Maxwell Patrick H, Belote John M, Levis Robert W
Department of Biology, Syracuse University, 130 College Place, Syracuse, NY 13244, USA.
Nucleic Acids Res. 2006;34(19):5498-507. doi: 10.1093/nar/gkl709. Epub 2006 Oct 4.
The Drosophila non-long terminal repeat (non-LTR) retrotransposons TART and HeT-A specifically retrotranspose to chromosome ends to maintain Drosophila telomeric DNA. Relatively little is known, though, about the regulation of their expression and their retrotransposition to telomeres. We have used rapid amplification of cDNA ends (RACE) to identify multiple transcription initiation and polyadenylation sites for sense and antisense transcripts of three subfamilies of TART elements in Drosophila melanogaster. These results are consistent with the production of an array of TART transcripts. In contrast to other Drosophila non-LTR elements, a major initiation site for sense transcripts was mapped near the 3' end of the TART 5'-untranslated region (5'-UTR), rather than at the start of the 5'-UTR. A sequence overlapping this sense start site contains a good match to an initiator consensus for the transcription start sites of Drosophila LTR retrotransposons. Interestingly, analysis of 5' RACE products for antisense transcripts and the GenBank EST database revealed that TART antisense transcripts contain multiple introns. Our results highlight differences between transcription of TART and of other Drosophila non-LTR elements and they provide a foundation for testing the relationship between exceptional aspects of TART transcription and TART's specialized role at telomeres.
果蝇非长末端重复（non-LTR）逆转录转座子TART和HeT-A专门逆转录转座到染色体末端以维持果蝇的端粒DNA。然而，关于它们的表达调控以及它们向端粒的逆转录转座，人们所知相对较少。我们利用cDNA末端快速扩增（RACE）技术，鉴定了黑腹果蝇中TART元件三个亚家族的正义和反义转录本的多个转录起始位点和聚腺苷酸化位点。这些结果与一系列TART转录本的产生一致。与其他果蝇非LTR元件不同，正义转录本的一个主要起始位点位于TART 5'非翻译区（5'-UTR）的3'端附近，而不是在5'-UTR的起始处。与这个正义起始位点重叠的一个序列与果蝇LTR逆转录转座子转录起始位点的起始子共有序列有很好的匹配。有趣的是，对反义转录本的5'RACE产物和GenBank EST数据库的分析表明，TART反义转录本包含多个内含子。我们的结果突出了TART转录与其他果蝇非LTR元件转录之间的差异，并为测试TART转录的特殊方面与TART在端粒的特殊作用之间的关系提供了基础。
