Evolution of diverse mechanisms for protecting chromosome ends by the Drosophila TART telomere retrotransposons
Name
George-2010-Evolution of diverse mechanisms for protecting chromosome ends by Drosophila TART telomere retrotransposons.pdf
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Author(s)
George, Janet A.
Traverse, Karen L.
Kelley, Kerry
Pardue, Mary-Lou
DeBaryshe, P. G.
Date Issued
November 2010
Journal
Proceedings of the National Academy of Sciences of the United States of America
Publisher
National Academy of Sciences (U.S.)
Citation
George, Janet A. et al. “Evolution of Diverse Mechanisms for Protecting Chromosome Ends by Drosophila TART Telomere Retrotransposons.” Proceedings of the National Academy of Sciences 107.49 (2010) : 21052 -21057. ©2010 by the National Academy of Sciences
Version
Final published version
Abstract
The retrotransposons HeT-A, TART, and TAHRE, which maintain Drosophila telomeres, transpose specifically onto chromosome ends to form long arrays that extend the chromosome and compensate for terminal loss. Because they transpose by target-primed reverse transcription, each element is oriented so that its 5′ end serves as the extreme end of the chromosome until another element transposes to occupy the terminal position. Thus 5′ sequences are at risk for terminal erosion while the element is at the chromosome end. Here we report that TART elements in Drosophila melanogaster and Drosophila virilis show species-specific innovations in promoter architecture that buffer loss of sequence exposed at chromosome ends. The two elements have evolved different ways to effect this protection. The D. virilis TART (TARTvir) promoter is found in the 3′ UTR of the element directly upstream of the element transcribed. Transcription starts within the upstream element so that a “Tag” of extra sequence is added to the 5′ end of the newly transcribed RNA. This Tag provides expendable sequence to buffer end erosion of essential 5′ sequence after the RNA is reverse transcribed onto the chromosome. In contrast, the D. melanogaster TART (TARTmel) promoter initiates transcription deep within the 5′ UTR, but the element is able to replace and extend the 5′ UTR sequence by copying sequence from its 3′ UTR, we believe while being reverse transcribed onto the chromosome end. Astonishingly, end-protection in TARTvir and HeT-Amel are essentially identical (using Tags), whereas HeT-Avir is clearly protected from end erosion by an as-yet-unspecified program.
MIT Department
Massachusetts Institute of Technology. Department of Biology
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DOI of Published Version
https://doi.org/10.1073/pnas.1015926107
