1
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Abstract
Promoter-specific transcription by silkworm RNA polymerase III is dependent on several transcription factors (TFs) in addition to the polymerase itself. The activities present in silk gland nuclear extracts that are necessary to reconstitute transcription from class III genes in vitro have been resolved into several partially purified components. These include TFIIIR, which is unusual because it is composed of RNA. Here, we identify the RNA that provides TFIIIR activity as silkworm tRNA(IleIAU). This conclusion is based on copurification of tRNA(IleIAU) with TFIIIR activity, TFIIIR activity in synthetic tRNA(Ile), and hybrid selection of TFIIIR activity by antisense tRNA(IleIAU). We have tested the ability of a variety of other tRNAs to stimulate transcription and find that TFIIIR activity is highly specific to silkworm tRNA(IleIAU).
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2
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Abstract
Promoter-specific transcription by silkworm RNA polymerase III is dependent on several transcription factors (TFs) in addition to the polymerase itself. The activities present in silk gland nuclear extracts that are necessary to reconstitute transcription from class III genes in vitro have been resolved into several partially purified components. These include TFIIIR, which is unusual because it is composed of RNA. Here, we identify the RNA that provides TFIIIR activity as silkworm tRNA(IleIAU). This conclusion is based on copurification of tRNA(IleIAU) with TFIIIR activity, TFIIIR activity in synthetic tRNA(Ile), and hybrid selection of TFIIIR activity by antisense tRNA(IleIAU). We have tested the ability of a variety of other tRNAs to stimulate transcription and find that TFIIIR activity is highly specific to silkworm tRNA(IleIAU).
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MESH Headings
- Animals
- Base Sequence
- Bombyx/genetics
- Bombyx/metabolism
- Cell Nucleus/metabolism
- Chromatography, Thin Layer
- Cloning, Molecular
- Electrophoresis, Polyacrylamide Gel
- Genetic Complementation Test
- Kinetics
- Molecular Sequence Data
- Nucleic Acid Conformation
- Plasmids
- Promoter Regions, Genetic
- RNA Polymerase III/metabolism
- RNA, Transfer, Ile/biosynthesis
- RNA, Transfer, Ile/chemistry
- RNA, Transfer, Ile/isolation & purification
- Sequence Homology, Nucleic Acid
- Transcription Factors/chemistry
- Transcription Factors, TFII
- Transcription, Genetic
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Affiliation(s)
- H M Dunstan
- Institute of Molecular Biology, University of Oregon, Eugene 97403
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3
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Kannan P, Buettner R, Pratt DR, Tainsky MA. Identification of a retinoic acid-inducible endogenous retroviral transcript in the human teratocarcinoma-derived cell line PA-1. J Virol 1991; 65:6343-8. [PMID: 1920638 PMCID: PMC250352 DOI: 10.1128/jvi.65.11.6343-6348.1991] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Retinoic acid (RA), a developmental morphogen, causes activation of a transcript of an endogenous retrovirus-related element in the human teratocarcinoma-derived cell line PA-1. This provirus is defective, and the provirus-related sequences exist as multicopy elements (more than 20 copies) in human DNA. This is the first human endogenous retroviral mRNA that is known to be transcriptionally activated by RA. The nucleotide sequence of the 3,357 bp of this viral cDNA was determined and shows a strong homology to the type C-related human endogenous retroviral proviruses ERV3 and 4-1. This cDNA contains 'R-U5-delta pol-env-U3-R sequences of the provirus. Adjacent to the putative 5' long terminal repeat of this provirus there is an 18-bp sequence complementary to the 3' end of isoleucine tRNA. We named this RA-responsive virus RRHERV-I.
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Affiliation(s)
- P Kannan
- Department of Tumor Biology, University of Texas M.D. Anderson Cancer Center, Houston 77030
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4
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Leung J, Sinclair DA, Hayashi S, Tener GM, Grigliatti TA. Informational redundancy of tRNA(4Ser) and tRNA(7Ser) genes in Drosophila melanogaster and evidence for intergenic recombination. J Mol Biol 1991; 219:175-88. [PMID: 1903816 DOI: 10.1016/0022-2836(91)90560-s] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Variant tRNA genes have been widely observed in multicellular eukaryotes. Recent biochemical studies have shown that some of them are expressed in a tissue- or a stage-specific manner. These findings would thus imply that certain modified tRNAs may be crucial for the development of the organism. Using Drosophila melanogaster as a model, we have taken a combined genetic and molecular approach to examine critically the possible biological functions of tRNA(4, 7Ser) genes. We showed that at least 50% of the total templates can be deleted from the genome without inducing abnormal phenotypes such as Minute, or a decrease in viability. In addition, two of the tRNASer variant genes that are unique in sequence are also completely dispensable. This strongly implies that even though they may be expressed in vivo, they play no essential role in the development of the fruitfly. By comparison with some of the corresponding tRNA genes in another sibling species, Drosophila erecta, our results suggest strongly that the variants are products non-reciprocal exchanges among the tRNA(4, 7Ser), genes. Such intergenic recombination events may have a major influence in the concerted evolution of the two gene families.
