Ji W, Zhang X Y, Warshamana G S, Qu G Z, Ehrlich M
Department of Biochemistry, Tulane Medical School, New Orleans, Louisiana 70112, USA.
PCR Methods Appl. 1994 Oct;4(2):109-16. doi: 10.1101/gr.4.2.109.
We have studied the effect of repeated DNA sequence, especially Alu repeats, on PCR. Alu repeats are sequences that are approximately 300 bp long and interspersed at a very high copy number throughout the human genome. We amplified part of the human low-density lipoprotein receptor gene containing two Alu repeat sequences in the same orientation, approximately 7.8 kb apart, with unique sequence primers outside these repeats. The major PCR product was a DNA fragment with an in vitro deletion between the Alu repeats. The formation of this product depended on the template concentration and the type of polymerase used. Such a product arose apparently as a result of a "jumping reaction" involving a primer whose extension was terminated prematurely within one Alu repeated followed by annealing of such an incompletely extended primer to the other, distant Alu repeat. No such jumping products were seen when a 0.8-kb region containing two nearby inverted Alu repeats within the human alpha-galactosidase A gene was subject to PCR with unique sequence primers annealing just outside these repeats.
我们研究了重复DNA序列，尤其是Alu重复序列对聚合酶链式反应（PCR）的影响。Alu重复序列是长度约为300碱基对（bp）的序列，以非常高的拷贝数散布于整个人类基因组中。我们用位于这些重复序列之外的特异性序列引物，扩增了人类低密度脂蛋白受体基因的一部分，该部分包含两个同向的Alu重复序列，相距约7.8千碱基对（kb）。主要的PCR产物是一个在Alu重复序列之间存在体外缺失的DNA片段。该产物的形成取决于模板浓度和所用聚合酶的类型。这种产物显然是由于一种“跳跃反应”产生的，该反应涉及一个引物，其延伸在一个Alu重复序列内过早终止，随后这种未完全延伸的引物与另一个较远的Alu重复序列退火。当对人类α - 半乳糖苷酶A基因内包含两个相邻反向Alu重复序列的0.8 kb区域，用位于这些重复序列之外退火的特异性序列引物进行PCR时，未观察到这种跳跃产物。
