM provides not only the stAI value of each gene but also statistics based on pathway-based classification. The database is expected to help researchers who have interests in codon optimality and the role of synonymous codons. STADIUM is freely available at http://stadium.pmrc.re.kr.

• Korean Journal of Microbiology
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• v.45 no.2
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• pp.215-221
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• 2009

Site-specific incorporation of unnatural amino acids into proteins in vivo can be achieved by co-expression of an orthogonal pair of suppressor tRNA and engineered aminoacyl-tRNA synthetase (ARS) that specifically ligates an unnatural amino acid to the suppressor tRNA. As a step to establish this technique, here we generated an Escherichia coli reporter strain DH10B(Tn:lacZam) by integrating amber mutated lacZ gene into the chromosome of E. coli DH10B strain. In vivo expression of E. coli amber suppressor $tRNA^{Gln}$ produced blue colonies in culture plates containing X-Gal as well as dramatically increased $\beta$-galactosidase activity. In addition, expression of an orthogonal pair of Saccharomyces cerevisiae suppressor $tRNA^{Tyr}$ and tyrosyl-tRNA synthetase also produced blue colonies as well as moderate increase of $\beta$-galactosidase activity. These data demonstrate that our reporter strain will provide an efficient method to assess amber suppression in both qualitative and quantitative manners.

• Journal of Microbiology and Biotechnology
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• v.18 no.1
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• pp.23-27
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• 2008

Self-splicing group I introns in tRNA anticodon loops have been found in diverse groups of bacteria. In this work, we identified $tRNA^{fMet}$ group I introns in six strains of marine Synechococcus elongatus. Introns with sizes around 280 bp were consistently obtained in all the strains tested. In a phylogenetic analysis using the nucleotide sequence determined in this study with other cyanobacterial $tRNA^{fMet}$ and $tRNA^{Leu}$ intron sequences, the Synechococcus sequence was grouped together with the sequences from other unicellular cyanobacterial strains. Interestingly, the phylogenetic tree inferred from the intronic sequences clearly separates the different tRNA introns, suggesting that each family has its own evolutionary history.

• Korean Journal of Microbiology
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• v.50 no.1
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• pp.1-7
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• 2014

Site-specific incorporation of unnatural amino acids (SSIUA) into protein can be achieved in vivo by coexpression of an orthogonal pair of suppressor tRNA and engineered aminoacyl-tRNA synthetase (ARS) that specifically ligates an unnatural amino acid to the suppressor tRNA. As a step to develop the SSIUA technique in Escherichia coli, here we established a new 2-step screening system that can be used for selecting an ARS variant(s) that ligates an unnatural amino acid to a suppressor tRNA. A positive selection system consists of chloramphenicol acetyl transferase gene containing an amber mutation at the $27^{th}$ residue, and efficiently concentrated amber suppressible ARS with a maximum enrichment factor of $9.0{\times}10^5$. On the other hand, a negative selection system was constructed by adding multiple amber codons in front of a lethal gene encoding the control of cell death B toxin (ccdB) which acts as an inhibitory protein of bacterial topoisomerase II. Amber suppression of ccdB by an orthogonal pair of Saccharomyces cerevisiae tyrosyl-tRNA synthetase (TyrRS) and an amber suppressor tRNA significantly inhibits bacterial growth. This selection system was also able to efficiently remove amber suppressible ARS which could ligate natural amino acids to the suppressor tRNA. Thus, sequential combination of these two selection systems might be able to function as a powerful tool for selecting an ARS variant that specifically ligates an unnatural amino acid to the suppressor tRNA from an ARS mutant pool.

• Journal of Microbiology and Biotechnology
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• v.22 no.2
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• pp.190-198
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• 2012

RNA interference (RNAi) is rapidly becoming a valuable tool in biological studies, as it allows the selective and transient knockdown of protein expression. The short-interfering RNAs (siRNAs) transiently silence gene expression. By contrast, the expressed short-hairpin RNAs induce long-term, stable knockdown of their target gene. Trichoplusia ni (T. ni) cells are widely used for mammalian cell-derived glycoprotein expression using the baculovirus system. However, a suitable shRNA expression system has not been developed yet. We investigated the potency of shRNA-mediated gene expression inhibition using human and Drosophila U6 promoters in T. ni cells. Luciferase, EGFP, and ${\beta}$-N-acetylglucosaminidase (GlcNAcase) were employed as targets to investigate knockdown of specific genes in T. ni cells. Introduction of the shRNA expression vector under the control of human U6 or Drosophila U6 promoter into T. ni cells exhibited the reduced level of luciferase, EGFP, and ${\beta}$-N-acetylglucosaminidase compared with that of untransfected cells. The shRNA was expressed and processed to siRNA in our vector-transfected T. ni cells. GlcNAcase mRNA levels were down-regulated in T. ni cells transfected with shRNA vectors-targeted GlcNAcase as compared with the control vector-treated cells. It implied that our shRNA expression vectors using human and Drosophila U6 promoters were applied in T. ni cells for the specific gene knockdown.