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Affiliation(s)
- J Leung
- Department of Zoology, University of British Columbia, Vancouver, Canada
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5
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Sprinzl M, Dank N, Nock S, Schön A. Compilation of tRNA sequences and sequences of tRNA genes. Nucleic Acids Res 1991; 19 Suppl:2127-71. [PMID: 2041802 PMCID: PMC331350 DOI: 10.1093/nar/19.suppl.2127] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Affiliation(s)
- M Sprinzl
- Laboratorium für Biochemie, Universität Bayreuth, FRG
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6
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Reddy PS, Padayatty JD. Effects of 5' flanking sequences and changes in the 5' internal control region on the transcription of rice tRNA % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaqcKbay-haafaqabe% GabaaabaGaae4raiaabYgacaqG5baabaGaae4raiaaboeacaqGdbaa% aaaa!3CC7!\[\begin{array}{*{20}c} {{\text{Gly}}} \\ {{\text{GCC}}} \\ \end{array} \]. PLANT MOLECULAR BIOLOGY 1988; 11:575-583. [PMID: 24272491 DOI: 10.1007/bf00017457] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/1988] [Accepted: 08/10/1988] [Indexed: 06/02/2023]
Abstract
A stretch of 71 nucleotides in a 1.2 kilobase pair Pst I fragment of rice DNA was identified as tRNA% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaqcaauaauaabeqace% aaaeaacaqGhbGaaeiBaiaabccacaqG5baabaGaae4raiaaboeacaqG% dbaaaaaa!3BE7!\[\begin{array}{*{20}c} {{\text{Gl y}}} \\ {{\text{GCC}}} \\ \end{array} \] gene by hybridization and nucleotide sequence analyses. The hybridization of genomic DNA with the tRNA gene showed that there are about 10 glycine tRNA genes per diploid rice genome. The 3' and 5' internal control regions, where RNA polymerase III and transcription factors bind, were found to be present in the coding sequence. The gene was transcribed into a 4S product in an yeast cell-free extract. The substitution of 5' internal control region with analogous sequences from either M13mp19 or M13mp18 DNA did not affect the transcription of the gene in vitro. The changes in three highly conserved nucleotides in the consensus 5' internal control region (RGYNNARYGG; R = purine, Y = pyrimidine, N = any nucleotide) did not affect transcription showing that these nucleotides are not essential for promotion of transcription. There were two 16 base pair repeats, 'TGTTTGTTTCAGCTTA' at -130 and -375 positions upstream from the start of the gene. Deletion of 5' flanking sequences including the 16 base pair repeat at -375 showed increased transcription indicating that these sequences negatively modulate the expression of the gene.
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Affiliation(s)
- P S Reddy
- Department of Biochemistry, Indian Institute of Science, 560 012, Bangalore, India
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7
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Cribbs DL, Leung J, Newton CH, Hayashi S, Miller RC, Tener GM. Extensive microheterogeneity of serine tRNA genes from Drosophila melanogaster. J Mol Biol 1987; 197:397-404. [PMID: 3126300 DOI: 10.1016/0022-2836(87)90553-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The nucleotide sequences of nine genes corresponding to tRNA(Ser)4 or tRNA(Ser)7 of Drosophila melanogaster were determined. Eight of the genes compose the major tRNA(Ser)4,7 cluster at 12DE on the X chromosome, while the other is from 23E on the left arm of chromosome 2. Among the eight X-linked genes, five different, interrelated, classes of sequence were found. Four of the eight genes correspond to tRNA(Ser)4 and tRNA(Ser)7 (which are 96% homologous), two appear to result from single crossovers between tRNA(Ser)4 and tRNA(Ser)7 genes, one is an apparent double crossover product, and the last differs from a tRNA(Ser)4 gene by a single C to T transition at position 50. The single autosomal gene corresponds to tRNA(Ser)7. Comparison of a pair of genes corresponding to tRNA(Ser)4 from D. melanogaster and Drosophila simulans showed that, while gene flanking sequences may diverge considerably by accumulation of point changes, gene sequences are maintained intact. Our data indicate that recombination occurs between non-allelic tRNA(Ser) genes, and suggest that at least some recombinational events may be intergenic conversions.
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Affiliation(s)
- D L Cribbs
- Department of Biochemistry, University of British Columbia, Vancouver, Canada
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8
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Bertling W, Dingermann T, Kaiserwerth M. Comparative study of 5′ flanking sequences of eukaryotic genes: possible functional implications. Int J Biol Macromol 1987. [DOI: 10.1016/0141-8130(87)90028-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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9
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Saigo K. Unusual clustering of the genes for primer tRNAs for reverse transcription of retrotransposons in Drosophila. Nucleic Acids Res 1986; 14:9526. [PMID: 2432478 PMCID: PMC311977 DOI: 10.1093/nar/14.23.9526] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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10
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Lofquist A, Sharp S. The 5'-flanking sequences of Drosophila melanogaster tRNA5Asn genes differentially arrest RNA polymerase III. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)66913-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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11
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Green GA, Weil JH, Steinmetz A. The sequences of two nuclear genes and a pseudogene for tRNA(Pro) from the higher plant Phaseolus vulgaris. PLANT MOLECULAR BIOLOGY 1986; 7:207-212. [PMID: 24302306 DOI: 10.1007/bf00021332] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/1986] [Accepted: 06/10/1986] [Indexed: 06/02/2023]
Abstract
A genomic bank of nuclear DNA (nDNA) from the higher plant Phaseolus vulgaris, constructed using the lambda EMBL-4 vector, has been screened for the presence of tRNA genes. One of the many positive recombinants was found to hybridise several times stronger than the other positives, and has been shown to contain several tRNA genes. We report the structure of two nuclear tRNA genes for tRNA(Pro), namely tRNA(Pro)(UGG) and tRNA(Pro)(AGG), and that of a 'pseudogene' for tRNA(Pro). This 'pseudogene', despite showing 95% homology with the other tRNA(Pro) species presented here, has several features which are likely to affect its transcription or its functioning as a tRNA.
