Sequence interruptions confer differential stability at microsatellite alleles in mismatch repair-deficient cells
Sequence interruptions confer differential stability at microsatellite alleles in mismatch repair-deficient cells
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DOI：
10.1093/hmg/9.18.2707
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发表时间：
2000-11-01
影响因子：
3.5
通讯作者：
Dunlop, MG
中科院分区：
文献类型：
--
作者：
Bacon, AL;Farrington, SM;Dunlop, MG
考虑到与理解人类种群中此类序列突变的进化有关，给定微卫星重复序列的不稳定性决定因素值得研究。微卫星D2S123是一个典型的CA重复标记，也是遗传性非息肉病性结直肠癌分子筛查的推荐标记之一。本研究表明，D2S123基因座的突变率明显受重复区段内等位基因序列变异的影响。我们采用了一种新的方法来表征D2S123不稳定的本质，通过利用来自非肿瘤谱系的细胞，其包含显性的负错配修复(MMR)突变和突变子表型，使用半定量小池PCR技术对个体等位基因进行分型，这表明了实质性的等位基因--这些对D2S123基因座突变易感性的特异性偏差，为了支持这些体外数据，在41名HNPCC患者的肿瘤中也观察到了等位基因突变率的偏差，这取决于构成的基因型，细胞系和患者DNA的测序显示，由于存在不间断的CA重复序列，短等位基因更容易发生突变。长D2S123等位基因本质上更稳定，因为TA散布在重复区段，除了扩大对CA重复二核苷酸区段突变的理解外，这些发现还与筛查程序和微卫星不稳定性(MSI)与结肠癌生存率的相关性有相当大的相关性。肿瘤MSI的表现可能主要受构成基因的影响。
Determinants of instability at a given microsatellite repeat merits investigation in view of relevance to understanding evolution of mutations at such sequences in human populations. The microsatellite D2S123 was studied as a paradigm CA repeat marker, Furthermore, this marker is one of a recommended panel used in molecular screening for hereditary non-polyposis colorectal cancer (HNPCC), In this investigation we show that the mutation rate at the D2S123 locus is markedly influenced by intra-allelic sequence variation within the repetitive tract itself. We employed a novel approach to characterize the nature of instability at D2S123, by utilizing cells derived from a non-tumour lineage, which harbour a dominant negative mismatch repair (MMR) mutation and a mutator phenotype, Individual alleles were typed using a semi-quantitative small pool PCR technique and this demonstrated substantial allele-these specific bias in susceptibility to mutation at the D2S123 locus, In support of these in vitro data, bias in allele mutation rate was also observed in tumours from 41 HNPCC patients, which was dependent on constitutional genotype, Sequencing of cell line and patient DNAs revealed that short alleles are significantly more susceptible to mutation due to the presence of uninterrupted CA repeats. Long D2S123 alleles are intrinsically more stable because of a TA interspersion within the repetitive tract, In addition to extending understanding of mutation at CA repeat dinucleotide tracts, these findings have considerable relevance both to screening programmes and to correlation of microsatellite instability (MSI) with colon cancer survival. The manifestation of tumour MSI may be substantially influenced by constitutional genotype.