title: Losing helena: the extinction of a drosophila line-like element.
abstract: BACKGROUND
  Transposable elements (TEs) are major players in evolution. We know that they play an essential role in genome size determination, but we still have an incomplete understanding of the processes involved in their amplification and elimination from genomes and populations. Taking advantage of differences in the amount and distribution of the Long Interspersed Nuclear Element (LINE), helena in Drosophila melanogaster and D. simulans, we analyzed the DNA sequences of copies of this element in samples of various natural populations of these two species.
  
  
  RESULTS
  In situ hybridization experiments revealed that helena is absent from the chromosome arms of D. melanogaster, while it is present in the chromosome arms of D. simulans, which is an unusual feature for a TE in these species. Molecular analyses showed that the helena sequences detected in D. melanogaster were all deleted copies, which diverged from the canonical element. Natural populations of D. simulans have several copies, a few of them full-length, but most of them internally deleted.
  
  
  CONCLUSIONS
  Overall, our data suggest that a mechanism that induces internal deletions in the helena sequences is active in the D. simulans genome.
authors: Université de Lyon; Université Lyon 1; CNRS; UMR 5558, Laboratoire de Biométrie et Biologie Evolutive, Villeurbanne F-69622, France. rebollo@biomserv.univ-lyon1.fr
authors: Rita
authors: R
authors: Rebollo
authors: Emmanuelle
authors: E
authors: Lerat
authors: Liliana Lopez
authors: LL
authors: Kleine
authors: Christian
authors: C
authors: Biémont
authors: Cristina
authors: C
authors: Vieira
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D004251:DNA Transposable Elements / Q000235:genetics*; D004330:Drosophila / Q000235:genetics*; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D017403:In Situ Hybridization; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D004251:DNA Transposable Elements