Hermans P W, van Soolingen D, Bik E M, de Haas P E, Dale J W, van Embden J D
National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands.
Infect Immun. 1991 Aug;59(8):2695-705. doi: 10.1128/iai.59.8.2695-2705.1991.
Most strains of the Mycobacterium tuberculosis complex carry multiple copies of an IS3-like element, and these strains are highly polymorphic with regard to the site of integration in the chromosome. In contrast, Mycobacterium bovis BCG contains a single copy of the insertion element, and in all strains this copy is integrated at the same site in the chromosome. In this study, we determined the sequence of the single-copy insertion element from M. bovis BCG, IS987, and its flanking regions. The analysis of IS987 revealed that this element was virtually identical to the sequence of IS986 from M. tuberculosis. IS987 is located in a region containing direct repeats (DRs). The cloned flanking regions contained 20 virtually identical DRs of 36 bp, each separated by 35 to 41 bp of spacer DNA. Analysis of chromosomal DNA by the polymerase chain reaction revealed the presence of a cluster of 49 DRs, and IS987 is inserted in the 30th DR. Furthermore, the DR sequences were found to occur only in species of the M. tuberculosis complex and not in nine other mycobacterial species tested. Analysis of 14 M. tuberculosis strains revealed the presence of one insertion sequence element in the DR-containing region of eight strains, two insertion sequence elements were located in the DR region of five strains, and one strain did not contain an insertion sequence element in this region. Additionally, the DR-containing regions of these 14 M. tuberculosis strains were polymorphic in length and composition. We conclude that the DR cluster is a specific, hot-spot region for integration of insertion elements in the chromosome of M. tuberculosis complex strains.
结核分枝杆菌复合群的大多数菌株携带多个IS3样元件拷贝，并且这些菌株在染色体上的整合位点高度多态。相比之下，牛分枝杆菌卡介苗（Mycobacterium bovis BCG）含有单个插入元件拷贝，并且在所有菌株中该拷贝都整合在染色体的同一位置。在本研究中，我们确定了来自牛分枝杆菌卡介苗的单拷贝插入元件IS987及其侧翼区域的序列。对IS987的分析表明，该元件实际上与结核分枝杆菌的IS986序列相同。IS987位于一个含有同向重复序列（DRs）的区域。克隆的侧翼区域包含20个几乎相同的36 bp同向重复序列，每个同向重复序列被35至41 bp的间隔DNA隔开。通过聚合酶链反应对染色体DNA的分析揭示了存在一个由49个同向重复序列组成的簇，并且IS987插入到第30个同向重复序列中。此外，发现同向重复序列仅存在于结核分枝杆菌复合群的物种中，而在所测试的其他9种分枝杆菌物种中不存在。对14株结核分枝杆菌菌株的分析表明，8株菌株的含同向重复序列区域存在一个插入序列元件，5株菌株的同向重复序列区域有两个插入序列元件，1株菌株在该区域不含有插入序列元件。此外，这14株结核分枝杆菌菌株的含同向重复序列区域在长度和组成上具有多态性。我们得出结论，同向重复序列簇是结核分枝杆菌复合群菌株染色体中插入元件整合的一个特定热点区域。
