Close relationship between the long terminal repeats of avian leukosis-sarcoma virus and copia-like movable genetic elements of Drosophila.

Kugimiya, Wataru; Ikenaga, Hiroshi; Saigo, Kaoru

doi:10.1073/pnas.80.11.3193

Cited by 62 publications

(21 citation statements)

References 27 publications

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“…Distribution of copy numbers of transposable elements, P, 297, and copia between lines of Akayu population in D. melanogaster genome since some transposons such as 17.6 and 297 have target-sequencespecificity (Ikenaga and Saigo 1983;Inouye et al 1984) . However, the nonrandomness of the inserted sites is not so conspicuous since more than 105 ( _ 1.6 X 108/44) target sites are expected to be present in a genome.…”

Section: Resultsmentioning

confidence: 99%

“…Among them are copia, 297 and P elements which are studied in this report. copia and 297 are 5.0 kb and 7.2 kb in length with about 400 by long terminal repeats (LTRs), respectively (Rubin 1983;Kugimiya et al 1983). Both copia and 297 are copia-like elements which are known to be intimately related in evolution to retroviruses in vertebrates and suggested to transpose via RNA intermediates Saigo et al 1984;Arkcipova et al 1984;Flavell 1984).…”

Section: Introductionmentioning

confidence: 99%

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Distributions of three transposable elements, P, 297, and copia, in natural populations of Drosophila melanogaster.

Yamaguchi

Yamazaki

Saigo

et al. 1987

The Japanese journal of genetics

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Two Japanese natural populations and a Canary Island cage population of Drosophila melanogaster were analyzed with respect to three transposable elements P, 297, and copia, using chromosomal in situ hybridization, copia was distributed more or less equally over all chromosomes. Its copy number on the X chromosome was slightly less than that on autosomes of equivalent size, possibly indicating the near neutrality or slightly deleteriousness of the transposable element actually present in the chromosomes. The distribution of P elements was a little different from that of the other two transposable elements, as it was not concentrated around chromocenter, in contrast to that of 297 and copia. No evidence of threshold was observed with respect to the copy number of transposable elements in a genome in any of the three transposable elements. The variance of copy number of these transposons between different strains were generally larger than those expected under the poisson distribution, especially in the P element. These observations possibly indicate near neutrality of these transposable elements (in their present positions) with respect to natural selection or non-equilibrium state in populations.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Distributions of three transposable elements, P, 297, and copia, in natural populations of Drosophila melanogaster.

Yamaguchi

Yamazaki

Saigo

et al. 1987

The Japanese journal of genetics

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“…Many investigators have suggested that the eucaryotic transposable elements which are structurally similar to the proviral forms of vertebrate retroviruses might transpose via RNA intermediates (13,14,27,49). A reverse transcription mode of transposition of IAP elements is supported by the fact that all new insertions of these elements have been discovered in IAP-producing cells (for review see reference 16).…”

Section: __________________---_--------------------------------------mentioning

confidence: 99%

Transposition of two different intracisternal A particle elements into an immunoglobulin kappa-chain gene.

Hawley¹,

Shulman²,

Hozumi³

1984

Mol. Cell. Biol.

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Each of two severely defective mouse K-chain genes has acquired a different intracisternal A particle (IAP) element within one of its introns. One IAP element generated 6-base-pair direct repeats upon insertion. In contrast, the other IAP element was not flanked by direct repeats and was missing a single nucleotide from its 3' terminus. Sequence analysis of the latter IAP element demonstrated that its long terminal repeats were not identical. Nevertheless, the long terminal repeats were organized like proviral long terminal repeats, and this IAP element did contain two regions that were analogous to retroviral priming sites for RNA-directed DNA synthesis. The region that corresponded to a retroviral tRNA primer binding site was complementary to the 3' ends of all mammalian phenylalanine tRNAs. These findings are discussed in the context of the presumed mode of transposition of IAP elements involving the reverse transcription of LAP RNA.Transposable elements were first genetically identified in maize by McClintock because of their ability to affect gene expression and induce a multitude of chromosomal aberrations (34). Subsequently, transposable elements have been found in a variety of procaryotic and eucaryotic organisms (for reviews see reference 45), and it is now assumed that they are ubiquitous.Intracisternal A particles (IAPs) are retrovirus-like entities that are present in many embryonic and transformed cells of Mus musculus (3,4,7,12,57). Similar to retroviruses, IAPs contain a high-molecular-weight RNA species (30, 38) and a reverse transcriptase-like activity (56,59). However, unlike retroviruses, IAPs have no known extracellular phase (12,36). Approximately 1,000 DNA sequences homologous to IAP RNA (IAP elements) are scattered throughout the mouse genome (28,29). Like many of the repeated sequences in lower eucaryotes (41, 42), mouse IAP elements have a gross structural organization similar to that of the proviral forms of vertebrate retroviruses (10,26,54). Recently, transpositions of IAP elements have been observed in several transformed mouse cells (6, 9, 48) and in some cell lines derived from them (17). Because the cells in which the transpositions occurred contain IAPs, a reverse transcription mode of transposition of IAP elements is suggested.We first discovered the transposition of IAP sequences during the analysis of two mutant mouse hybridoma cell lines that were selected on the basis of defective expression of their immunoglobulin kappa (K)-chain genes (24). Characterization of molecular clones of portions of the K-chain genes from these mutant hybridomas revealed that each gene contained IAP sequences within one of its introns (17). We cloned the regions spanning both of these loci. Different IAP elements have inserted into the two K-chain genes. Here we present the nucleotide sequences at the junctions of both insertion sites and at the termini of one IAP element. These studies demonstrate that, although IAP elements resemble retroviral proviruses in many respects, they differ from provir...

