Leem Young-Eun, Ripmaster Tracy L, Kelly Felice D, Ebina Hirotaka, Heincelman Marc E, Zhang Ke, Grewal Shiv I S, Hoffman Charles S, Levin Henry L
Section on Eukaryotic Transposable Elements, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Mol Cell. 2008 Apr 11;30(1):98-107. doi: 10.1016/j.molcel.2008.02.016.
The LTR-retrotransposon Tf1 preserves the coding capacity of its host Schizosaccharomyces pombe by integrating upstream of open reading frames (ORFs). To determine which features of the target sites were recognized by the transposon, we introduced plasmids containing candidate insertion sites into S. pombe and mapped the positions of integration. We found that Tf1 was targeted specifically to the promoters of Pol II-transcribed genes. A detailed analysis of integration in plasmids that contained either ade6 or fbp1 revealed insertions occurred in the promoters at positions where transcription factors bound. Further experiments revealed that the activator Atf1p and its binding site were required for directing integration to the promoter of fbp1. An interaction between Tf1 integrase and Atf1p was observed, indicating that integration at fbp1 was mediated by the activator bound to its promoter. Surprisingly, we found Tf1 contained sequences that activated transcription, and these substituted for elements of the ade6 promoter disrupted by integration.
LTR逆转座子Tf1通过整合到开放阅读框（ORF）上游来保留其宿主粟酒裂殖酵母的编码能力。为了确定转座子识别的靶位点特征，我们将含有候选插入位点的质粒导入粟酒裂殖酵母中，并绘制整合位置图。我们发现Tf1特异性靶向Pol II转录基因的启动子。对含有ade6或fbp1的质粒中的整合进行详细分析发现，插入发生在转录因子结合位置的启动子中。进一步实验表明，激活因子Atf1p及其结合位点是将整合导向fbp1启动子所必需的。观察到Tf1整合酶与Atf1p之间存在相互作用，表明在fbp1处的整合是由与其启动子结合的激活因子介导的。令人惊讶的是，我们发现Tf1含有激活转录的序列，并且这些序列替代了因整合而破坏的ade6启动子元件。
