Structural heterogeneity and genomic distribution of Drosophila melanogaster LTR-retrotransposons
ABSTRACT Structural heterogeneity of five long terminal repeat (LTR) retrotransposon families (297, mdg 1, 412, copia, and 1731) was investigated in Drosophila melanogaster. The genomic distribution of canonical and rearranged elements was studied by comparing hybridization patterns of Southern blots on salivary glands from adult females and males with in situ hybridization on polytene chromosomes. The proportion and genomic distribution of noncanonical copies is distinctive to each family and presents constant features in the four different D. melanogaster strains studied. Most elements of families 297 and mdg 1 were noncanonical and presented large interstock and intrastock polymorphism. Noncanonical elements of these two families were mostly located in euchromatin, although not restricted to it. The elements of families 412 and copia were better conserved. The proportion of noncanonical elements was lower. The 1731 family is mainly composed of noncanonical, beta-heterochromatic elements that are highly conserved among stocks. The relation of structural polymorphism to phylogeny, transpositional activity and the role of natural selection in the maintenance of transposable elements are discussed.
Article: Argonaute protein PIWI controls mobilization of retrotransposons in the Drosophila male germline.[show abstract] [hide abstract]
ABSTRACT: Proteins of the Argonaute family have been identified as key components of RNA interference (RNAi) pathway. RNAi-related mechanisms are implicated in the regulation of gene expression and repression of transposable elements in eukaryotes. The piwi gene encoding protein of the Drosophila Argonaute family was shown to be required for the germ stem cells maintenance. Here, we show that piwi is involved in silencing of LTR retrotransposons in testes. piwi mutations led to derepression of endogenous retrotransposon copia as well as to upregulation of the reporter gene driven by copia LTR. piwi mutation causes accumulation of retrotransposon mdg1 transcripts at the apical tip of testes, including germinal proliferative center where PIWI protein was shown to be expressed. We applied inverse PCR approach to detect the newly arisen insertions of the mdg1 retrotransposon in the progeny of individual piwi mutant males. Owing to piwi mutation a high rate of mdg1 transpositions was revealed. Thus, piwi is involved in the silencing of retrotransposons in the precursors of male gametes. Our results provide the first evidence that protein of the Argonaute family prevents retrotranspositions. It is supposed that the disturbance of RNA silencing system in germinal cells might cause transposition burst.Nucleic Acids Research 02/2005; 33(6):2052-9. · 8.03 Impact Factor
Article: Mobile elements and genome evolution[show abstract] [hide abstract]
ABSTRACT: Mobile elements (MEs) are an important component of the genome in all eukaryotes and prokaryotes. MEs are divided into two large classes differing in the mechanism of transposition. Class I MEs are transposed via reverse transcription of their RNA transcripts. Class II MEs code for transposase, which acts at the DNA level and recognizes the ends of the cognate ME. The review considers the distribution of MEs from different classes in various genomes, individual chromosomes, and chromatin types. There is ample evidence for an important role of MEs in the regulation of cell genes and evolution of complex eukaryotic genomes. It is thought that ME invasion and subsequent amplification act as a main morphogenetic factor ensuring adaptation of populations to environmental changes and, in some cases, cause rapid speciation.Molecular Biology 03/2007; 41(2):203-213. · 0.66 Impact Factor