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“…A major question posed by the observed bidirectional transcription of the solo TED LTR is whether the same (23,38) and copia (9,29), the S. cerevisiae retrotransposon Ty912 (5,8), and the retrovirus human Tlymphotropic virus type III/lymphadenopathy virus (30,39,42,48). …”

Section: Effectsmentioning

confidence: 99%

Bidirectional transcription from a solo long terminal repeat of the retrotransposon TED: symmetrical RNA start sites.

Friesen¹,

Rice²,

Miller³

et al. 1986

Mol. Cell. Biol.

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A single copy of the retrotransposon TED was found integrated within the DNA genome of the insect baculovirus, Autographa californica nuclear polyhedrosis virus. After excision of the element from the viral genome, a single long terminal repeat (LTR) remained behind. We have examined the effect of this solo TED LTR on the local pattern of viral transcription. Most prominent was the transcription of two sets of abundant RNAs; both originated within the LTR but extended in opposite directions into flanking viral genes. By promoting symmetric transcription of adjacent genes, the solo LTR has the capacity to activate or repress gene expression in two directions. Primer extension analysis demonstrated that the divergent LTR transcripts were initiated near the same point within a 22-base-pair sequence having hyphenated twofold symmetry. Analogous symmetries at the initiation sites of other retrotransposon LTRs, including copia and Ty, suggested that these sequences serve to establish the precise start for transcription.The retrotransposons represent a group of eucaryotic transposable elements which bear a striking resemblance to the retroviral proviruses (for review, see reference 1). These elements, which include copia and copia-related transposons of Drosophila melanogaster and Ty of Saccharomyces cerevisiae, are flanked at both ends by long terminal repeats (LTRs). The LTRs carry signals necessary for initiation and termination of transcription. The transcribed internal portion of these elements contains several retroviruslike genes, including a gene (pol) with homology to reverse transcriptase (5, 9, 29, 38). In the case of Ty, the full-length RNA extending, from LTR to LTR is copied into DNA by a process identical to that of the retroviruses, suggesting that transposition occurs through reverse transcription of an RNA intermediate (3).By virtue of their ability to integrate randomly into the host genome and alter expression of nearby genes, the retroviruses represent an important class of insertion mutagens (for review, see reference 44). Similarly, the retrotransposons cause insertion mutations in D. melanogaster and S. cerevisiae (reviews in references 35 and 37). Integration within regulatory regions or introns of various genes has resulted in enhancement or inhibition of expression. These alterations occur at the level of transcription and are presumably due to insertion of new promoters, termination signals, or both, located within the retrotransposon. The mutagenic effects of inserted copia, gypsy, and Ty elements are suppressed by additional mutations at unlinked loci which restore transcription of the affected genes to wild-type levels (25,32,51). Mutation of the S. cerevisiae SPT3 (suppressor of Ty) gene, for instance, abolishes normal Ty transcription, which suggests that the mutational effect of certain Ty insertions is due to transcription originating from the element (51). The exact mechanisms involved are still unclear.TED is the first copia-related transposable element iden-

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Close relationship between the long terminal repeats of avian leukosis-sarcoma virus and copia-like movable genetic elements of Drosophila.

Cited by 62 publications

References 27 publications

Distributions of three transposable elements, P, 297, and copia, in natural populations of Drosophila melanogaster.

Distributions of three transposable elements, P, 297, and copia, in natural populations of Drosophila melanogaster.

Transposition of two different intracisternal A particle elements into an immunoglobulin kappa-chain gene.

Bidirectional transcription from a solo long terminal repeat of the retrotransposon TED: symmetrical RNA start sites.

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