Coevolution of the telomeric retrotransposons across Drosophila species.
As in other eukaryotes, telomeres in Drosophila melanogaster are composed of long arrays of repeated DNA sequences. Remarkably, in D. melanogaster these repeats are produced, not by telomerase, but by successive transpositions of two telomere-specific retrotransposons, HeT-A and TART. These are the only transposable elements known to be completely dedicated to a role in chromosomes, a finding that provides an opportunity for investigating questions about the evolution of telomeres, telomerase, and the transposable elements themselves. Recent studies of D. yakuba revealed the presence of HeT-A elements with precisely the same unusual characteristics as HeT-A(mel) although they had only 55% nucleotide sequence identity. We now report that the second element, TART, is also a telomere component in D. yakuba; thus, these two elements have been evolving together since before the separation of the melanogaster and yakuba species complexes. Like HeT-A(yak), TART(yak) is undergoing concerted sequence evolution, yet they retain the unusual features TART(mel) shares with HeT-A(mel). There are at least two subfamilies of TART(yak) with significantly different sequence and expression. Surprisingly, one subfamily of TART(yak) has >95% sequence identity with a subfamily of TART(mel) and shows similar transcription patterns. As in D. melanogaster, other retrotransposons are excluded from the D. yakuba terminal arrays studied to date.
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Elena
E
Casacuberta
Mary-Lou
ML
Pardue
D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D017931:DNA Primers; D004330:Drosophila / Q000145:classification / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics; D019143:Evolution, Molecular; D008297:Male; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D012194:RNA-Directed DNA Polymerase; D012091:Repetitive Sequences, Nucleic Acid; D018626:Retroelements / Q000235:genetics*; D016615:Telomere / Q000235:genetics; D014998:Y Chromosome / Q000235:genetics
D017931:DNA Primers; D029721:Drosophila Proteins; D018626:Retroelements; C469435:TART-element-gag protein, Drosophila; D004247:DNA; D012194:RNA-Directed DNA Polymerase