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Affiliation(s)
- G A Green
- Institut de Biologie Moléculaire et Cellulaire, Université Louis Pasteur, 15 rue Descartes, F-67084, Strasbourg, France
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12
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Wich G, Sibold L, Böck A. Genes for tRNA and their putative expression signals in Methanococcus. Syst Appl Microbiol 1986. [DOI: 10.1016/s0723-2020(86)80118-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Glew L, Lo R, Reece T, Nichols M, Söll D, Bell J. The nucleotide sequence, localization and transcriptional properties of a tRNALeuCUG gene from Drosophila melanogaster. Gene X 1986; 44:307-14. [PMID: 2946625 DOI: 10.1016/0378-1119(86)90195-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The nucleotide sequence of a tRNALeuCUG gene from Drosophila melanogaster has been determined and compared with available tRNALeuCUG sequences from other eukaryotes, as well as with the tRNALeuUUG gene of D. melanogaster. The genomic location, determined by in situ hybridization, was found to be at site 66B on chromosome 3L. This localization probably places it within one of the known, but uncharacterized, clusters of tRNA genes in this organism. In addition, the transcriptional behaviour of this tRNALeuCUG gene in various in vitro systems is described and it seems that, although the gene is transcribed in all test systems, the very A + T-rich 5'-flanking sequence of this particular gene may be somewhat inhibitory to transcription in vitro.
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14
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Pratt K, Eden FC, You KH, O'Neill VA, Hatfield D. Conserved sequences in both coding and 5' flanking regions of mammalian opal suppressor tRNA genes. Nucleic Acids Res 1985; 13:4765-75. [PMID: 4022772 PMCID: PMC321825 DOI: 10.1093/nar/13.13.4765] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The rabbit genome encodes an opal suppressor tRNA gene. The coding region is strictly conserved between the rabbit gene and the corresponding gene in the human genome. The rabbit opal suppressor gene contains the consensus sequence in the 3' internal control region but like the human and chicken genes, the rabbit 5' internal control region contains two additional nucleotides. The 5' flanking sequences of the rabbit and the human opal suppressor genes contain extensive regions of homology. A subset of these homologies is also present 5' to the chicken opal suppressor gene. Both the rabbit and the human genomes also encode a pseudogene. That of the rabbit lacks the 3' half of the coding region. Neither pseudogene has homologous regions to the 5' flanking regions of the genes. The presence of 5' homologies flanking only the transcribed genes and not the pseudogenes suggests that these regions may be regulatory control elements specifically involved in the expression of the eukaryotic opal suppressor gene. Moreover the strict conservation of coding sequences indicates functional importance for the opal suppressor tRNA genes.
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15
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Sharp SJ, Schaack J, Cooley L, Burke DJ, Söll D. Structure and transcription of eukaryotic tRNA genes. CRC CRITICAL REVIEWS IN BIOCHEMISTRY 1985; 19:107-44. [PMID: 3905254 DOI: 10.3109/10409238509082541] [Citation(s) in RCA: 210] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The availability of cloned tRNA genes and a variety of eukaryotic in vitro transcription systems allowed rapid progress during the past few years in the characterization of signals in the DNA-controlling gene transcription and in the processing of the precurser RNAs formed. This will be the subject matter discussed in this review.
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16
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KAULENAS MINDAUGASS. Molecular Biology: Protein Synthesis. Biochemistry 1985. [DOI: 10.1016/b978-0-08-030811-1.50014-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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17
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DeLotto R, Schedl P. A Drosophila melanogaster transfer RNA gene cluster at the cytogenetic locus 90BC. J Mol Biol 1984; 179:587-605. [PMID: 6094829 DOI: 10.1016/0022-2836(84)90157-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
We report the isolation and characterization of a 31 X 10(3) base-pair DNA segment containing a cluster of Drosophila melanogaster transfer RNA genes from the cytogenic locus 90BC. Seven distinct coding regions have been identified in a 15 X 10(3) base-pair DNA segment. These coding regions contain at least ten tRNA structural genes and include sequences encoding the following tRNAs: tRNAval, tRNAPro, tRNAAla and tRNAThr. We have determined the nucleotide sequence of six of these structural genes and their flanking regions. These genes do not contain intervening sequences nor do they encode the terminal CCA. The tRNA genes from the locus also appear to be functional when assayed in a Xenopus germinal vesicle in vitro transcriptional system.
