Principal Investigator Mary-Lou Pardue
Although HeT-A, TART, and TAHRE are non-LTR retrotransposons, they also have distinctive features. Among these, we found that the HeT-A promoter in D. melanogaster resembles an evolutionary intermediate between promoters of LTR and non-LTR retrotransposons. The HeT-A promoter lies at the 3´ end of the element and promotes transcription of the adjacent downstream element, if it too is HeT-A, rather than the element in which it resides. Thus, the HeT-A promoter region is identical to the 3´ end of the element it promotes. Therefore, D. melanogaster HeT-A could be considered a pseudo-LTR element because its promoter is analogous to the LTR promoter. (LTRs have identical 5’- and 3’ends with the promoter in the 5’ end.) TART in the distantly related D. virilis has a similar promoter. In contrast, D. melanogaster TART and D. virilis HeT-A each have promoters typical of non-LTR elements. These promoters are in the 5’UTR (untranslated region) of the element, immediately downstream of the transcription start site so that the promoter is included in the RNA transposed to the new site.