Mutation rate at the hprt locus in human cancer cell lines with specific mismatch repair-gene defects
Mutation rate at the hprt locus in human cancer cell lines with specific mismatch repair-gene defects
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DOI：
10.1093/carcin/18.1.1
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发表时间：
1997-01-01
期刊：
影响因子：
4.7
通讯作者：
Tindall, KR
中科院分区：
文献类型：
--
作者：
Glaab, WE;Tindall, KR
在错配修复（NMR）基因hMLH1、hPMS2或GTBP缺陷的人癌细胞系中，以及在hMLH1和hPMS2均携带突变的细胞系中，测量次黄嘌呤-鸟嘌呤磷酸核糖转移酶（hprt）位点的自发突变率。通过定量单一培养物内突变频率增加作为细胞分裂的函数来确定突变率。这些MMR缺陷细胞系相对于MMR熟练癌细胞系表现出突变率增加50至750倍。从最低到最高，相对于此处研究的MMR基因缺陷的自发突变率如下：hMLH1（-）<GTBP（-）<hPMS2（-）<hMLH1（-）/hPMS2（-）。此外，通过染色体转移恢复MMR的细胞系的突变率比MMR缺陷的亲本细胞系低12倍。这些数据支持MMR在控制自发突变速率中起重要作用的观点，并表明不同的MMR基因缺陷在修复不同类型的DNA错配的能力方面可能不同，从而导致自发突变的可测量的定量差异。在hPMS2缺陷细胞系之间观察到突变率的差异，（3.1 x 10（-5）突变/细胞/代）和两个hMLH1缺陷细胞系（4.0 x 10（-6）和7.3 x 10（-6）突变/细胞/代）。假设hPMS2-和hMLH1-基因产物仅在提出的hMutL α异二聚体中起作用，则任一基因中的缺陷应产生相当的突变率。这些数据表明，hPMS2在MMR中起关键作用，而另外的hMLH1同源物或单独的hPMS2可能起部分补充hMLH1缺陷的作用。
Spontaneous mutation rates at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus were measured in human cancer cell lines defective in the mismatch repair (NMR) genes hMLH1, hPMS2, or GTBP, as well as in a cell line carrying mutations in both hMLH1 and hPMS2. The mutation rate was determined by quantitating mutant frequency increases within a single culture as a function of cell division, These MMR-deficient cell lines exhibited a 50- to 750-fold increase in mutation rate relative to a MMR-proficient cancer cell line, From lowest to highest, the spontaneous mutation rates relative to the MMR-gene defects studied here are as follows: hMLH1(-) < GTBP(-) < hPMS2(-) < hMLH1(-)/hPMS2(-). In addition, a cell line in which MMR was restored by chromosome transfer exhibited a mutation rate 12-fold below the MMR-deficient parental cell line. These data support the notion that MMR plays an important role in controlling the rate of spontaneous mutation and suggest that different MMR-gene defects may vary in their ability to repair different types of DNA mismatches, thus leading to measurable quantitative differences in spontaneous mutagenesis, Furthermore, a difference in mutation rates was observed between a hPMS2-defective cell line (3.1 x 10(-5) mutations/ cell/generation) and two hMLH1-defective cell lines (4.0 x 10(-6) and 7.3 x 10(-6) mutations/cell/generation). Assuming the hPMS2- and hMLH1-gene products only function in the proposed hMutL alpha heterodimer, then defects in either gene should yield comparable mutation rates, These data suggest that hPMS2 plays a critical role in MMR, while additional hMLH1 homologues or hPMS2 alone may function to partially complement defects in hMLH1.