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18
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Abstract
We have found a 371-base-pair (bp) repeated DNA element, tau, in Saccharomyces cerevisiae. The ends of tau are composed of a 5-bp inverted repeat, similar in sequence to those reported for the Ty, sigma, copia, and spleen necrosis virus elements. These inverted repeats are flanked by 5-bp direct repeats of a target sequence that occurs only once in an allele that lacks the tau element. This overall structure is characteristic of transposable elements. Like sigma, tau elements have been found (in both orientations) closely associated with tRNA genes (409 and 198 bp from the 5' end, respectively). It is noteworthy that one representative of tau was isolated in a concentric insertion of tau, delta, and sigma.
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19
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Abstract
The nucleotide sequence of tRNAIle from brewer's yeast Saccharomyces cerevisiae was determined. Its primary structure is pG-G-U-C-U-C-U-U-m1G-m2G- C-C-C-A-G-D-D-G-G-D-D-A-A-G-G-C-A-C-C-G-U-G-C-U-I-A-U-t6 A-A-C-G-C-G-G-G-GA-D-m5 C-A-G-C-G-G-T-psi-C-G-m1 A-U-C-C-C-G-C-U-A-G-A-G-A-C-C-A-C-C-A. Its anticodon is I-A-U. It should therefore recognize the three isoleucine codons and is for this reason probably the only isoacceptor tRNA for isoleucine in brewer's yeast. It presents a large homology with its counterpart from Torulopsis utilis (87%).
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20
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Queen C, Korn LJ. A comprehensive sequence analysis program for the IBM personal computer. Nucleic Acids Res 1984; 12:581-99. [PMID: 6546431 PMCID: PMC321072 DOI: 10.1093/nar/12.1part2.581] [Citation(s) in RCA: 512] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have developed a versatile program for the analysis of nucleic acid and protein sequences on the IBM Personal Computer. The program is interactive and self-instructing. It contains all the features generally found in sequence analysis programs on large computers, including extensive homology routines, as well as new procedures for the entry of sequence data. The program contains facilities to store and utilize the entire Nucleic Acid Sequence Data Bank. We have devised a new algorithm to find restriction enzyme sites, which allows our microcomputer program to find all sites on a small plasmid for 100 different enzymes in 1 to 2 minutes.
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21
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Mikelsaar R. Human mitochondrial genome and the evolution of methionine transfer ribonucleic acids. J Theor Biol 1984; 105:221-32. [PMID: 6558300 DOI: 10.1016/s0022-5193(83)80004-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The recently deciphered sequence of the human mitochondrial genome is analyzed in the light of an archigenetic hypothesis, according to which mitochondria are derived neither from pro- nor eukaryotes but from more primitive organisms. The possibility that animal mitochondria have only one gene both for elongator and initiator methionine tRNA is supported but C-A pair forming cytosine in the anticodon of these tRNAs is considered to be unmodified. The evolution of the gene and of the codon reading pattern of methionine tRNA is discussed.
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22
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Looney JE, Harding JD. Structure and evolution of a mouse tRNA gene cluster encoding tRNAAsp, tRNAGly and tRNAGlu and an unlinked, solitary gene encoding tRNAAsp. Nucleic Acids Res 1983; 11:8761-75. [PMID: 6324100 PMCID: PMC326622 DOI: 10.1093/nar/11.24.8761] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We have sequenced mouse tRNA genes from two recombinant lambda phage. An 1800 bp sequence from one phage contains 3 tRNA genes, potentially encoding tRNAAsp, tRNAGly, and tRNAGlu, separated by spacer sequences of 587 bp and 436 bp, respectively. The mouse tRNA gene cluster is homologous to a rat sequence (Sekiya et al., 1981, Nucleic Acids Res. 9, 2239-2250). The mouse and rat tRNAAsp and tRNAGly coding regions are identical. The tRNAGlu coding regions differ at two positions. The flanking sequences contain 3 non-homologous areas: a c. 100 bp insertion in the first mouse spacer, short tandemly repeated sequences in the second spacers and unrelated sequences at the 3' ends of the clusters. In contrast, most of the flanking regions are homologous, consisting of strings of consecutive, identical residues (5-17 bp) separated by single base differences and short insertions/deletions. The latter are often associated with short repeats. The homology of the flanking regions is c. 75%, similar to other murine genes. The second lambda clone contains a solitary mouse tRNAAsp gene. The coding region is identical to that of the clustered tRNAAsp gene. The 5' flanking regions of the two genes contain homologous areas (10-25 bp) separated by unrelated sequences. Overall, the flanking regions of the two mouse tRNAAsp genes are less homologous than those of the mouse and rat clusters.
