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Sequenze Omologhe all’Elemento Trasponibile Minos di Drosophila hydei nel Genoma di Drosophila melanogaster e di Altre Specie del genere Drosophila.
No full textDistribution of the transposable element Minos in the genus Drosophila
No full textWe analyzed 28 species or the genus Drosophila for the presence of the Tc1-like transposable element Minos using Southern blot hybridization under high stringency conditions. The Minos transposon was found in members of both the Drosophila and the Sophophora subgenus showing a distribution that is wider if compared to other well-studied Drosophila transposons such as the P element, hobo and mariner. The presence of Mines-hybridizing sequences was discontinuous in the Sophophora subgenus, especially in the melanogaster species group. Using the Polymerase Chain Reaction we amplified a portion corresponding to the putative Mines transposase from different Drosophila species. Cloning and sequence analysis of randomly selected Mines copies from D. mojavensisis, D. saltans and D. willistoni supports the idea that event(s) of horizontal transfer may have contributed to the spreading of this transposon in the Drosophila genus
Mobilization of a Minos transposon in Drosophila melanogaster chromosomes and chromatid repair by heteroduplex formation.
No full textTransposase-mediated mobilization of the element Minos has been studied in the Drosophila melanogaster genome. Excision and transposition of a nonautonomous Minos transposon in the presence of a Minos transposase gene was detected with a dominant eye color marker carried by the transposon. Frequencies of excision in somatic tissues and in the germ line were higher in flies heterozygous for the transposon than in homozygotes or hemizygotes. Transposition of a X chromosome-linked insertion of Minos into new autosomal sites occurred in 1-12% of males expressing transposase, suggesting that this system is usable for gene tagging and enhancer trapping in Drosophila. Sequence analysis of PCR-amplified donor sites after excision showed precise restoration of the original target sequence in approximately 75% of events in heterozygotes and the presence of footprints or partially deleted elements in the remaining events. Most footprints consisted of the four terminal bases of the transposon, flanked by the TA target duplication. Sequencing of a chromosomal donor site that was directly cloned after excision showed a characteristic two-base mismatch heteroduplex in the center of the 6-bp footprint. Circular extrachromosomal forms of the transposon, presumably representing excised Minos elements, could be detected only in the presence of transposase. A model for chromatid repair after Minos excision is discussed in which staggered cuts are first produced at the ends of the inverted repeats, the broken chromatid ends are joined, and the resulting heteroduplex is subsequently repaired. The model also suggests a simple mechanism for the production of the target site duplication and for regeneration of the transposon ends during reintegration
The Drosophila alcohol dehydrogenase gene may have evolved independently of the functionally homologous medfly, olive fly and flesh fly genes
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