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At least 163 records · Page 9Linked to original sources
PubMed2005

Allopolyploidy in wheat induces rapid and heritable alterations in DNA methylation patterns of cellular genes and mobile elements.

Whereas accumulating recent evidences indicate that allopolyploid formation in plants is accompanied by rapid and non-Mendelian genomic changes, some other works showed genomic stasis in both nascent and natural allopolyploids. To further study the issue, we performed global DNA fingerprinting of a newly synthesized allohexaploid wheat and its natural counterpart, the common wheat, by AFLP analysis. It was found that ca. 20% bands showed deviation from parental additivity in both synthetic and the natural common wheat. Sequence analysis indicates that a majority of the changed bands represent known-function genes and transposable elements. DNA gel blot analysis showed that the main type of changes in the amphiploid is epigenetic in nature, i.e., alteration in DNA methylation patterns. Two types of alterations in methylation, random and non-random, were detected, and both types were stably inherited. Possible causes and implications of the epigenetic changes in allopolyploid genome evolution and speciation are discussed.

DNA Methylation↗
PubMed1990

[Transcription of Drosophila MDG4 mobile element under hyperthermic conditions].

The Drosophila melanogaster cultured cells were subjected to stable transformation by cotransfection with two plasmids, one of which conferred G418 resistance and the second contained the Drosophila retrotransposon MDG4 (gypsy) under control of different promoter fragments of the heat shock protein gene hsp70. Transcription of these constructs as well as of the endogenous gypsy was examined in the conditions of heat shock. Active degradation of preexisting MDG4 transcripts is observed after heat shock. Transcription of MDG4 is restored during recovery but its termination and/or 3' end processing becomes aberrant.

Animals↗
PubMed1990

[Mobile element RSBP1 of Bordetella pertussis].

A number of repeated sequences was identified in the chromosome of Bordetella pertussis by the electron microscopic analysis of the chromosomal DNA of this microorganism. One of the sequences was cloned on the vector plasmid pHC79. It is shown to consist of two elements RSBP1 and RSBP2. The first elements is probably identical to an RS-element described previously. The cloned RSBP1 element is shown to stimulate the deletion formation in the genome of the plasmid pMKII and is able to transpose into the chromosome of Escherichia coli. The latter properties permit one to classify RSBP1 as an element belonging to a class of migrating genetical elements.

Bordetella pertussis↗
PubMed1988

[The Drosophila mobile element jockey, being a typical LINE, is transcribed from the internal promoter by RNA polymerase II].

Two polyadenylated transcripts of the jockey are detected at different stages of Drosophila melanogaster ontogenesis and in the cell culture. They have the same length as complete and deleted copies of jockey and correspond to the DNA strand containing open reading frames coding for polypeptides which are homologous to retroviral RNA-(DNA)-binding proteins and to their reverse transcriptases. The results of the experiments, where transcription was inhibited with alpha-amanitin in vivo, indicate that jockey is transcribed by RNA polymerase II. The analysis of expression of CAT constructions made on the basis of jockey, and the detection of a fixed site for transcription initiation in jockey genomic and transfected copies have shown that jockey transcription is controlled by an internal promoter located not farther than 12 nucleotides from the beginning of the element. Such an inward location of the promoter allows it to be preserved in replication via reverse transcription and accounts for the distribution of jockey and probably other LINEs throughout the genome. This is the case of the first internal promoter described for RNA polymerase II. The comparison of starting sequences of LINEs in Drosophila makes it possible to detect core sequences of such a promoter.

Amanitins↗
PubMedDate not supplied

[The coevolutionary aspects of the genome and mobile elements].

Under investigation is congruent variation of movable elements, the "genome parasites" (GP), and genome proper, as the "host". Several differential equations are studied that describe the following situations. 1. GP is able to insert in free sites only, existing in autonomous stage (outside of the genome) limited time only. 2. GP inserts in free sites only, being able to exist autonomously relatively long time. 3. GP inserts in both free and occupied sites ("molecular memory"), existing autonomously relatively short time, its prototype being Alu-like repetitions in mammals. 4. GP inserts in both free and occupied sites, and is able to live autonomously, its prototype being retrovirus. In is presumed that the genome is tolerant to "selfish" breeding of GP as long as proportion of invaded sites does not exceed some critical value. It is shown that co-evolutionary complication of GP--from the simplest one that is able to insert in free sites only, through acquiring terminal repetitions ("molecular memory"), up to complicated entities existing outside of genome--accompanied by alteration of selective co-evolutionary limitations on genome size: limitations from above--no limitations--limitations from below. Thus, genetical movable elements can be considered as intrinsic factor of progressive, co-evolutionary stipulated complication of the genome.

Animals↗
PubMedDate not supplied

[Long terminal repeats of drosophila mobile elements direct transcript ion in Escherichia coli cells].

Retrotransposons of D. melanogaster are similar to vertebrate retroviruses in their structure and function. Long terminal repeats (LTR) of retrotransposons contain specific eukaryotic promoters and transcriptional control sequences. Recently it has been shown that several retroviral LTRs contain in addition some promoter-like sequences that are functional in E. coli cells. Plasmid constructions containing the mdg1 and mdg4 LTR fragments and the standard reporter chloramphenicol acetyltransferase (cat) gene are also able to direct transcription and expression of the reporter cat gene in E. coli cells. Analysis of the primary structure of corresponding LTR fragments revealed sequences similar to conserved nucleotides of the putative prokaryotic promoter.

Animals↗
PubMed1993

[Mobile element distribution and quantitative character penetrance in the scute mutants of Drosophila melanogaster induced in the system of P-M hybrid dysgenesis].

A series of new scute mutants noted for reduction in one pair of bristles (humerals), but different penetrance with respect to this character, were induced in the system of P--M hybrid dysgenesis. In situ hybridization technique was used to determine the sites of the MEs pertaining to six families in 6 scute mutants and 18 isogenic lined derived from those. Through calculating the similarity indices, similarity with respect to the pattern of total distribution of all MEs examined was estimated for the lines. Results obtained favour the correlation between penetrance and ME localization. The "ME pattern-penetrance" dependence was verified using the isogenic lines. The matrix of similarity indices and the similarity tree were constructed for the mutant lines following comparative analysis of distribution of 132 hybridization sites. The structure of the tree gives in a number (3-4) of blocks made up by isogenic lines of different origin. The rank of stocks following merely ordering them as regards penetrance and the structure of both the tree and the matrix run together pretty well; what's more, compact blocks of labelled sites answer to the groups of stocks of close penetrance. Our results suggest that penetrance with respect to the number of numerals should directly depend on the peculiarities of ME localization in the genomes of mutant lines.

Alleles↗