Fomukong N, Beggs M, el Hajj H, Templeton G, Eisenach K, Cave M D
Department of Anatomy, University of Arkansas for Medical Sciences, Little Rock, USA.
Tuber Lung Dis. 1997;78(2):109-16. doi: 10.1016/s0962-8479(98)80003-8.
Mycobacterium tuberculosis (M. tuberculosis) isolates from various parts of the USA which have few copies of the insertion sequence IS6110.
To characterize the sites of insertion of IS6110 among M. tuberculosis isolates that have one to six copies of the insertion sequence.
The mixed-linker polymerase chain reaction (ML-PCR) procedure was used to amplify the terminal repeats on the ends of IS6110 and adjacent flanking sequences. From the ML-PCR products, sequences flanking 14 copies of IS6110 in strains containing less than seven copies of the insertion were determined. Sequence information from the flanking deoxyribonucleic acid was used to construct flanking primers that can be used to indicate the presence of IS6110 at a particular site when paired with outbound IS6110 primers in a PCR. Over 200 strains of diverse origin were screened for the insertion of IS6110 at several distinct sites using this procedure.
The direct repeat (DR) locus has been described as a highly preferred site for insertion of IS6110 in strains of M. tuberculosis. Another highly preferred site of insertion of IS6100, DK1, is herein described. Insertions at DK1 are highly prevalent in M. tuberculosis strains harboring two to six copies of IS6110. The prevalence of insertions at this site decreases in strains with more than six copies of IS6110, even though the sequence itself is present in strains lacking a copy of IS6110 at this site.
In addition to the DR locus there are other conserved sites of insertion among M. tuberculosis strains. The data further suggest a separate lineage for the high copy and the low copy strains, and a possible sequential insertion of IS6110 in strains of M. tuberculosis with less than seven copies.
从美国各地分离出的结核分枝杆菌（M. tuberculosis）菌株，其插入序列IS6110的拷贝数较少。
对插入序列拷贝数为1至6个的结核分枝杆菌菌株中IS6110的插入位点进行特征分析。
采用混合接头聚合酶链反应（ML-PCR）方法扩增IS6110两端的末端重复序列及相邻侧翼序列。从ML-PCR产物中，确定了插入序列拷贝数少于7个的菌株中14个IS6110拷贝的侧翼序列。利用侧翼脱氧核糖核酸的序列信息构建侧翼引物，当与PCR中的外向IS6110引物配对时，可用于指示特定位点是否存在IS6110。使用该方法对200多种不同来源的菌株进行筛选，以确定IS6110在几个不同位点的插入情况。
直接重复序列（DR）位点已被描述为结核分枝杆菌菌株中IS6110插入的高度优先位点。本文描述了另一个IS6110插入的高度优先位点DK1。在含有2至6个IS6110拷贝的结核分枝杆菌菌株中，DK1位点的插入非常普遍。在IS6110拷贝数超过6个的菌株中，该位点的插入发生率降低，尽管在该位点缺乏IS6110拷贝的菌株中也存在该序列本身。
除DR位点外，结核分枝杆菌菌株中还存在其他保守的插入位点。数据进一步表明高拷贝和低拷贝菌株属于不同的谱系，并且在拷贝数少于7个的结核分枝杆菌菌株中，IS6110可能存在顺序插入。
