A MISMATCH RECOGNITION DEFECT IN COLON-CARCINOMA CONFERS DNA MICROSATELLITE INSTABILITY AND A MUTATOR PHENOTYPE
A MISMATCH RECOGNITION DEFECT IN COLON-CARCINOMA CONFERS DNA MICROSATELLITE INSTABILITY AND A MUTATOR PHENOTYPE
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DOI：
10.1073/pnas.91.19.8905
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发表时间：
1994-09-13
影响因子：
11.1
通讯作者：
BIGNAMI, M
中科院分区：
文献类型：
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作者：
AQUILINA, G;HESS, P;BIGNAMI, M
我们分析了中国仓鼠克隆B细胞中腺嘌呤磷酸核糖转移酶基因的自发突变，这些细胞由于错配结合缺陷而表现出突变表型。增变基因表型增加了有限数量的突变类型。转换率和大多数颠换没有显着增加。A到T的颠换率和-2的移码率显著升高。这些突变在重复元件中，9个移码中有5个是类似于微卫星的DNA序列中的二核苷酸缺失。在突变体系中有缺陷的错配结合蛋白是G.T错配识别因子。带移分析表明，错配识别蛋白的优选底物是重复序列内含有螺旋外单或二核苷酸的双链DNA。与防止负移码的作用一致，缺陷结合蛋白赋予克隆B微卫星DNA的不稳定性。在人结肠直肠癌细胞系LoVo中也检测到错配结合缺陷。克隆B或第二个错配结合缺陷系Raji-F12的提取物不与LoVo提取物互补，表明这些系具有共同的缺陷。我们的数据提供了一个机制解释之间的关系有缺陷的错配识别和人类结肠癌的微卫星不稳定性。
We have analyzed spontaneous mutations in the adenine phosphoribosyltransferase gene of Chinese hamster clone B cells that exhibit a mutator phenotype because of defective mismatch binding. The mutator phenotype conferred increases in a limited number of mutational classes. The rates of transitions and most transversions were not significantly increased. The rates of A to T transversions and -2 frameshifts were strikingly elevated. These mutations were in repeated elements and 5 of 9 of the frameshifts were dinucleotide deletions in DNA Sequences resembling microsatellites. The mismatch binding protein that is defective in the mutator line is a G.T mismatch recognition factor. Band-shift analysis indicated that the preferred substrate for the mismatch recognition protein is duplex DNA containing an extrahelical mono- or dinucleotide within repeated sequences. In agreement with a role in preventing minus frameshifts, a defective binding protein conferred an instability in clone B microsatellite DNA. A mismatch binding defect was also detected in LoVo, a human colorectal carcinoma cell line. Extracts of clone B or a second mismatch binding-deficient line, Raji-F12, did not complement LoVo extracts, indicating that these lines share a common defect. Our data provide a mechanistic explanation for the relation between defective mismatch recognition and the microsatellite instability of human colon cancer.