Feschotte Cédric, Osterlund Mark T, Peeler Ryan, Wessler Susan R
Department of Plant Biology, University of Georgia Athens, GA 30602, USA.
Nucleic Acids Res. 2005 Apr 14;33(7):2153-65. doi: 10.1093/nar/gki509. Print 2005.
Mariner-like elements (MLEs) are DNA transposons found throughout the plant and animal kingdoms. A previous computational survey of the rice (Oryza sativa) genome sequence revealed 34 full length MLEs (Osmars) belonging to 25 distinct families. This survey, which also identified sequence similarities between the Osmar elements and the Stowaway superfamily of MITEs, led to the formulation of a hypothesis whereby Stowaways are mobilized by OSMAR transposases. Here we investigate the DNA-binding activities and specificities of two OSMAR transposases, OSMAR5 and OSMAR10. Like other mariner-like transposases, the OSMARs bind specifically to the terminal inverted repeat (TIR) sequences of their encoding transposons. OSMAR5 binds DNA through a bipartite N-terminal domain containing two functionally separable helix-turn-helix motifs, resembling the paired domain of Tc1-like transposases and PAX transcription factors in metazoans. Furthermore, binding of the OSMARs is not limited to their own TIRs; OSMAR5 transposase can also interact in vitro with TIRs from closely related Osmar elements and with consensus TIRs of several Stowaway families mined from the rice genome sequence. These results provide the first biochemical evidence for a functional relationship between Osmar elements and Stowaway MITEs and lead us to suggest that there is extensive cross-talk among related but distinct transposon families co-existing in a single eukaryote genome.
类水手元件（MLEs）是在植物和动物界中都能找到的DNA转座子。先前对水稻（Oryza sativa）基因组序列的计算分析表明，有34个全长MLEs（Osmars）属于25个不同的家族。这项分析还确定了Osmar元件与MITEs的偷渡者超家族之间的序列相似性，从而形成了一个假说，即偷渡者是由OSMAR转座酶激活的。在这里，我们研究了两种OSMAR转座酶OSMAR5和OSMAR10的DNA结合活性和特异性。与其他类水手转座酶一样，OSMARs特异性地结合其编码转座子的末端反向重复（TIR）序列。OSMAR5通过一个二分的N端结构域结合DNA，该结构域包含两个功能上可分离的螺旋-转角-螺旋基序，类似于后生动物中Tc1样转座酶的配对结构域和PAX转录因子。此外，OSMARs的结合并不局限于它们自己的TIRs；OSMAR5转座酶在体外还可以与来自密切相关的Osmar元件的TIRs以及从水稻基因组序列中挖掘出的几个偷渡者家族的共有TIRs相互作用。这些结果为Osmar元件和偷渡者MITEs之间的功能关系提供了首个生化证据，并使我们认为，在单个真核生物基因组中共存的相关但不同的转座子家族之间存在广泛的相互作用。
