TY - JOUR. T1 - An orthogonal amber initiator tRNA functions similarly across diverse Escherichia coli laboratory strains. AU - Vincent, Russel. AU - Yiasemides, Pandelitsa. AU - Jaschke, Paul. N1 - Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.. PY - 2019/5/1. Y1 - 2019/5/1. N2 - Translation initiation is a sequential process involving interactions between the 30S small ribosomal subunit, initiation factors and initiator tRNA. The Escherichia coli K-12 strain is unique in the Escherichia because it has two different initiator tRNA sequences, tRNAfMet1 encoded by the metZWV genes and tRNAfMet2 encoded by the metY gene. A mutant of the metY gene was previously made where the anticodon sequence, responsible for specifying the start codon where translation initiation begins, was changed so that it bound to the amber stop codon UAG instead of the usual AUG start codon[1]. ...
TY - JOUR. T1 - Inhibitory Effect of Complex Formation with Oligodeoxyribonucleotide ethyl Phosphotriesters on Transfer Ribonucleic Acid Aminoacylation. AU - Barrett, J. C.. AU - Miller, Paul S.. AU - Tso, Paul O.P.. PY - 1974/11/1. Y1 - 1974/11/1. N2 - The oligodeoxyribonucleotide ethyl phosphotriesters d-Tp(Et)Gp(Et)G and d-Tp(Et)Tp(Et)Cp(Et)A, which are complementary to the 3′-CpCpA terminus and -UpGpApA- anticodon region, respectively, of tRNAphe coli have been used as in vitro probes of the structure and function of tRNA. The effect of these triesters on the aminoacyl-tRNA synthetase catalyzed aminoacylation of tRNA was examined. At 0° both triesters inhibit the formation of phenylalanyl-tRNAphe by approximately 50-60%. The inhibition decreases with increasing temperature. A Lineweaver-Burk analysis at 0° shows that the inhibition by both triesters is competitive in nature. The results suggest that the inhibition is a consequence of the formation of complexes between the triesters and ...
Ribonuclease bound to transfer RNA. Computer model showing the molecular structure of a ribonuclease Z (RNase Z, blue) enzyme bound to a transfer RNA (tRNA) molecule (red). RNase is a type of nuclease that catalyses the degradation of RNA (ribonucleic acid) into smaller components in preparation for other genetic processes. tRNA is RNA that transfers a specific active amino acid to a growing polypeptide chain at the site of protein synthesis during gene translation. RNase Z causes conformational changes in both molecules to promote reorganization of the catalytic site and tRNA cleavage. - Stock Image C008/8444
Ribonuclease bound to transfer RNA, molecular model. This complex consists of the ribonuclease Z (RNase Z, green and pink) enzyme bound to a transfer RNA (tRNA) molecule (orange and blue). RNase is a type of nuclease that catalyses the degradation of RNA (ribonucleic acid) into smaller components in preparation for other genetic processes. tRNA is RNA that transfers a specific active amino acid to a growing polypeptide chain at the site of protein synthesis during gene translation. RNase Z causes conformational changes to promote reorganization of the catalytic site and tRNA cleavage. - Stock Image C025/1923
Byrne R.T., Jenkins H.T., Peters D.T., Whelan F., Stowell J., Aziz N., Kasatsky P., Rodnina M.V., Koonin E.V., Konevega A.L., Antson A.A.. The reduction of specific uridines to dihydrouridine is one of the most common modifications in tRNA. Increased levels of the dihydrouridine modification are associated with cancer. Dihydrouridine synthases (Dus) from different subfamilies selectively reduce distinct uridines, located at spatially unique positions of folded tRNA, into dihydrouridine. Because the catalytic center of all Dus enzymes is conserved, it is unclear how the same protein fold can be reprogrammed to ensure that nucleotides exposed at spatially distinct faces of tRNA can be accommodated in the same active site. We show that the Escherichia coli DusC is specific toward U16 of tRNA. Unexpectedly, crystal structures of DusC complexes with tRNA(Phe) and tRNA(Trp) show that Dus subfamilies that selectively modify U16 or U20 in tRNA adopt identical folds but bind their respective tRNA ...
