Integration of transposable elements into the genome is mutagenic. Mechanisms targeting integrations into relatively safe locations, hence minimizing deleterious consequences for cell fitness, have emerged during evolution. In budding yeast, integration of the Ty1 LTR retrotransposon upstream of RNA polymerase III (Pol III)‐transcribed genes requires interaction between Ty1 integrase (IN1) and AC40, a subunit common to Pol I and Pol III. Here, we identify the Ty1 targeting domain of IN1 that ensures (i) IN1 binding to Pol I and Pol III through AC40, (ii) IN1 genome‐wide recruitment to Pol I‐ and Pol III‐transcribed genes, and (iii) Ty1 integration only at Pol III‐transcribed genes, while IN1 recruitment by AC40 is insufficient to target Ty1 integration into Pol I‐transcribed genes. Swapping the targeting domains between Ty5 and Ty1 integrases causes Ty5 integration at Pol III‐transcribed genes, indicating that the targeting domain of IN1 alone confers Ty1 integration site specificity.

中文翻译：

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Ty1整合酶中的一个小的靶向结构域足以指导逆转录转座子整合到tRNA基因的上游。

转座因子整合入基因组是诱变的。在进化过程中出现了针对整合到相对安全的位置，从而将对细胞适应性的有害影响降至最低的机制。在发芽酵母中，整合RNA聚合酶III（Pol III）转录基因上游的Ty1 LTR反转录转座子需要Ty1整合酶（IN1）和AC40（Pol I和Pol III共有的亚基）之间的相互作用。在这里，我们确定了IN1的Ty1靶向域，该域确保（i）IN1通过AC40与Pol I和Pol III结合，（ii）在IN1全基因组范围内募集到Pol I和Pol III转录的基因，以及（iii）Ty1整合仅在Pol III转录的基因上进行，而AC40募集的IN1不足以将Ty1整合到Pol I转录的基因上。