Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Cell. 2014 Jul 17;158(2):353-367. doi: 10.1016/j.cell.2014.05.037.
Hermes is a member of the hAT transposon superfamily that has active representatives, including McClintock's archetypal Ac mobile genetic element, in many eukaryotic species. The crystal structure of the Hermes transposase-DNA complex reveals that Hermes forms an octameric ring organized as a tetramer of dimers. Although isolated dimers are active in vitro for all the chemical steps of transposition, only octamers are active in vivo. The octamer can provide not only multiple specific DNA-binding domains to recognize repeated subterminal sequences within the transposon ends, which are important for activity, but also multiple nonspecific DNA binding surfaces for target capture. The unusual assembly explains the basis of bipartite DNA recognition at hAT transposon ends, provides a rationale for transposon end asymmetry, and suggests how the avidity provided by multiple sites of interaction could allow a transposase to locate its transposon ends amidst a sea of chromosomal DNA.
Hermes 是 hAT 转座子超家族的成员，该超家族在许多真核生物物种中都有活跃的代表，包括 McClintock 的典型 Ac 移动遗传元件。Hermes 转座酶-DNA 复合物的晶体结构表明，Hermes 形成一个八聚体环，组织为二聚体的四聚体。尽管分离的二聚体在体外对转座的所有化学步骤都具有活性，但只有八聚体在体内具有活性。八聚体不仅可以提供多个特异性 DNA 结合域来识别转座子末端内的重复亚末端序列，这对于活性很重要，而且还可以提供多个非特异性 DNA 结合表面来进行靶标捕获。这种不寻常的组装解释了 hAT 转座子末端二分体 DNA 识别的基础，为转座子末端的不对称性提供了依据，并表明了多个相互作用位点提供的亲和力如何使转座酶能够在染色体 DNA 的海洋中定位其转座子末端。