Transfer RNAs (tRNAs) function in translational machinery and further serves as a source of short non-coding RNAs (ncRNAs). tRNA-derived ncRNAs show differential expression profiles and play roles in many biological processes beyond translation. Molecular mechanisms that shape and regulate their expression profiles are largely unknown. Here, we report the mechanism of biogenesis for tRNA-derived Piwi-interacting RNAs (td-piRNAs) expressed in Bombyx BmN4 cells. In the cells, two cytoplasmic tRNA species, tRNAAspGUC and tRNAHisGUG, served as major sources for td-piRNAs, which were derived from the 5-part of the respective tRNAs. cP-RNA-seq identified the two tRNAs as major substrates for the 5-tRNA halves as well, suggesting a previously uncharacterized link between 5-tRNA halves and td-piRNAs. An increase in levels of the 5-tRNA halves, induced by BmNSun2 knockdown, enhanced the td-piRNA expression levels without quantitative change in mature tRNAs, indicating that 5-tRNA halves, not mature tRNAs,
The rapid progress of research in the tRNA field and recent advances in the understanding of the molecular basis of specificity in tRNA: protein interactions make it necessary to have all of the accumulated information in an easily accessible form. The purpose of this book is to fulfill that need by providing an up-to-date account of all aspects of research on transfer RNA, including its structure, biosynthesis, and interactions with the many proteins involved in protein biosynthesis. Beginning with an historical account, the book covers a broad area of research on tRNA biosynthesis, the different functions of tRNA in the genetic decoding process, its association with many different proteins, and the emerging rules governing the specificity of their interactions. In view of the impressive progress made in the last few years, several of the chapters are devoted to discussion of aminoacyl-tRNA synthetase tRNA interactions. An appendix containing the structural formulae of all modified nucleosides found in
R-loops at tRNA genes affect pre-tRNA synthesis in strains lacking topoisomerase and RNase H activities.A-E: Wild-type strain BY4741 (WT) and isogenic mutant
Post-transcriptional tRNA modifications play a primordial role in the translation process as they influence tRNA stability and folding, cognate codon recognition, stabilization of the codon-anticodon wobble base pairing and correct aminoacylation. In the last years, the awareness is growing that post-transcriptional tRNA modifications, especially at the wobble position, might regulate important cellular processes at the level of protein translation. One of our goals is to decipher the structure, function and regulation of these enzyme complexes in order to contribute to our understanding of their cellular roles and the way they are incorporated in signalling networks. In collaboration with the group of L. Droogmans (ULB, Belgium) we are also investigating the structure and function of a variety of methyltransferases in order to get a better understanding of their tRNA specificity and the contribution of their catalytic and RNA-binding domains to catalysis and substrate binding.. ...
Contributors : Y Perkarsky ; C M CroceSeries Type : Non-coding RNA profiling by high throughput sequencingOrganism : Homo sapiensWe analyzed small RNA sequencing data from CD5+/CD19+ B cells of a cohort of indolent and aggressive CLL patients compared with CD19+ B-cells of healthy donors.We identified tsRNA signatures in indolent and aggressive CLL vs. normal B-cells; we also found a drastic dysre...
Amino Acyl Transfer RNA: Intermediates in protein biosynthesis. The compounds are formed from amino acids, ATP and transfer RNA, a reaction catalyzed by aminoacyl tRNA synthetase. They are key compounds in the genetic translation process.
The site on the tRNA molecule that is bound to the aminoacetyl synthetase. In the case of yeast phenylalanine tRNA, this region is located adjacent to the dihydrouridine loop and consists of the four nucleotide pairs bracketed by arrows on the tRNA on page 397. See Chronology, 1971, Dudock et al.; amino acid activation, transfer RNA. ...
Students who plan to transfer to a four year college or university and earn a bachelors degree in this discipline should consult with a counselor or visit the Transfer/Career Center to determine the appropriate major preparation courses for their specific transfer institution and major. Transfer students may also earn an Associate of Arts degree in Liberal Arts and Sciences with an emphasis. This degree may be individually tailored to each students specific transfer requirements in order to provide the most efficient path to transfer. More information on transfer programs and procedures is available in the Transfer Programs section of the catalog. ...
Author: Labuda, D. et al.; Genre: Journal Article; Published in Print: 1984; Title: Mechanism of codon recognition by transfer RNA and codon-induced tRNA association.
refers to tRNA(Arg-Asp) dimeric genes. **, Suppressors, as defined in MIPS annotations, supplemented by items from tables 8 and 10 in Hinnebusch and Liebmann, 1982. Note: Nomenclature of tRNA species generally follows earlier conventions; in some cases, new indices were assigned to those tRNA subspecies that had not unequivocally been numbered thus far or that were detected by sequencing. ...
