Human postmeiotic segregation 2 exhibits biased repair at tetranucleotide microsatellite sequences.
Human postmeiotic segregation 2 exhibits biased repair at tetranucleotide microsatellite sequences.
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DOI：
10.1158/0008-5472.can-08-3499
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发表时间：
2009-02-01
期刊：
影响因子：
11.2
通讯作者：
Eckert KA
中科院分区：
文献类型：
--
作者：
Shah SN;Eckert KA
错配修复（MMR）系统在消除DNA聚合错误中起着重要作用，该途径的缺失导致以微卫星不稳定性为特征的遗传性癌症。我们研究了在人类减数分裂后分离2（hPMS 2）缺陷和熟练的人类淋巴母细胞系的DNA复制过程中微卫星的稳定性。使用穿梭载体测定，我们测量了突变率在报告盒含有定义的单核苷酸，二核苷酸，和四核苷酸微卫星序列。在hPMS 2缺陷细胞系中观察到突变体表型。含有[G/C]10或[GT/CA]10等位基因的载体的突变率在hPMS 2缺陷细胞中相对于hPMS 2表达细胞系升高20倍至40倍。我们观察到在hPMS 2缺陷细胞中，[TTTC/AAAG]9和[TTCC/AAGG]9序列的突变率分别相对增加6倍和12倍。突变特异性分析表明，hPMS 2的修复是有偏见的。在不存在hPMS 2的情况下，观察到更多数量的微卫星扩展与缺失突变，并且四核苷酸等位基因的扩展率相似。在hPMS 2的存在下，我们观察到[TTCC/AAGG]9扩增速率降低29倍，但[TTTC/AAAG]9等位基因仅降低6倍。我们的数据表明，hPMS 2是更保护四核苷酸扩增比缺失和hPMS 2显示序列的偏见，其中[TTCC/AAGG]序列稳定到更大的程度比[TTTC/AAAG]。我们的研究结果允许更高的准确性，在识别MMR缺陷，通过提供一个突变的签名特征的hPMS 2缺陷。这项研究还提供了线索，可能的机制修复hPMS 2的背景下，MMR系统。
The mismatch repair (MMR) system plays a major role in removing DNA polymerization errors, and loss of this pathway results in hereditary cancers characterized by microsatellite instability. We investigated microsatellite stability during DNA replication within human postmeiotic segregation 2 (hPMS2)–deficient and proficient human lymphoblastoid cell lines. Using a shuttle vector assay, we measured mutation rates at reporter cassettes containing defined mononucleotide, dinucleotide, and tetranucleotide microsatellite sequences. A mutator phenotype was observed in the hPMS2-deficient cell line. The mutation rate of vectors containing [G/C]10 or [GT/CA]10 alleles was elevated 20-fold to 40-fold in hPMS2-deficient cells, relative to an hPMS2-expressing cell line. We observed a 6-fold and 12-fold relative increase in mutation rate of [TTTC/AAAG]9 and [TTCC/AAGG]9 sequences, respectively, in hPMS2-deficient cells. Mutational specificity analyses suggested that repair by hPMS2 is biased. In the absence of hPMS2, a greater number of microsatellite expansion versus deletion mutations was observed, and expansion rates of the tetranucleotide alleles were similar. In the presence of hPMS2, we observed a 29-fold decrease in the [TTCC/AAGG]9 expansion rate but only a 6-fold decrease for the [TTTC/AAAG]9 allele. Our data indicate that hPMS2 is more protective of tetranucleotide expansions than deletions and that hPMS2 displays a sequence bias, wherein [TTCC/AAGG] sequences are stabilized to a greater extent than [TTTC/AAAG]. Our results allow for greater accuracy during identification of MMR defects by providing a mutational signature characteristic of hPMS2 defect. This study also provides clues to possible mechanisms of repair by hPMS2 in the context of the MMR system.