Structure and function of novel prokaryotic DNA transposases

我们最近开始了多药耐药细菌中插入序列运动的研究，重点是产碳青霉烯酶的肠杆菌（CPE）。转座因子通常与抗生素耐药性决定因素有关，表明在耐药性的出现中起作用。据报道，一个插入序列IS26经常与耐药决定因子相关，但其作用尚不清楚。我们分析了来自NIH临床中心的几个临床和监测CPE分离株的70个IS26拷贝的基因组背景。我们以靶位重复（TSDs）及其分布模式为指导，发现大部分质粒重组是由IS26分子内复制转位引起的，包括复制子融合、DNA倒位和缺失。我们现在已经将这些研究扩展到其他类型的移动元素。我们也有兴趣从其活性移动元件的角度跟踪携带多药耐药决定因子的质粒的持续重组。

We have recently initiated an investigation of Insertion Sequence movements in multi drug resistant bacteria with a focus on carbapenemase-producing Enterobacteriacaea (CPE). Transposable elements are often associated with antibiotic resistance determinants, suggesting a role in the emergence of resistance. One insertion sequence, IS26, has been reported to be frequently associated with resistance determinants, but its role remained unclear. We have analyzed the genomic contexts of 70 IS26 copies in several clinical and surveillance CPE isolates from the NIH Clinical Center. We used target site duplications (TSDs) and their distribution patterns as guides and discovered that a large fraction of plasmid reorganizations result from IS26 intramolecular replicative transpositions, including replicon fusions, DNA inversions, and deletions. We have now extended these studies to other types of mobile elements. We are also interested in following the ongoing reorganization of plasmids carrying multidrug-resistant determinants from the perspective of their active mobile elements. More recently,resistance even for colistin, which is a "last resort" antibiotics have been observed to emerge in enterobacteriaceae. We have discovered that dissemination of the colistin resistance gene appears linked to a particular mobile genetic element, and we are in the process of its characterization. One prokaryotic transposition mechanism that clearly plays a central role in the emergence of multi antibiotic resistance is the so-call copy-out-paste-in mechanism. Despite its central importance, there is no current mechanistic information available regarding how this process works. Recently, we have identified a mobile genetic element called IS256 that uses this process and we have been able to generate crystals of the IS256 family transposase complexed with DNA that diffracts X-rays well. Crystallographic structure determination is underway. Curcio, M.J. and Derbyshire, K.M. (2003) Nat. Rev. Mol. Cell. Biol. 4, 865-877. Debets-Ossenkopp, Y.J., et al. (1999) Antimicrob. Agents Chemother. 43, 2657-2662. Sebaihia, M. et al. (2006) Nature Genet. 38, 779-786.