Sawers R Gary
Department of Molecular Microbiology, John Innes Centre, Norwich NR4 7UH, United Kingdom.
FEMS Microbiol Lett. 2005 Mar 15;244(2):397-401. doi: 10.1016/j.femsle.2005.02.019.
The mobile insertion element IS5 is a relatively small but genetically compact DNA sequence of 1195bp found in variable copy number in the genome of Escherichia coli strains. This study presents a detailed transcript analysis of the population of IS5 elements present in E. coli strains MC4100 and MG1655. The findings indicate that the ins5A gene comprising 978bp is transcribed from its own promoter, which is located close to the right-hand end of the element. The two divergently transcribed genes ins5C and in5B form an operon, and this transcript is fully contained within the borders of the ins5A transcript. Although transcription out of IS5 from element-internal promoters was negligible, in the case of MG1655 a major transcript was found to extend into the insertion element. This suggests that IS5-specific transcription can be influenced by the specific location of the element in the chromosome, the orientation it adopts and the gene it interrupts.
移动插入元件IS5是一段相对较小但基因结构紧凑的1195bp DNA序列，在大肠杆菌菌株基因组中的拷贝数可变。本研究对大肠杆菌菌株MC4100和MG1655中存在的IS5元件群体进行了详细的转录分析。研究结果表明，由978bp组成的ins5A基因从其自身启动子转录，该启动子位于元件的右端附近。两个反向转录的基因ins5C和in5B形成一个操纵子，并且该转录本完全包含在ins5A转录本的边界内。尽管从元件内部启动子进行的IS5转录可以忽略不计，但在MG1655的情况下，发现一个主要转录本延伸到插入元件中。这表明IS5特异性转录可能受该元件在染色体中的特定位置、其采用的方向以及它中断的基因的影响。
