Article

Chromosome Research

, Volume 13, Issue 5, pp 443-453

Two retrotransposons maintain telomeres in Drosophila

  • M.-L. PardueAffiliated withDepartment of Biology, Massachusetts Institute of Technology Email author 
  • , S. RashkovaAffiliated withDepartment of Biology, Massachusetts Institute of Technology
  • , E. CasacubertaAffiliated withDepartment of Biology, Massachusetts Institute of Technology
  • , P. G. DeBarysheAffiliated withDepartment of Biology, Massachusetts Institute of Technology
  • , J. A. GeorgeAffiliated withDepartment of Biology, Massachusetts Institute of Technology
  • , K. L. TraverseAffiliated withDepartment of Biology, Massachusetts Institute of Technology

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Abstract

Telomeres across the genus Drosophila are maintained, not by telomerase, but by two non-LTR retrotransposons, HeT-A and TART, that transpose specifically to chromosome ends. Successive transpositions result in long head-to-tail arrays of these elements. Thus Drosophila telomeres, like those produced by telomerase, consist of repeated sequences reverse transcribed from RNA templates. The Drosophila repeats, complete and 5′-truncated copies of HeT-A and TART, are more complex than telomerase repeats; nevertheless, these evolutionary variants have functional similarities to the more common telomeres. Like other telomeres, the Drosophila arrays are dynamic, fluctuating around an average length that can be changed by changes in the genetic background. Several proteins that interact with telomeres in other species have been found to have homologues that interact with Drosophila telomeres. Although they have hallmarks of non-LTR retrotransposons, HeT-A and TART appear to have a special relationship to Drosophila. Their Gag proteins are efficiently transported into diploid nuclei where HeT-A Gag recruits TART Gag to chromosome ends. Gags of other non-LTR elements remain predominantly in the cytoplasm. These studies provide intriguing evolutionary links between telomeres and retrotransposable elements.

Key words

chromosome evolution Gag protein nuclear localization retrotransposon telomere