Structure of the Drosophila HeT-A transposon: a retrotransposon-like element forming telomeres.
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 approximately 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.
Danilevskaya
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O
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Slot
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F
Pavlova
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Pardue
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ML
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002474:Cell-Free System; D016384:Consensus Sequence; D004331:Drosophila melanogaster / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D018626:Retroelements / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D016615:Telomere / Q000235:genetics*; D014158:Transcription, Genetic
D012333:RNA, Messenger; D018626:Retroelements