Howard Hughes Medical Institute, Cambridge, MA 02139, USA; Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD 20894, USA.
Mol Cell. 2023 Jun 15;83(12):2122-2136.e10. doi: 10.1016/j.molcel.2023.05.013. Epub 2023 Jun 1.
To spread, transposons must integrate into target sites without disruption of essential genes while avoiding host defense systems. Tn7-like transposons employ multiple mechanisms for target-site selection, including protein-guided targeting and, in CRISPR-associated transposons (CASTs), RNA-guided targeting. Combining phylogenomic and structural analyses, we conducted a broad survey of target selectors, revealing diverse mechanisms used by Tn7 to recognize target sites, including previously uncharacterized target-selector proteins found in newly discovered transposable elements (TEs). We experimentally characterized a CAST I-D system and a Tn6022-like transposon that uses TnsF, which contains an inactivated tyrosine recombinase domain, to target the comM gene. Additionally, we identified a non-Tn7 transposon, Tsy, encoding a homolog of TnsF with an active tyrosine recombinase domain, which we show also inserts into comM. Our findings show that Tn7 transposons employ modular architecture and co-opt target selectors from various sources to optimize target selection and drive transposon spread.
转座子要扩散，必须在不干扰必需基因的情况下整合到靶位，同时避免宿主防御系统。Tn7 样转座子采用多种机制进行靶位选择，包括蛋白指导的靶向和 CRISPR 相关转座子 (CASTs)中的 RNA 指导的靶向。通过系统发育基因组学和结构分析，我们对靶位选择器进行了广泛的调查，揭示了 Tn7 用于识别靶位的各种机制，包括在新发现的可移动元件 (TEs)中发现的以前未表征的靶位选择器蛋白。我们通过实验对 CAST I-D 系统和 Tn6022 样转座子进行了表征，该转座子使用含有失活酪氨酸重组酶结构域的 TnsF 靶向 comM 基因。此外，我们还鉴定了一个非 Tn7 转座子 Tsy，它编码一个具有活性酪氨酸重组酶结构域的 TnsF 同源物，我们还发现它也插入到 comM 中。我们的研究结果表明，Tn7 转座子采用模块化架构，并从各种来源中选择靶位选择器，以优化靶位选择并推动转座子的扩散。
