Redd Priscilla S, Diaz Stephanie, Weidner David, Benjamin Jazmine, Hancock C Nathan
Department of Biology and Geology, University of South Carolina Aiken, Aiken, SC, 29801, USA.
Present address: Bayer Pharmaceuticals, Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA.
Mob DNA. 2023 Feb 11;14(1):1. doi: 10.1186/s13100-023-00289-3.
DNA transposable elements are mobilized by a "cut and paste" mechanism catalyzed by the binding of one or more transposase proteins to terminal inverted repeats (TIRs) to form a transpositional complex. Study of the rice genome indicates that the mPing element has experienced a recent burst in transposition compared to the closely related Ping and Pong elements. A previously developed yeast transposition assay allowed us to probe the role of both internal and terminal sequences in the mobilization of these elements.
We observed that mPing and a synthetic mPong element have significantly higher transposition efficiency than the related autonomous Ping and Pong elements. Systematic mutation of the internal sequences of both mPing and mPong identified multiple regions that promote or inhibit transposition. Simultaneous alteration of single bases on both mPing TIRs resulted in a significant reduction in transposition frequency, indicating that each base plays a role in efficient transposase binding. Testing chimeric mPing and mPong elements verified the important role of both the TIRs and internal regulatory regions. Previous experiments showed that the G at position 16, adjacent to the 5' TIR, allows mPing to have higher mobility. Alteration of the 16th and 17th base from mPing's 3' end or replacement of the 3' end with Pong 3' sequences significantly increased transposition frequency.
As the transposase proteins were consistent throughout this study, we conclude that the observed transposition differences are due to the element sequences. The presence of sub-optimal internal regions and TIR bases supports a model in which transposable elements self-limit their activity to prevent host damage and detection by host regulatory mechanisms. Knowing the role of the TIRs, adjacent sub-TIRs, and internal regulatory sequences allows for the creation of hyperactive elements.
DNA转座元件通过一种“剪切粘贴”机制进行移动，该机制由一个或多个转座酶蛋白与末端反向重复序列（TIR）结合催化形成转座复合体。对水稻基因组的研究表明，与密切相关的Ping和Pong元件相比，mPing元件最近经历了转座爆发。先前开发的酵母转座试验使我们能够探究内部和末端序列在这些元件移动中的作用。
我们观察到，mPing和一个合成的mPong元件的转座效率明显高于相关的自主Ping和Pong元件。对mPing和mPong内部序列进行系统突变，确定了多个促进或抑制转座的区域。同时改变mPing TIRs上的单个碱基会导致转座频率显著降低，表明每个碱基在转座酶有效结合中都发挥作用。测试嵌合的mPing和mPong元件证实了TIRs和内部调控区域的重要作用。先前的实验表明，与5'TIR相邻的第16位的G使mPing具有更高的移动性。改变mPing 3'端的第16和17位碱基或用Pong 3'序列替换3'端会显著提高转座频率。
由于在本研究中转座酶蛋白是一致的，我们得出结论，观察到的转座差异是由于元件序列造成的。次优内部区域和TIR碱基的存在支持了一种模型，即转座元件自我限制其活性以防止宿主损伤和被宿主调控机制检测到。了解TIRs、相邻的亚TIRs和内部调控序列的作用有助于创建高活性元件。
