A single mutated BRCA1 allele leads to impaired fidelity of double strand break end-joining
A single mutated BRCA1 allele leads to impaired fidelity of double strand break end-joining
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DOI：
10.1038/sj.onc.1205200
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发表时间：
2002-02-21
期刊：
影响因子：
8
通讯作者：
Papadopoulo, D
中科院分区：
文献类型：
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作者：
Baldeyron, C;Jacquemin, E;Papadopoulo, D
人类BRCA 1基因突变的杂合性赋予了患乳腺癌的高风险，但这种表型的生化基础尚未确定。越来越多的证据表明BRCA 1在维持基因组完整性和保护细胞免受DNA双链断裂（DSB）方面起作用。在这里，我们提出的证据表明，BRCA 1突变杂合子的人类细胞表现出受损的DNA末端连接，这是在哺乳动物体细胞的主要DSB修复途径。使用体内宿主细胞末端连接测定，我们观察到与两个对照细胞系相比，三个BRCA 1（+/-）细胞系中DNA末端连接的保真度强烈降低。此外，无细胞BRCA 1（+/-）提取物不能促进体外反应中准确的DNA末端连接。野生型BRCA 1蛋白的稳态水平显著低于BRCA 1（+/-）细胞中预期的50%，因此可能是观察到的末端连接缺陷的基础。总之，这些数据有力地表明，BRCA 1对于断裂DNA末端的忠实重新连接是必要的，并且单个突变的BRCA 1等位基因足以削弱这一过程。这种缺陷将损害BRCA 1生殖系突变携带者的基因组稳定性，引发肿瘤转化启动所需的遗传变化。
Heterozygosity for mutations in the BRCA1 gene in humans confers high risk for developing breast cancer, but a biochemical basis for this phenotype has not yet been determined. Evidence has accumulated implicating BRCA1, in the maintenance of genomic integrity and the protection of cells against DNA double strand breaks (DSB). Here we present evidence that human cells heterozygous for BRCA1 mutations exhibit impaired DNA end-joining, which is the major DSB repair pathway in mammalian somatic cells. Using an in vivo host cell end-joining assay, we observed that the fidelity of DNA end-joining is strongly reduced in three BRCA1(+/-) cell lines in comparison to two control cell lines. Moreover, cell-free BRCA1(+/-) extracts are unable to promote accurate DNA end-joining in an in vitro reaction. The steady-state level of the wild type BRCA1 protein was significantly lower than the 50% expected in BRCA1(+/-) cells and thus may underlie the observed end-joining defect. Together, these data strongly suggest that BRCA1 is necessary for faithful rejoining of broken DNA ends and that a single mutated BRCA1 allele is sufficient to impair this process. This defect will compromise genomic stability in BRCA1 germ-line mutation carriers, triggering the genetic changes necessary for the initiation of neoplastic transformation.