The putative transposase of transposable element Ac from Zea mays L. interacts with subterminal sequences of Ac.

Kunze, Reinhard; Starlinger, Peter

doi:10.1002/j.1460-2075.1989.tb08476.x

Cited by 168 publications

(148 citation statements)

References 50 publications

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“…The fact that a Ds element, which is almost identical in sequence to Ac, failed to yield mutations indicates that this is not the case, i.e., that slippage is not inherent to Ac sequence. It could be speculated that transposase induces slippage through binding to Ac sequences (27). No mutations were found with a stable transposase source.…”

Section: Discussionmentioning

confidence: 99%

Abortive Gap Repair: Underlying Mechanism for Ds element Formation

Rubin

Levy

1997

Molecular and Cellular Biology

114

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The mechanism by which the maize autonomous Ac transposable element gives rise to nonautonomous Ds elements is largely unknown. Sequence analysis of native maize Ds elements indicates a complex chimeric structure formed through deletions of Ac sequences with or without insertions of Ac-unrelated sequence blocks. These blocks are often flanked by short stretches of reshuffled and duplicated Ac sequences. To better understand the mechanism leading to Ds formation, we designed an assay for detecting alterations in Ac using transgenic tobacco plants carrying a single copy of Ac. We found frequent de novo alterations in Ac which were excision rather than sequence dependent, occurring within Ac but not within an almost identical Ds element and not within a stable transposase-producing gene. The de novo DNA rearrangements consisted of internal deletions with breakpoints usually occurring at short repeats and, in some cases, of duplication of Ac sequences or insertion of Ac-unrelated fragments. The ancient maize Ds elements and the young Ds elements in transgenic tobacco showed similar rearrangements, suggesting that Ac-Ds elements evolve rapidly, more so than stable genes, through deletions, duplications, and reshuffling of their own sequences and through capturing of unrelated sequences. The data presented here suggest that abortive Ac-induced gap repair, through the synthesis-dependent strand-annealing pathway, is the underlying mechanism for Ds element formation.Dissociation, or Ds, is the first discovered transposable element (TE). It was identified as a maize locus on chromosome 9, where breaks occur in the presence of Activator (Ac), a second gene found at a separate locus (33,34). Subsequent studies showed that Ac can transpose autonomously whereas Ds moves only in the presence of Ac (35,36). In addition, Ac activity can turn into a Ds type of instability, while no occurrences were found of Ds turning into Ac (37, 38). On the basis of these observations, McClintock proposed that Ds nonautonomous elements are derived from Ac through mutations (39). The proposal that Ac and Ds are phylogenetically related has been supported by molecular analysis, as described below, but the mechanism responsible for the conversion of Ac into Ds is still unknown.Ac is a 4.6-kb-long element flanked by 11-bp terminal inverted repeats (TIRs) (12). It encodes an 807-amino-acid protein, the transposase, necessary for both Ac and Ds transposition (28). Ds elements, on the other hand, do not encode a functional transposase but retain regions which are essential for their transposition (6). There are six fully sequenced Ds elements, all of which share with Ac nearly identical TIRs and fall into the following four categories: (i) those with nearly no similarity to Ac, like Ds1 (57); (ii) elements with highly similar subterminal regions but with internal deletions, like Ds9 (46); (iii) double Ds elements where one internally deleted Ds is inserted into another identical Ds in an inverted orientation (9); and (iv) Ds elements that contain bot...

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Section: Discussionmentioning

confidence: 99%

Abortive Gap Repair: Underlying Mechanism for Ds element Formation

Rubin

Levy

1997

Molecular and Cellular Biology

114

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“…Eukaryotic transposable elements that transpose via a DNA intermediate create short target site duplications upon insertion into a new site, contain short TIRs, and often contain near their termini short direct repeats that serve as transposase binding sites (Gierl et al, 1988;Kunze and Starlinger, 1989;Gierl and Saedler, 1992). Because the 1.6-kb insertion element has all of these properties, in addition to the demonstrated ability to be inserted into and excised out of the nitA locus, it would appear to be a transposon belonging to the class of elements such extended pair of inverted repeats is found near the right terminus nor anywhere else in the element.…”

Section: Sequence Characteristics Of the Elementmentioning

confidence: 99%

Jordan, an active Volvox transposable element similar to higher plant transposons.

