Richardson Julia M, Colloms Sean D, Finnegan David J, Walkinshaw Malcolm D
School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland.
Cell. 2009 Sep 18;138(6):1096-108. doi: 10.1016/j.cell.2009.07.012.
A key step in cut-and-paste DNA transposition is the pairing of transposon ends before the element is excised and inserted at a new site in its host genome. Crystallographic analyses of the paired-end complex (PEC) formed from precleaved transposon ends and the transposase of the eukaryotic element Mos1 reveals two parallel ends bound to a dimeric enzyme. The complex has a trans arrangement, with each transposon end recognized by the DNA binding region of one transposase monomer and by the active site of the other monomer. Two additional DNA duplexes in the crystal indicate likely binding sites for flanking DNA. Biochemical data provide support for a model of the target capture complex and identify Arg186 to be critical for target binding. Mixing experiments indicate that a transposase dimer initiates first-strand cleavage and suggest a pathway for PEC formation.
在DNA转座的剪切粘贴过程中，一个关键步骤是在转座子元件从宿主基因组中切除并插入新位点之前，使转座子末端配对。对由预先切割的转座子末端和真核元件Mos1的转座酶形成的配对末端复合物（PEC）进行的晶体学分析表明，两个平行的末端与二聚体酶结合。该复合物呈反式排列，每个转座子末端由一个转座酶单体的DNA结合区域和另一个单体的活性位点识别。晶体中的另外两条DNA双链表明了侧翼DNA的可能结合位点。生化数据为目标捕获复合物模型提供了支持，并确定精氨酸186对目标结合至关重要。混合实验表明转座酶二聚体启动了第一链切割，并提出了PEC形成的途径。