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23
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Hatfield DL, Dudock BS, Eden FC. Characterization and nucleotide sequence of a chicken gene encoding an opal suppressor tRNA and its flanking DNA segments. Proc Natl Acad Sci U S A 1983; 80:4940-4. [PMID: 6308662 PMCID: PMC384163 DOI: 10.1073/pnas.80.16.4940] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
A naturally occurring opal suppressor serine tRNA has been purified from chicken liver and used as a probe to isolate the corresponding gene from a library of chicken DNA in bacteriophage lambda. This minor tRNA is encoded by a single-copy gene that is not part of a tRNA gene cluster. DNA sequence analysis of the gene and its flanking DNA segments shows that the gene is encoded in an 87-base-pair segment without intervening sequences and specifies a tRNA that reads the termination codon UGA. This gene has additional nucleotides in the 5' internal promoter region but has a normal 3' internal promoter sequence and the usual termination signal.
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24
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Naylor SL, Sakaguchi AY, Shows TB, Grzeschik KH, Holmes M, Zasloff M. Two nonallelic tRNAiMet genes are located in the p23 leads to q12 region of human chromosome 6. Proc Natl Acad Sci U S A 1983; 80:5027-31. [PMID: 6308668 PMCID: PMC384181 DOI: 10.1073/pnas.80.16.5027] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Two nonallelic human tRNAiMet genes were assigned to chromosome 6 by filter hybridization of DNA from human-rodent somatic cell hybrids by using probes containing unique sequences from the regions flanking each tRNAiMet gene. These unique sequence probes thus allowed each tRNAiMet gene to be analyzed individually in cell hybrids. Both tRNAiMet genes segregated in the hybrid cells with the chromosome 6 enzyme markers, soluble malic enzyme and the mitochondrial form of superoxide dismutase, and also with a karyotypically normal chromosome 6. By using hybrid clones containing translocations that divide chromosome 6 into five segments, both tRNAiMet genes were assigned to the p23 leads to q12 region. These results raise the possibility that other tRNAiMet genes may be syntenic with the two described in this study and illustrate the utility of using unique flanking sequences to identify members of a multigene family.
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25
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Hu JC, Cote BD, Lund E, Dahlberg JE. Isolation and characterization of genomic mouse DNA clones containing sequences homologous to tRNAs and 5S rRNA. Nucleic Acids Res 1983; 11:4809-21. [PMID: 6308561 PMCID: PMC326087 DOI: 10.1093/nar/11.14.4809] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We have cloned and characterized three fragments of Balb/c mouse DNA which hybridize to mouse cell tRNAs. Fractionation of the tRNAs which hybridize to these clones reveals that two of the clones, lambda Mt-4A and lambda Mt-6A hybridize to only one or two tRNAs, while one clone, lambda Mt-4B, hybridizes to at least seven tRNAs. Two of the tRNAs were identified as tRNAProCCG and tRNAGlyGGA, and others have been identified as tRNAs which are selectively encapsidated into virions of murine leukemia virus and avian reticuloendotheliosis virus. The DNA sequences of putative genes for tRNAProCCG and tRNAGlyGGA, plus flanking regions, were determined. A clone of Balb/c mouse DNA which selectively hybridized to 5S rRNA was also isolated and partially characterized.
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26
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Bawnik N, Beckmann JS, Sarid S, Daniel V. Isolation and nucleotide sequence of a plant tRNA gene: petunia asparagine tRNA. Nucleic Acids Res 1983; 11:1117-22. [PMID: 6298732 PMCID: PMC325779 DOI: 10.1093/nar/11.4.1117] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
A 14.3 kb petunia genomic DNA fragment was isolated and found to contain a single tRNA gene coding for asparagine tRNA. The nucleotide sequence of the asparagine tRNA gene and its flanking regions has been determined. This gene does not contain intervening sequences nor the 3'-end CCA sequence of the mature tRNA and presents a similar overall sequence homology (70%) to both E. coli and mammalian asparagine tRNA. As in other eukaryotic tRNA genes the 5'-flanking region does not seem to contain any special sequence that could function as a regulatory element and the 3'-end is followed by a short cluster of T that may function as the transcription termination site.
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27
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28
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Sharp S, Cooley L, DeFranco D, Dingermann T, Söll D. Organization and expression of tRNA genes in Drosophila melanogaster. Recent Results Cancer Res 1983; 84:1-14. [PMID: 6405456 DOI: 10.1007/978-3-642-81947-6_1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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29
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Tranquilla TA, Cortese R, Melton D, Smith JD. Sequences of four tRNA genes from Caenorhabditis elegans and the expression of C. elegans tRNALeu (anticodon IAG) in Xenopus oocytes. Nucleic Acids Res 1982; 10:7919-34. [PMID: 6761649 PMCID: PMC327059 DOI: 10.1093/nar/10.24.7919] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Four tRNA genes have been identified in cloned segments of Caenorhabditis elegans DNA by tRNA hybridisation and expression after injection into Xenopus laevis oocyte nuclei. From DNA sequencing these are (with DNA anticodon sequences) tRNAAsp (GTC), tRNALeu (AAG), tRNALys (CTT) and tRNAPro (TGG). Their flanking DNA sequences are compared. Two identical tRNALys (CTT) genes from different regions of the genome have quite unrelated 5' flanking sequences. The tRNA synthesised in Xenopus oocytes after injection of the tRNALeu cloned DNA has the modified anticodon IAG. The tRNALeu gene precursor transcript from injected oocytes has short 5' and 3' additional sequences and lacks certain of those modified bases found in the processed tRNA.