Transfer RNA, or tRNA, is responsible for decoding another type of RNA, messenger RNA or mRNA, in order to carry out the process of protein synthesis. Different types of tRNA exist, each of which...
We have obtained functional data for every possible single mutation, for about 14,000 double mutations, and for about 30,000 more highly mutated variants. Surprisingly, 37% of the single mutants retained at least some function. In addition, around 10% of double mutants showed near wild type levels of fluorescence, indicating that despite all of the modifications and structure constraints, tRNA function is relatively robust to mutation. We have also examined mutant performance in a yeast strain with a mutated Rapid tRNA Decay (RTD) quality control pathway, which degrades misfolded or unmodified tRNA. By comparing the performance of tRNA variants in the wild type strain and the decay pathway mutant, we have identified many new targets of this pathway. The majority of these new decay pathway targets are located in parts of the tRNA not previously known to be monitored by the RTD system, such as the anticodon and D stems. By examining the double mutants in relation to their constituent singles, we ...
... definition, a small RNA molecule, consisting of a strand of nucleotides folded into a clover-leaf shape, that picks up an unattached amino acid within the cell cytoplasm and conveys it to the ribosome for protein synthesis. See more.
In the present work, we compared the initiation mechanism of the hisR promoter to that of mutant derivatives carrying sequence changes in the discriminator region. The main characteristic of the wild‐type promoter is its resistance to melting: the promoter cannot be trapped in open configuration in vivo and does not form heparin‐resistant transcription complexes in vitro unless the initiating nucleotides are supplied to allow formation of the first dinucleotide bond. Both of these features, which are atypical for eubacterial sigma 70 promoters, can be relieved or suppressed by discriminator changes. In particular, the PhisRhpa variant, where the C-G‐rich stretch between −5 and +1 is replaced with an A-T‐rich sequence, is readily found open in rifampicin‐treated cells and shows no nucleotide requirements for formation of stable initiation complexes in vitro. These data suggest that the discriminator sequence can direct the initiation programme, most likely by setting the energy ...
Experimental evolution and systematic sequence analysis of transfer RNA genes reveal that anticodon mutations provide adaptive plasticity to the translation machinery.
Cape Town City chairman John Comitis says Ayanda Patosi needs to lose weight, and revealed the clubs interest in Bafana midfielder Mandla Masango.
Catalyzes the specific attachment of an amino acid to its cognate tRNA in a two step reaction: the amino acid, AA is first activated by ATP to form AA-AMP and then transferred to the acceptor end of the tRNA. Exhibits a post-transfer editing activity to hydrolyze mischarged tRNAs. {ECO:0000269,PubMed:19426743 ...
转运核糖核酸(Transfer RNA),又称传送核糖核酸、转移核糖核酸,通常简称为tRNA,是一种由76-90个核苷酸所组成的RNA[1],其3端可以在氨酰-tRNA合成酶催化之下,接附特定种类的氨基酸。转译的过程中,tRNA可借由自身的反密码子识别mRNA上的密码子,将该密码子对应的氨基酸转运至核糖体合成中的多肽链上。每个tRNA分子理论上只能与一种氨基酸接附,但是遗传密码有简并性(degeneracy),使得有多于一个以上的tRNA可以跟一种氨基酸接附。
mRNA and tRNA are both nucleic acids involved in the production of proteins. The body uses mRNA to make enzymes, while tRNA acts...
Consistent with other studies, we found that successful consolidations focused on reducing social transfers, which in the American context means entitlements, and also on cuts to the size and pay of the government work force. A 1996 International Monetary Fund study concluded that "fiscal consolidation that concentrates on the expenditure side, and especially on transfers and government wages, is more likely to succeed in reducing the public debt ratio than tax-based consolidation." For example, in the U.Ks 1997 consolidation, cuts to transfers made up 32% of expenditure cuts, and cuts to government wages made up 21%. ...
Yep, 16 mg. Apparently, the 8 mg tabs are hard to come by so most pharmacies either give you 4 mg or 16mg. So I have to cut the pill in half and take half in the AM and half in the PM. Thank you Mary for pointing that out to me!!! I only take these this week Monday-Friday and stop on transfer day. This pill has a gross taste to it, probably because I have to cut it in half ...
