Pathania Shailja, Jayaram Makkuni, Harshey Rasika M
Section of Molecular Genetics and Microbiology and Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
EMBO J. 2003 Jul 15;22(14):3725-36. doi: 10.1093/emboj/cdg354.
Assembly of the Mu transpososome is dependent on interactions of transposase subunits with the left (L) and right (R) ends of Mu and an enhancer (E). We have followed the order and dynamics of association of these sites within a series of transpososomes prior to and during formation of a three-site complex (LER), engagement of Mu ends by the transposase active site (type 0 complex), cleavage of the ends (type I complex) and their transfer to target DNA (type II complex). LER appears to be preceded by a two-site complex (ER) where E and R are interwrapped twice, as in the mature transpososome. At each stage thereafter, the overall topology of five DNA supercoils is retained: two between E and R, one between E and L and two between L and R. However, L-R interactions within LER appear to be flexible. Unexpectedly, the enhancer was seen to persist within the transpososome through cleavage and strand transfer of Mu ends to target DNA.
Mu转座体的组装依赖于转座酶亚基与Mu的左端（L）和右端（R）以及一个增强子（E）之间的相互作用。我们追踪了在形成三位点复合物（LER）之前和期间、转座酶活性位点与Mu末端结合（0型复合物）、末端切割（I型复合物）以及它们转移到靶DNA（II型复合物）的一系列转座体内这些位点的结合顺序和动力学。LER似乎之前存在一个两位点复合物（ER），其中E和R像在成熟转座体中一样相互缠绕两次。此后在每个阶段，五个DNA超螺旋的整体拓扑结构得以保留：E和R之间有两个，E和L之间有一个，L和R之间有两个。然而，LER内的L-R相互作用似乎是灵活的。出乎意料的是，在Mu末端切割并链转移到靶DNA的过程中，增强子仍持续存在于转座体内。