• Applied Biological Chemistry
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• v.45 no.4
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• pp.190-194
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• 2002

Expression of Bacillus subtilis glutamyl-tRNA synthetase (GluRS) in Escherichia coli is lethal for the host, probably because this enzyme misaminoacylates ${tRNA_l}^{Gln}$ with glutamate in vivo. In order to overexpress B. subtilis GluRS, encoded by the gltX gene, in E. coli, this gene was amplified from B. subtilis 168 chromosomal DNA using PCR method and the entire coding region was cloned into a pET11a expression vector so that it was expressed under the control or the T7 Promoter. The resulting recombinant pEBER plasmid was transformed into E. coli Novablue (DE3) bearing the T7 RNA polymerase gene for expression. After IPTG treatment, the overproduced enzyme was purified using ammonium sulfate fractionation, Source Q anion exchange chromatography, Superdex-200 gel filtration, and Mono Q anion exchange chromatography. The purified enzyme yielded 18-fold increase in specific activity over the crude cell extract and its molecular weight was approximately 55 kDa on SDS-PAGE.

• Bulletin of the Korean Chemical Society
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• v.26 no.6
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• pp.921-924
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• 2005

It is known that metallothionein (MT) plays a role in the scavenging of free radicals, which is produced under various stress conditions. MT may function as an antioxidant that protects against oxidative damage of DNA, protein, and lipid induced by superoxide anion, hydrogen peroxide, hydroxyl radical, nitric oxide, and peroxynitrite. This study was undertaken to test the hypothesis that MT also protects from RNA damage induced by peroxynitrite, an important reactive nitrogen species that causes a diversity of pathological processes. A cell-free system was used. RNA damage was detected by the mobility of $tRNA^{Phe}$ in electrophoresis. Cleavages on tRNA were not induced by 3-morpholinosydnomine, which produces peroxynitrite directly. MT induced tRNA damage which was site specific.

• Journal of Plant Biology
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• v.26 no.1
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• pp.1-6
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• 1983

In order to investigate the effects of GA3 on RNA biosynthesis, the amounts of rRNA and tRNA in germinating maize seeds were measured. The amount of rRNA in the endospermless seedlings was remarkably increased by GA3 tretment after 48 h of germination, but no effect was observed after 12 h of germination. While the amout of rRNA in 0.5 cm shoots in length was decreased by GA3 treatment, both of the amounts of rRNA and tRNA were increased in 1~1.5 cm shoots. According to the above mentioned results, it may be suggested that RNA biosynthesis is affected by GA3 treatment, and that GA3 participates in the biosynthesis of rRNA rather than tRNA in germinating maize seeds.

• Parasites, Hosts and Diseases
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• v.51 no.4
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• pp.401-412
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• 2013

Because of an increased number of Acanthamoeba keratitis (AK) along with associated disease burdens, medical professionals have become more aware of this pathogen in recent years. In this study, by analyzing both the nuclear 18S small subunit ribosomal RNA (18S rRNA) and mitochondrial 16S rRNA gene loci, 27 clinical Acanthamoeba strains that caused AK in Japan were classified into 3 genotypes, T3 (3 strains), T4 (23 strains), and T5 (one strain). Most haplotypes were identical to the reference haplotypes reported from all over the world, and thus no specificity of the haplotype distribution in Japan was found. The T4 sub-genotype analysis using the 16S rRNA gene locus also revealed a clear subconformation within the T4 cluster, and lead to the recognition of a new sub-genotype T4i, in addition to the previously reported sub-genotypes T4a-T4h. Furthermore, 9 out of 23 strains in the T4 genotype were identified to a specific haplotype (AF479533), which seems to be a causal haplotype of AK. While heterozygous nuclear haplotypes were observed from 2 strains, the mitochondrial haplotypes were homozygous as T4 genotype in the both strains, and suggested a possibility of nuclear hybridization (mating reproduction) between different strains in Acanthamoeba. The nuclear 18S rRNA gene and mitochondrial 16S rRNA gene loci of Acanthamoeba spp. possess different unique characteristics usable for the genotyping analyses, and those specific features could contribute to the establishment of molecular taxonomy for the species complex of Acanthamoeba.

• The Journal of Natural Sciences
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• v.14 no.2
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• pp.83-91
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• 2004

Recently phage K11 lysozyme was cloned and characterized in our lab. The K11 lysozyme was identified to have dual functions. It not only cuts a peptidoglycan bond in bacterial cell wall but also acts as an inhibitor of K11 RNA polymerase. It has been known that the T7 lysozyme binds specifically to T7 RNA polymerase and inhibits transcription. The dual activities of K11 lysozyme are atreeable to the case of T7 phage lysozyme and RNA polymerare. In order to identify the binding magnitude of K11 lysozyme with K11 RNA polymerase, yeast two-hybrid system was used. K11 phage lysozyme gene was introduced into pLexA plasmid and used as a prey. Also, K11 phage RNA polymerase gene was introduced into pJG4-5 and used as a bait. The binding between K11 lysozyme and K11 RNA polymerase was demonstrated by expression of reporter genes such as lacZ and leu2.