Recent studies have established that glucose deprivation causes inhibition of the nuclear tRNA export process in S. cerevisiae (30, 46). While the mechanism responsible for regulating nuclear tRNA export in response to the glucose level is not understood, findings from this study strongly suggest that it is most likely due to the function of the nuclear tRNA export receptors and the intranuclear tRNA chaperone Utp8p being controlled by glucose availability (Fig. 4). How the glucose level influences Utp8p function in nuclear tRNA export is not known, but evidence obtained suggests that the ability of the tRNA export receptors to function in nuclear tRNA export in response to glucose availability is most likely related to regulation of nuclear reimport of the tRNA export receptors after a round of tRNA export to the cytoplasm (Fig. 3). This conclusion is in accordance with previous studies showing cytoplasmic accumulation of several nuclear export receptors, including the nuclear tRNA export ...
Shared traits between prokaryotes and eukaryotes are helpful in the understanding of the tree of life evolution. tRNA gene cluster, a particular feature in RNA gene organisation, has been demonstrated to be prevalent in bacteria and eukaryotes, but there is a gap concerning its occurrence in archaea. Despite the significant presence in the Bacteria and Eukarya domains, the role of the tRNA gene cluster is under debate. In Bacteria, it has been implicated with a faster cell growing and in the modulation of the tRNA transcription and translation process.(20) In contrast, some studies have not observed any improvement in the fitness of the organism by tRNA gene clusters. In addition, some of the genes from these clusters would be inactivated.(21) In eukaryotes, there is a negative correlation between clusters of tRNA genes and chromosomal stability, since they can act as barriers to DNA replication and the consequent formation of genomic fragile sites.(5) Besides that, the tRNA-derived fragments ...
K14218 tRNA-Ala; tRNA Ala K14218 tRNA-Ala; tRNA Ala K14218 tRNA-Ala; tRNA Ala K14219 tRNA-Arg; tRNA Arg K14219 tRNA-Arg; tRNA Arg K14219 tRNA-Arg; tRNA Arg K14219 tRNA-Arg; tRNA Arg K14220 tRNA-Asn; tRNA Asn K14220 tRNA-Asn; tRNA Asn K14220 tRNA-Asn; tRNA Asn K14221 tRNA-Asp; tRNA Asp K14221 tRNA-Asp; tRNA Asp K14221 tRNA-Asp; tRNA Asp K14222 tRNA-Cys; tRNA Cys K14223 tRNA-Gln; tRNA Gln K14224 tRNA-Glu; tRNA Glu K14224 tRNA-Glu; tRNA Glu K14224 tRNA-Glu; tRNA Glu K14224 tRNA-Glu; tRNA Glu K14225 tRNA-Gly; tRNA Gly K14225 tRNA-Gly; tRNA Gly K14225 tRNA-Gly; tRNA Gly K14225 tRNA-Gly; tRNA Gly K14225 tRNA-Gly; tRNA Gly K14225 tRNA-Gly; tRNA Gly K14225 tRNA-Gly; tRNA Gly K14226 tRNA-His; tRNA His K14226 tRNA-His; tRNA His K14227 tRNA-Ile; tRNA Ile K14228 tRNA-Leu; tRNA Leu K14228 tRNA-Leu; tRNA Leu K14228 tRNA-Leu; tRNA Leu K14228 tRNA-Leu; tRNA Leu K14228 tRNA-Leu; tRNA Leu K14228 tRNA-Leu; tRNA Leu K14228 tRNA-Leu; tRNA Leu K14229 tRNA-Lys; tRNA Lys K14229 tRNA-Lys; tRNA Lys K14230 tRNA-Met; tRNA ...
A computer program, ARAGORN, identifies tRNA and tmRNA genes. The program employs heuristic algorithms to predict tRNA secondary structure, based on homology with recognized tRNA consensus sequences and ability to form a base-paired cloverleaf. tmRNA genes are identified using a modified version of the BRUCE program. ARAGORN achieves a detection sensitivity of 99% from a set of 1290 eubacterial, eukaryotic and archaeal tRNA genes and detects all complete tmRNA sequences in the tmRNA database, improving on the performance of the BRUCE program. Recently discovered tmRNA genes in the chloroplasts of two species from the green algae lineage are detected. The output of the program reports the proposed tRNA secondary structure and, for tmRNA genes, the secondary structure of the tRNA domain, the tmRNA gene sequence, the tag peptide and a list of organisms with matching tmRNA peptide tags.. ...