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30
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Reilly JG, Ogden R, Rossi JJ. Isolation of a mouse pseudo tRNA gene encoding CCA--a possible example of reverse flow of genetic information. Nature 1982; 300:287-9. [PMID: 6924072 DOI: 10.1038/300287a0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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31
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Cribbs DL, Gillam IC, Tener GM. The structure of tRNA 5 Lys from Drosophila melanogaster. Nucleic Acids Res 1982; 10:6393-9. [PMID: 6817300 PMCID: PMC326929 DOI: 10.1093/nar/10.20.6393] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The nucleotide sequence of Drosophila melanogaster tRNA 5 Lys is pGCCCGGAUAm2GCUCAGDCGGDAGAGCA psi psi GGACUsU*UUt6A*A psi CCAAGGm7GDm5CCAGGGTm psi CAm1AGUCCCUGUUCGGGCGCCA. The sU* is probably 5-methylcarboxymethyl-2-thiouridine and t6A* is a mixture of modified derivatives of t6A including t6A itself and a component sensitive to treatment with cyanogen bromide. This tRNA 5 Lys is 95% homologous to the rabbit liver tRNA 5 Lys.
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32
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DeFranco D, Burke KB, Hayashi S, Tener GM, Miller RC, Söll D. Genes for tRNALys5 from Drosophila melanogaster. Nucleic Acids Res 1982; 10:5799-808. [PMID: 6292853 PMCID: PMC320931 DOI: 10.1093/nar/10.19.5799] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The sequences of two cloned genes from Drosophila which hybridize with tRNALys5 are reported. One gene, in plasmid pDt39, has a sequence which corresponds to the sequence of tRNA. The other gene, in pDt59R, differs in three nucleotides pairs. Both plasmids are transcribed in vitro with extracts of Drosophila Kc cells to give full-sized tRNA precursors with four additional nucleotides at the 5'-end as well as truncated molecules containing 35 nucleotides. This premature termination occurs in a block of four T residues within the mature coding region. Sequences flanking the tRNA genes show little in common except for the blocks of five or more T-residues beyond the 3'-end of the gene. pDt39 hybridizes to 84AB on the polytene chromosomes of Drosophila and pDt59R hybridizes to 29A.
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33
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Abstract
We have sequenced a 1307 base pair mouse genomic DNA fragment which contains a histidine tRNA gene. The sequence of the putative mouse histidine tRNA differs from the published sequence of sheep liver histidine tRNA by a single base change in the D-loop. It does not contain an unpaired 5' terminal G residue, as reported for Drosophila and sheep histidine tRNAs. The gene does not contain introns. The 3' flanking region contains a typical RNA polymerase III termination site of 6 consecutive T residues. 523 residues after the 3' end of the his tRNA coding region, the mouse DNA contains a sequence 72% homologous to part of the consensus sequence of the B1 (alu) family.
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34
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Indik ZK, Tartof KD. Glutamate tRNA genes are adjacent to 5S RNA genes in Drosophila and reveal a conserved upstream sequence (the ACT-TA box). Nucleic Acids Res 1982; 10:4159-72. [PMID: 6289265 PMCID: PMC320790 DOI: 10.1093/nar/10.14.4159] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
In Drosophila melanogaster at least six transfer RNA genes are located adjacent to the 3' end of the 5S RNA gene cluster. Three of these have been sequenced and identified as coding for glutamate tRNA4. In the chromosome they are arranged as tandem repeats on the same DNA strand and transcribed in the same direction as is 5S DNA, towards the centromere. We have also identified a sequence, the ACT-TA box, that is highly conserved among the polymerase III transcribed genes. Usually the sequence is located at 37 +/- 8 base pairs upstream from the first nucleotide of the structural gene. A similar sequence is also observed upstream of yeast and silkworm tRNA genes and the mitochondrial tRNA genes of mouse and humans.
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35
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Zasloff M, Santos T, Romeo P, Rosenberg M. Transcription and precursor processing of normal and mutant human tRNAiMet genes in a homologous cell-free system. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)34461-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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36
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Larsen TM, Miller RC, Spiegelman GB, Hayashi S, Tener GM, Sinclair DA, Grigliatti TA. RNA-DNA hybridization analyses of tRNA-Val-3b in Drosophila melanogaster. MOLECULAR & GENERAL GENETICS : MGG 1982; 185:390-6. [PMID: 6808320 DOI: 10.1007/bf00334129] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Transfer RNA was extracted from 50-300 mg of adult flies and specifically labeled in vitro. The level of individual isoacceptors was quantitated by efficient annealing to Drosophila tRNA genes carried on recombinant DNA plasmids immobilized on nitrocellulose filters. The level of tRNAVal3b in the tRNA isolated from flies deficient in the major tRNAVal3b loci has been examined. The results show that deletion of the major tRNAVal3b loci resulted in a reduction of approximately 50% in the level of tRNAVal3b but did not produce the Minute phenotype; furthermore the effects of deficiencies at two loci were approximately additive.