1993

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We have isolated a 1595-bp transposable element from the multicellular green alga Volvox carteri following its insertion into the nitrate reductase (nitA) locus. This element, which we have named Jordan, has short (12-bp) terminal inverted repeats and creates a 3-bp target site duplication, like some higher plant transposons of the classic type. Contained within the first 200 bp of one end of the element are 55-bp inverted repeats, one of which begins with the terminal inverted repeat. Revertants of the transposon insertion into the nitA locus were obtained at a rate of . u~O -~ per Volvox embryo per generation. In each revertant examined, all transposon sequences were completely excised, but footprints containing both sets of duplicated bases, in addition to three to nine extra bases, were left behind. Jordan contains no significant open reading frames and so appean to be nonautonomous. DNA gel blot analysis indicates that Jordan is a member of a large family of homologous elements in the Volvox genome. We have isolated and characterized several of these homologs and found that they contain termini very similar to those of Jordan. Efforts to utilize Jordan and its homologs as tools to tag and clone developmentally interesting genes of Volvox are discussed.

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“…This ORF encodes a single, 807-amino acid protein, which is referred to as the Ac transposase (TPase), and is the sole element-encoded factor required for Ac transposition. Ac TPase catalyses the process of Ac transposition by specifically interacting with well defined cis-acting sequences near the termini of the element and there, presumably in conjunction with host-encoded factors, carrying out the necessary DNA modifications (Coupland et aL, 1988(Coupland et aL, , 1989Kunze and Starlinger, 1989). Dissociation, or Ds, elements are nonautonomous members of the family that lack the ability to encode TPase (through diverse, internal sequence modifications), but retain the cis-acting sequences necessary for transposition (DSring et aL, 1984;Sutton et aL, 1984).…”

Section: Introductionmentioning

confidence: 99%

Increased Ac excision (iae): Arabidopsis thaliana mutations affecting Ac transposition

Jarvis

Belzile

Page³

et al. 1997

The Plant Journal

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SummaryThe maize transposable element Ac is highly active in the heterologous hosts tobacco and tomato, but shows very much reduced levels of activity in Arabidopsis. A mutagenesis experiment was undertaken with the aim of identifying Arabidopsis host factors responsible for the observed low levels of Ac activity. Seed from a line carrying a single copy of the Ac element inserted into the streptomycin phosphotransferase (SPT) reporter fusion, and which displayed typically low levels of Ac activity, were mutagenized using gamma rays. Nineteen mutants displaying high levels of somatic Ac activity, as judged by their highly variegated phenotypes, were isolated after screening the M 2 generation on streptomycin-containing medium. The mutations fall into two complementation groups, iael and iae2, are unlinked to the SPT::Ac locus and segregate in a Mendelian fashion. The iael mutation is recessive and the iae2 mutation is semi-dominant. The iaeland iae2 mutants show 550-and 70-fold increases, respectively, in the average number of Ac excision sectors per cotyledon. The IAE1 locus maps to chromosome 2, whereas the SPT::Ac reporter maps to chromosome 3. A molecular study of Ac activity in the iael mutant confirmed the very high levels of Ac excision predicted using the phenotypic assay, but revealed only low levels of Ac re-insertion. Analyses of germinal transposition in the iael mutant demonstrated an average germinal excision frequency of 3% and a frequency of independent Ac re-insertions following germinal excision of 22%. The iae mutants represent a possible means of improving the efficiency of Ac/Ds transposon tagging systems in Arabidopsis, and will enable the dissection of host involvement in Ac transposition and the mechanisms employed for controlling transposable element activity.

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The putative transposase of transposable element Ac from Zea mays L. interacts with subterminal sequences of Ac.

Cited by 168 publications

References 50 publications

Abortive Gap Repair: Underlying Mechanism for Ds element Formation

Abortive Gap Repair: Underlying Mechanism for Ds element Formation

Jordan, an active Volvox transposable element similar to higher plant transposons.

Increased Ac excision (iae): Arabidopsis thaliana mutations affecting Ac transposition

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