Transfer ribonucleic acid1 is methylated after the molecule is synthesized; at least eight enzymes are involved in the transfer of methyl groups (derived from methionine). The time courses of methylation and synthesis of tRNA during rat liver regeneration have been compared in an in vivo radioisotopic study, using 6-orotic acid-14C and 3H-methyl-L-methionine as precursors in double label pulses. Liver regeneration is a synchronized system in which biochemical events of the cell cycle are separable. Transfer RNA methylation increase precedes by several hours tRNA synthesis during regeneration, although the curves overlap. A ratio of the relative rate of methylation to the relative rate of synthesis has been made; that curve positively correlates with the rise and fall of protein synthesis during regeneration. It is clear that methylation and synthesis of tRNA are only weakly coupled; changing methyl content of the tRNA "pool" resulting from differential tRNA methylase and polymerase activities ...
tRNAs are heavily decorated posttranscriptionally with numerous chemical modifications, which are essential for shaping up, fine tuning, and regulating all aspects of tRNA functioning. These chemical modifications are dynamically regulated and catalyzed by tRNA modification enzymes[1]. Mutations or dysregulation of tRNA modifiers have been associated with diseases. The emerging importance of tRNA modifications in diseases calls for additional work[2, 3]. How tRNA modifications are regulated by tRNA modification enzymes is in need to be studied ...
Plays a central role in 2-thiolation of mcm(5)S(2)U at tRNA wobble positions of tRNA(Lys), tRNA(Glu) and tRNA(Gln). Directly binds tRNAs and probably acts by catalyzing adenylation of tRNAs, an intermediate required for 2-thiolation. It is unclear whether it acts as a sulfurtransferase that transfers sulfur from thiocarboxylated URM1 onto the uridine of tRNAs at wobble position.
We have previously reported the isolation an characterization of a functional initiator tRNA gene, metA, and a second initiator tRNA-like sequence, metB, from Mycobacterium tuberculosis. Here we describe the fine mapping of the initiator tRNA gene locus of the avirulent (H37Ra) and virulent (H37Rv) strains of M. tuberculosis. The genomic blot analyses show that the 1.7 kb (harbouring metB) and the 6.0 kb BamHI (harbouring metA) fragments are linked. Further, sequencing of a portion of the 6.0 kb fragment, in conjunction with the sequence of the 1.7 kb fragment confirmed the presence of an IS6110 element in the vicinity of metB. The IS element is flanked by inverted (28 bp, with 3 contiguous mismatches in the middle) and direct (3 bp) repeats considered to be the hallmarks of IS6110 integration sites. The organization of the initiator tRNA gene locus is identical in both the H37Ra and H37Rv strains and they carry a single copy of the functional initiator tRNA gene. Interestingly, the fast growing ...
Sulfur-containing transfer ribonucleic acids (tRNAs) are ubiquitous biomolecules found in all organisms that possess a variety of functions. For decades, their roles in processes such as translation, structural stability, and cellular protection have been elucidated and appreciated. These thionucleosides are found in all types of bacteria; however, their biosynthetic pathways are distinct among different groups of bacteria. Considering that many of the thio-tRNA biosynthetic enzymes are absent in Gram-positive bacteria, recent studies have addressed how sulfur trafficking is regulated in these prokaryotic species. Interestingly, a novel proposal has been given for interplay among thionucleosides and the biosynthesis of other thiocofactors, through participation of shared-enzyme intermediates, the functions of which are impacted by the availability of substrate as well as metabolic demand of thiocofactors. This review describes the occurrence of thio-modifications in bacterial tRNA and current methods
The modified nucleoside 1-methyladenosine (m(1)A) is found at position 58 in the TPsiC loop of many eukaryotic tRNAs. The absence of m(1)A from all tRNAs in Saccharomyces cerevisiae mutants lacking Gcd10p elicits severe defects in processing and stability of initiator methionine tRNA (tRNA(i)(Met)). Gcd10p is found in a complex with Gcd14p, which contains conserved motifs for binding S-adenosylmethionine (AdoMet). These facts, plus our demonstration that gcd14Delta cells lacked m(1)A, strongly suggested that Gcd10p/Gcd14p complex is the yeast tRNA(m(1)A)methyltransferase [(m(1)A)MTase]. Supporting this prediction, affinity-purified Gcd10p/Gcd14p complexes used AdoMet as a methyl donor to synthesize m(1)A in either total tRNA or purified tRNA(i)(Met) lacking only this modification. Kinetic analysis of the purified complex revealed K(M) values for AdoMet or tRNA(i)(Met) of 5.0 microM and 2.5 nM, respectively. Mutations in the predicted AdoMet-binding domain destroyed GCD14 function in vivo and ...
