Abstract
Telomeres of Drosophila appear to be very different from those of other organisms. A transposable element, HeT-A, plays a major role in forming telomeres and may be the sole structural element, since telomerase-generated repeats are not found. HeT-A transposes only to chromosome ends. It appears to be a retrotransposon but has novel structural features, which may be related to its telomere functions. A consensus sequence from cloned HeT-A elements defines an element of ∼6 kb. The coding region has retrotransposon-like overlapping open reading frames (ORFs) with a −1 frameshift in a sequence resembling the frameshift region of the mammalian HIV-1 retrovirus. Both the HeT-A ORFs contain motifs suggesting RNA binding. HeT-A-specific features include a long non-coding region, 3′ of the ORFs, which makes up about half of the element. This region has a regular array of imperfect sequence repeats and ends with oligo(A), marking the end of the element and suggesting a polyadenylated RNA transposition intermediate. This 3′ repeat region may have a structural role in heterochromatin. The most distal part of each complete HeT-A on the chromosome, the region 5′ of the ORFs, has unusual conserved features, which might produce a terminal structure for the chromosome.
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Danilevskaya, O., Slot, F., Pavlova, M. et al. Structure of the Drosophila HeT-A transposon: a retrotransposon-like element forming telomeres. Chromosoma 103, 215–224 (1994). https://doi.org/10.1007/BF00368015
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DOI: https://doi.org/10.1007/BF00368015