Onstead Jonathan, Zhang Zhongge, Huo Jialu, Ord Jack W, Smith Sofia, Saier Milton H
Department of Molecular Biology, School of Biological Sciences, University of California at San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0116, USA.
Microorganisms. 2024 Dec 16;12(12):2600. doi: 10.3390/microorganisms12122600.
Insertions of the transposable element IS5 into its target sites in response to stressful environmental conditions, DNA structures, and DNA-binding proteins are well studied, but how the genomic contexts near IS5's native loci impact its transpositions is largely unknown. Here, by examining the roles of all 11 copies of IS5 within the genome of strain BW25113 in transposition, we reveal that the most significant copy of IS5 is one nested within and oriented in the same direction as the gene, while two other copies of IS5 harboring point mutations are hardly transposed. Transposition activity is heavily reliant on the upstream promoter that drives IS5 transposase gene , with more transpositions resulting from greater promoter activity. The IS5 element at but not at other loci transcribed detectable amounts of mRNA. By increasing expression of the operon harbored in IS5, we demonstrate that Ins5B and Ins5C appear to exert a stimulatory role in IS5 transposition, suggesting that the downstream genomic regions near the native loci are involved in overall IS5 transposition as well. Using a strain that carries IS5 only at the locus, we confirm that IS5 primarily uses a copy/paste mechanism for transposition, although we cannot rule out the cut/paste mechanism.
转座元件IS5在应激环境条件、DNA结构和DNA结合蛋白作用下插入其靶位点的过程已得到充分研究，但IS5天然位点附近的基因组背景如何影响其转座在很大程度上尚不清楚。在这里，通过研究BW25113菌株基因组中11个IS5拷贝在转座中的作用，我们发现IS5最主要的拷贝是嵌套在基因内且与该基因同向的一个拷贝，而另外两个携带点突变的IS5拷贝几乎不发生转座。转座活性严重依赖于驱动IS5转座酶基因的上游启动子，启动子活性越高，转座事件越多。位于特定位置而非其他位点的IS5元件转录出可检测量的mRNA。通过增加IS5中携带的操纵子的表达，我们证明Ins5B和Ins5C似乎在IS5转座中发挥刺激作用，这表明天然位点附近的下游基因组区域也参与了IS5的整体转座。使用仅在特定位置携带IS5的菌株，我们证实IS5主要使用复制/粘贴机制进行转座，尽管我们不能排除剪切/粘贴机制。