Figure 2. tRNA pools are coordinated with the alterations in the mRNA transcriptomes with different codon usage under differentiation or proliferation conditions. The repertoire has the effects on the cell fate determination.. tRNA repertoire and disease. tRNA repertoire has fundamental impact in human diseases. Many diseases are associated with the disrupted tRNAs levels. Dysregulation of certain tRNAs can induce tumorigenesis and cancer progression.. Cancer. After cataloging the tRNA repertoire, Gingold et al demonstrated the tRNA pools are different between cancer and differentiated non-cancer cells[4]. tRNAs that are upregulated in differentiated/arrested cells are repressed in proliferating cells. Conversely, tRNAs whose levels are high in proliferating cells become low in differentiated/arrested cells. Cancer cells adjust their tRNA pools to selectively bolster translation of the mRNAs that are required for tumor progression. By comparing tRNA expression in tumor versus normal breast ...
In all organisms, precursor tRNAs are processed into mature functional units by post-transcriptional changes. These involve 5 and 3 end trimming as well as the addition of a significant number of chemical modifications, including RNA editing. The only known example of non-organellar C to U editing of tRNAs occurs in trypanosomatids. In this system, editing at position 32 of the anticodon loop of tRNA(Thr)(AGU) stimulates, but is not required for, the subsequent formation of inosine at position 34. In the present work, we expand the number of C to U edited tRNAs to include all the threonyl tRNA isoacceptors. Notably, the absence of a naturally encoded adenosine, at position 34, in two of these isoacceptors demonstrates that A to I is not required for C to U editing. We also show that C to U editing is a nuclear event while A to I is cytoplasmic, where C to U editing at position 32 occurs in the precursor tRNA prior to 5 leader removal. Our data supports the view that C to U editing is more widespread
Shop tRNA-modifying protein ELISA Kit, Recombinant Protein and tRNA-modifying protein Antibody at MyBioSource. Custom ELISA Kit, Recombinant Protein and Antibody are available.
The 274 (active) tRNA genes in strain S288C can be grouped into 42 families of distinct codon specificity. The two methionine-specific tRNAs are counted as separate families, as initiator and elongator tRNAs are clearly distinguished both by primary structure and function. No tRNA(Sec) gene has been identified in yeast. No suppressor tRNA genes are found in this strain; Tables 1 and 1a list suppressors that have been identi fied as particular variants in other yeast strains . Table 4a presents a more detailed version of Table 4 by including cross-references to the tRNAs and tRNA genes the sequences of which had been determined prior to the yeast genome project. Figure 2. Codon usage in highly and lowly expressed yeast genes ...
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Author Summary Transfer RNAs are an important component of the translation machinery. Despite extensive biochemical investigations, a systems-level investigation of tRNAs functional roles in physiology, and genetic interactions among them, is lacking. We created a comprehensive tRNA deletion library in yeast and assessed the essentiality of each tRNA in multiple conditions. The majority of tRNA deletions showed no appreciable fitness defect when such strains were grown on rich medium. More challenging environmental conditions, however, revealed a richer set of specific-tRNA phenotypic defects. Co-deletion of tRNA combinations revealed that tRNAs with essential function can be compensated by members of the same or different anti-codon families. We often saw that identical tRNA gene copies contribute deferentially to fitness, suggesting that the genomic context of each gene can affect functionality. Genome-wide expression changes in response to tRNA deletions revealed two different responses. When a
A large number of post-transcriptional base modifications in transfer RNAs have been described (Sprinzl, M., Horn, C., Brown, M., Ioudovitch, A., and Steinberg, S. (1998) Nucleic Acids Res. 26, 148-153). These modifications enhance and expand tRNA function to increase cell viability. The intermediates and genes essential for base modifications in many instances remain unclear. An example is wyebutosine (yW), a fluorescent tricyclic modification of an invariant guanosine situated on the 3-side of the tRNA(Phe) anticodon. Although biosynthesis of yW involves several reaction steps, only a single pathway-specific enzyme has been identified (Kalhor, H. R., Penjwini, M., and Clarke, S. (2005) Biochem. Biophys. Res. Commun. 334, 433-440). We used comparative genomics analysis to identify a cluster of orthologous groups (COG0731) of wyosine family biosynthetic proteins. Gene knock-out and complementation studies in Saccharomyces cerevisiae established a role for YPL207w, a COG0731 ortholog that ...