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37
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Abstract
This paper is concerned with the basic question as to whether there exists a complex interaction between DNA sequences which have little specific function and functional genes regarding the spatial arrangement of the gene. Since gene clusters are a characteristic and basic feature of gene structure in higher eukaryotes, the size of extragenic DNA sequences surrounding the individual genes of various clustered gene families were compared. The size of the intergenic region, which is composed of the extragenic DNA sequences flanking the 3'-end of one gene and those flanking the 5'-end of the other gene, of the paired genes increases as the genes becomes larger. However, such a gene size-dependent increase is not seen if the total gene size of the paired genes is less than 0.3 kb or greater than 4 kb. The results suggests that a higher eukaryote gene requires extragenic territorial DNA sequences surrounding it, which presumably are necessary to maintain the gene's active functions.
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38
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Queen C, Wegman MN, Korn LJ. Improvements to a program for DNA analysis: a procedure to find homologies among many sequences. Nucleic Acids Res 1982; 10:449-56. [PMID: 6174938 PMCID: PMC326145 DOI: 10.1093/nar/10.1.449] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
We have devised an algorithm for finding partial homologies among a set of nucleotide sequences. The algorithm and other improvements have been incorporated into a commonly used computer program for the analysis of sequence data.
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39
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Addison W, Astell C, Delaney A, Gillam I, Hayashi S, Miller R, Rajput B, Smith M, Taylor D, Tener G. The structures of genes hybridizing with tRNA4Val from Drosophila melanogaster. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(19)68245-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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40
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41
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Will BM, Bayev AA, Finnegan DJ. Nucleotide sequence of terminal repeats of 412 transposable elements of Drosophila melanogaster. A similarity to proviral long terminal repeats and its implications for the mechanism of transposition. J Mol Biol 1981; 153:897-915. [PMID: 6283088 DOI: 10.1016/0022-2836(81)90458-7] [Citation(s) in RCA: 74] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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42
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DeFranco D, Sharp S, Söll D. Identification of regulatory sequences contained in the 5'-flanking region of Drosophila lysine tRNA2 genes. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(18)43290-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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43
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Lasser-Weiss M, Bawnik N, Rosen A, Sarid S, Daniel V. Isolation and characterization of cloned rat DNA fragment carrying tRNA genes. Nucleic Acids Res 1981; 9:5965-78. [PMID: 6273815 PMCID: PMC327577 DOI: 10.1093/nar/9.22.5965] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
A rat genomic library was screened for tRNA genes with an unfractionated rat liver tRNA probe. About 70 clones containing tRNA genes were detected per rat genome. The organization of tRNA genes in five clones was analyzed by restriction endonuclease digestion, RNA-DNA hybridization and in vitro transcription with nuclear extracts from Xenopus oocytes. Evidence is presented suggesting that tRNA genes are distributed in the rat genome in small clusters spanning 1 to 2 kb and interspersed with large regions (minimum 8 to 20 kb) of non tRNA-coding DNA. The tRNA gene clusters were found to contain the sequences for a variety of tRNA species. Genes for a single isoacceptor, were found in more than one clone. The detailed study of one clone shows the repetition of a cluster of four tRNA sequences at a distance of about 8 kb. The arrangement of tRNA genes in rat appears to follow the irregular pattern of tRNA gene organization previously reported in Drosophila and Xenopus.
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44
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Sharp S, DeFranco D, Silberklang M, Hosbach HA, Schmidt T, Kubli E, Gergen JP, Wensink PC, Söll D. The initiator tRNA genes of Drosophila melanogaster: evidence for a tRNA pseudogene. Nucleic Acids Res 1981; 9:5867-82. [PMID: 6273811 PMCID: PMC327570 DOI: 10.1093/nar/9.22.5867] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We have isolated four segments of Drosophila melanogaster DNA that hybridize to homologous initiator tRNAMet. Three of the cloned fragments contain initiator tRNA genes, each of which can be transcribed in vitro. The fourth clone, pPW568, contains an initiator tRNA pseudogene which is not transcribed in vitro by RNA polymerase III. The pseudogene is contained in a 1.15 kb DNA fragment. This fragment has the characteristics of dispersed repetitive DNA and hybridizes in situ to at least 30 sites in the Drosophila genome. The arrangement of the initiator tRNA genes we have isolated, is different to that of other Drosophila tRNA gene families. The initiator tRNA genes are not clustered nor intermingled with other tRNA genes. They occur as single copies within an approximately 415-bp repeat segment, which is separated from other initiator tRNA genes by a mean distance of 17 kb. In situ hybridization to polytene chromosomes localizes these genes to the 61D region of the Drosophila genome. Hybridization analysis of genomic DNA indicates the presence of 8-9 non-allelic initiator tRNA genes in Drosophila melanogaster.
