Search results for "Elements"
showing 10 items of 799 documents
Retrotransposon silencing and telomere integrity in somatic cells of Drosophila depends on the cytosine-5 methyltransferase DNMT2
2009
Here we show that the cytosine-5 methyltransferase DNMT2 controls retrotransposon silencing in Drosophila somatic cells. In Drosophila, significant DNMT2-dependent DNA methylation occurs during early embryogenesis. Suppression of white gene silencing by Mt2 (Dnmt2) null mutations in variegated P[w(+)] element insertions identified functional targets of DNMT2. The enzyme controls DNA methylation at retrotransposons in early embryos and initiates histone H4K20 trimethylation catalyzed by the SUV4-20 methyltransferase. In somatic cells, loss of DNMT2 eliminates H4K20 trimethylation at retrotransposons and impairs maintenance of retrotransposon silencing. In Dnmt2 and Suv4-20 null genotypes, re…
Structural and evolutionary analysis of the copia-like elements in the Arabidopsis thaliana genome.
2001
The analysis of 460 kb of genomic sequence of Arabidopsis thaliana chromosome III allowed us to identify two new transposable elements named AtC1 and AtC2. AtC1 shows identical long terminal repeats (LTRs) and all the structural features characteristic of the copia-like active elements. AtC2 is also a full copia-like element, but a putative stop codon in the open reading frame (ORF) would produce a truncated protein. In order to identify the copia-like fraction of the A. thaliana genome, a careful computer-based analysis of the available sequences (which correspond to 92% of the genome) was performed. Approximately 300 nonredundant copia-like sequences homologous to AtC1 and AtC2 were detec…
Invasion of thehobo transposable element studied byin situ hybridization on polytene chromosomes ofDrosophila melanogaster
1994
The invasion kinetics of hobo transposable element in the Drosophila melanogaster genome was studied by in situ hybridization on the polytene chromosomes. Six independent lines of Drosophila melanogaster flies that had been previously transformed by microinjection of the pHFL1 plasmid containing a complete hobo element were followed over 50 generations. We observed that hobo elements were scattered on each of the chromosome arms, with more insertion sites on the 3R arm. The total number of insertion sites remains quite small, between four and six, at generation 52. On the 2R arm, a short inversion appeared once at generation 52. Most of the integration sites reported here were already descr…
GyDB mobilomics: LTR retroelements and integrase-related transposons of the pea aphid Acyrthosiphon pisum genome
2011
[EN] The Gypsy Database concerning Mobile Genetic Elements (release 2.0) is a wiki-style project devoted to the phylogenetic classification of LTR retroelements and their viral and host gene relatives characterized from distinct organisms. Furthermore, GyDB 2.0 is concerned with studying mobile elements within genomes. Therefore, an in-progress repository was created for databases with annotations of mobile genetic elements from particular genomes. This repository is called Mobilomics and the first uploaded database contains 549 LTR retroelements and related transposases which have been annotated from the genome of the Pea aphid Acyrthosiphon pisum. Mobilomics is accessible from the GyDB 2.…
Chromatin structure of transposon Tn903 cloned into a yeast plasmid
1989
Transposon Tn903 contains the APH gene for kanamycin resistance, which is active in yeast [A. Jiménez and J. Davies (1980) Nature (London) 287, 869-871] and is flanked by two inverted repeats (IR) 1057 bp long. When plasmid pAJ50, carrying Tn903 and the 2-microns circle origin of replication, is cloned into Saccharomyces cerevisiae, nucleosomes are assembled in vivo on the prokaryotic DNA of the transposon. Indirect end labeling revealed that three nucleosomes are preferentially positioned on symmetrical sequences from both IRs. DNase I digestion also confirmed that the chromatin structure is symmetrical in both IRs. This suggests that sequence determinants are decisive for chromatin struct…
The Norway spruce genome sequence and conifer genome evolution
2013
Conifers have dominated forests for more than 200 million years and are of huge ecological and economic importance. Here we present the draft assembly of the 20-gigabase genome of Norway spruce (Picea abies), the first available for any gymnosperm. The number of well-supported genes (28,354) is similar to the >100 times smaller genome of Arabidopsis thaliana, and there is no evidence of a recent whole-genome duplication in the gymnosperm lineage. Instead, the large genome size seems to result from the slow and steady accumulation of a diverse set of long-terminal repeat transposable elements, possibly owing to the lack of an efficient elimination mechanism. Comparative sequencing of Pinu…
Structure and expression of clustered P element homologues in Drosophila subobscura and Drosophila guanche
1995
Abstract Sequence relationships and functional aspects were analysed in the P element homologues of Drosophila subobscura (Ds) and D. guanche (Dg) . In both species, the P homologues are clustered at a single genomic position. They lack the characteristic terminal structures of actively transposing P elements, but they have the coding capacity for a 66-kDa ‘repressor-like’ protein. Two different types of cluster units (G-type and A-type) can be distinguished. The A-type unit, which is present in multiple copies, is transcribed in adult flies. In contrast, the G-type unit has a much lower copy number and is apparently not expressed. In Dg , the isolated G-type sequence carries a 420-bp inser…
PGal4 excision reveals the pleiotropic effects of Voila, a Drosophila locus that affects development and courtship behaviour
2001
0016-6723 (Print) Journal Article Research Support, Non-U.S. Gov't; In Drosophila melanogaster, the PGal4 transposon inserted at the chromosomal site 86E1-2 is associated with the Voila1 allele that causes multiple phenotypes. Homozygous Voila1/1 flies rarely reach adulthood and heterozygous Voila1/+ adult males display strong homosexual courtship behaviour. Both normal behavioural and developmental phenotypes were rescued by remobilizing the PGal4 element. Yet, the rescue of heterosexual courtship and of adult viability did not occur in the same strains, indicating that these defects have different genetic origins. Furthermore, many strains showed a partial rescue of both characters. Molec…
The sex determining region of Chironomus thummi is associated with highly repetitive DNA and transposable elements.
1993
The dominant male sex determiner in chromosome III of the midge Chironomus thummi thummi is closely linked to a large cluster of tandem-repetitive DNA elements, the Cla elements, which are otherwise highly repetitive and distributed over more than 200 sites on all chromosomes. Chromosome III displays a hemizygous cluster of Cla elements in males but not in females. The chromosomal location of this hemizygous Cla element cluster is in the region of the male determiner M as localized by cytogenetic analysis. With Cla elements as hybridization probe, it was possible to clone a large part of the sex determining region. Molecular analysis of the DNA of males and females in this region displayed …
Spread of the autonomous transposable element hobo in the genome of Drosophila melanogaster.
1995
The transposable element hobo has been introduced into the previously empty Drosophila melanogaster strain Hikone so that its dynamics can be followed and it can be compared with the P element. Five transformed lines were followed over 58 generations. The results were highly dependent on the culture temperature, the spread of hobo element being more efficient at 25 degrees C. The multiplication of hobo sequences resulted in a change in the features of these lines in the hobo system of hybrid dysgenesis. The number of hobo elements remained low (two to seven copies) and the insertions always corresponded to complete sequences. Our findings suggest that, despite their genetic similarities, P …