With the advent of new and improved high-throughput sequencing technologies in the last few years, a growing number of novel classes of small RNA, other than miRNAs or siRNA, has emerged, which appear as new actors in gene expression regulation. tRNA-derived small RNAs represent one of these novel members that are, surprisingly, among the most conserved class of small RNAs throughout evolution. They could represent the most primitive small RNA pathways from which the well-known canonical RNA silencing pathways reported in higher eukaryotes evolved. This review aims to make a compilation of the most relevant research literature in this field with the purpose of shedding light on the relation of these primitive tRNA-derived molecules with the gene silencing machinery.
This chapter reviews what is known about the mechanism of precursor tRNA splicing: (i) the tRNA substrates for the splicing reaction, (ii) the enzymes involved in removing the introns to form the mature tRNA, (iii) interactions between these enzymes and their tRNA substrates and cofactors, (iv) the organization of tRNA splicing in the nucleus, (v) the identity of splicing mutants that affect the enzymatic machinery, (vi) current knowledge about the differences and similarities of tRNA splicing in systems of various organisms, and (vii) the possible function of tRNA introns.
Elongation requires the elongation factors,ref,Stryer, Biochemistry, Seventh edition, 2007: 936,/ref, EF-Tu, EF-Ts and EF-G as well as GTP to supply the energy. Elongation describes the process of aminoacyl tRNA molecules binding to the codon. A [[Peptide bond,peptide bond]] is formed between the amino acid of the tRNA in the P site and the amino acid in the tRNA molecule that has just arrived at the A site; the formation of this peptide bond is catalysed by the 23S subunit. The amino acid in the P site is released from its tRNA molecule and the ribosome moves along so as to transfer the tRNA currently in the A site into the P site. This step is known as transloaction. The uncharged tRNA i.e. tRNA without an amino acid, moves into the E (empty) site. ,ref,http://rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/translate.htm,/ref,,br ...
By the time Hoagland had joined Huntington Laboratories, his colleagues there were well known for their work in protein synthesis.[4] In the early 1950s Hoagland and his associates were able to show that polypeptide synthesis occurs on ribosomes. They did this by giving a rat injections of radioactive amino acids, waiting for a defined period of time, extracting the liver, and examining sub-cellular fractions for radioactivity. He found that after longer periods of times (hours, days) radioactively labeled proteins were present in all subcellular fractions. However, if they allowed less time to pass, radioactivity was found in only certain particles, which they deemed the sites of proteins synthesis. These particles were named ribosomes. During their experiments with rat liver cells, Hoagland and Zamecnik noticed that in the presence of ATP, amino acids associate with heat soluble RNA, which was later named transfer RNA (tRNA).[4] This amino acid and tRNA complex was later called aminoacyl-tRNA. ...
The tRNA substrates of TrmJ in Escherichia coli. (A) The cloverleaf structures of six E. coli tRNAs with a 2′-O-methylated ribose in position 32 from the MODO
摘 要:转移核糖核酸(tRNA) 的转录后修饰对tRNA 正常行使生物学功能具有重要意义,这些功能包括tRNA 的正确折叠和维持其稳定性、在核糖体上正确解码。虽然tRNA 转录后大部分核苷酸修饰形式在20世纪70 年代已被鉴定出,但最近才在大肠杆菌及酵母中鉴定出催化这些tRNA 核苷酸修饰的酶的绝大部分基因。这些修饰酶基因的鉴定为研究tRNA 转录后修饰的生物功能开启了新的大门。人胞质tRNA 和线粒体tRNA(mt tRNA) 都存在大量核苷酸修饰,这些修饰的缺陷常常与多种人类疾病相关。因此,研究tRNA核苷酸修饰有助于我们了解相关疾病的发病机理 ...
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