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45
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Sharp S, DeFranco D, Dingermann T, Farrell P, Söll D. Internal control regions for transcription of eukaryotic tRNA genes. Proc Natl Acad Sci U S A 1981; 78:6657-61. [PMID: 6947245 PMCID: PMC349108 DOI: 10.1073/pnas.78.11.6657] [Citation(s) in RCA: 151] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
We have identified the region within a eukaryotic tRNA gene required for initiation of transcription. These results were obtained by systematically constructing deletions extending from the 5' or the 3' flanking regions into a cloned Drosophila tRNAArg gene by using nuclease BAL 31. The ability of the newly generated deletion clones to direct the in vitro synthesis of tRNA precursors was measured in transcription systems from Xenopus laevis oocytes, Drosophila Kc cells, and HeLa cells. Two control regions within the coding sequence were identified. The first was essential for transcription and was contained between nucleotides 8 and 25 of the mature tRNA sequence. Genes devoid of the second control region, which was contained between nucleotides 50 and 58 of the mature tRNA sequence, could be transcribed but with reduced efficiency. Thus, the promoter regions within a tRNA gene encode the tRNA sequences of the D stem and D loop, the invariant uridine at position 8, and the semi-invariant G-T-psi-C sequence.
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46
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Zhimulev IF, Belyaeva ES, Semeshin VF. Informational content of polytene chromosome bands and puffs. CRC CRITICAL REVIEWS IN BIOCHEMISTRY 1981; 11:303-40. [PMID: 6171381 DOI: 10.1080/10409238109104420] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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47
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Bona M, Scheer U, Bautz EK. Antibodies of RNA polymerase II (B) inhibit transcription in Lampbrush chromosomes after microinjection into living amphibian oocytes. J Mol Biol 1981; 151:81-99. [PMID: 7328655 DOI: 10.1016/0022-2836(81)90222-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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48
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Bauman JG, Wiegant J, Van Duijn P, Lubsen NH, Sondermeijer PJ, Hennig W, Kubli E. Rapid and high resolution detection of in situ hybridisation to polytene chromosomes using fluorochrome-labeled RNA. Chromosoma 1981; 84:1-18. [PMID: 6170491 DOI: 10.1007/bf00293359] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Fluorochrome-labeled RNA allows the rapid detection of in situ hybrids without the need for long exposure times as in the autoradiographical hybridisation methods. Resolution is high because of the high resolving power of fluorescence microscopy. The application of a previously reported method for the hybrido-cytochemical detection of DNA sequences to polytene chromosomes of Drosophilia is described. The specificity and sensitivity of the method are demonstrated by the hybridisation with polytene chromosomes of 1) rhodamine-labeled 5S RNA, to the 5S rRNA sites of D. melanogaster (56F) and D. hydei (23B), 2) rhodamine-labeled RNA complementary to a plasmid containing histone genes, to the 39DE region of D. melanogaster, 3) rhodamine-labeled D. melanogaster tRNA species (Gly-3 and Arg-2), to their respective loci in D. melanogaster, 4) rhodamine-labeled RNA complementary to the insert of plasmid 232.1 containing part of a D. melanogaster heat shock gene from locus 87C, to D. hydei heat shock locus 2-32A. In the latter instance it was possible to demonstrate the labeling of a double band which escaped unambiguous detection by autoradiography in the radioactive cytochemical hybridisation procedure because of the low topological resolution of autoradiograms. The sensitivity of the fluorochrome-labeled RNA method is compared with the radioactive methods which use 3H- or 125 I-labeled RNAs. The factors governing the sensitivity and the number of bound fluorochrome molecules to be expected are discussed.
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49
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Dudler R, Schmidt T, Bienz M, Kubli E. The genes coding for tRNA Tyr of Drosophila melanogaster: localization of determination of the gene numbers. Chromosoma 1981; 84:49-60. [PMID: 6794997 DOI: 10.1007/bf00293362] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Transfer RNA(Tyr) (anticodon G psi A) was isolated from Drosophila melanogaster by means of Sepharose 4B, RPC-5, and polyacrylamide gel electrophoresis. The rRNA was iodinated in vitro with Na125 I and hybridized in situ to salivary gland chromosomes from Drosophila. The genes of rRNA(Tyr) were localized in eight regions of the genome by autoradiography. Restriction enzyme analysis of genomic DNA indicated that the haploid Drosophila genome codes for about 23 tRNA(Tyr) genes. The regions 22F and 85A each contain four to five tRNA(Tyr) genes, whereas the regions 28C, 41AB, 42A, 42E, and 56D each contain two to three tRNA(Tyr) genes.
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50
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Abstract
Small nuclear RNAs were isolated from human placenta and fractionated into individual molecular species. They were then iodinated with 125I and used as probes to screen the human genome. Of 2 x 10(4) recombinant phage clones screened, 22 clones hybridized with U6 RNA, suggesting that there were about 200 copies of this sequence family per haploid genome. Southern blots of these cloned DNAs digested with several restriction enzymes gave the following results: 1, each clone had only one fragment that carried the U6 sequence, 2, the lengths of these fragments varied from clone to clone. These observations indicate that U6 sequences exist as dispersed middle repetitive DNA, and that the sequences surrounding these loci vary. Two of the loci and their flanking regions were subcloned into plasmid and sequenced. Both of the loci showed microheterogeneity of mainly A/G and T/C, but had closely related sequences to U6 RNAs of rat or mouse. The divergence of the flanking regions begins immediately outside the loci. The implication on the microheterogeneity of the U6-related sequences is discussed.
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