Homology-directed dna repair, mitomycin-c resistance, and chromosome stability is restored with correction of a Brca1 mutation.
Homology-directed dna repair, mitomycin-c resistance, and chromosome stability is restored with correction of a Brca1 mutation.
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发表时间：
2001-06
期刊：
影响因子：
11.2
通讯作者：
M. Moynahan;Tracy Y. Cui;M. Jasin
中科院分区：
文献类型：
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作者：
M. Moynahan;Tracy Y. Cui;M. Jasin
由于正常的 DNA 代谢以及暴露于 DNA 损伤剂后，染色体断裂会自发发生。参与染色体双链断裂修复的主要途径是同源重组。在此途径中，与受损染色体相似的 DNA 序列指导损伤的修复。遗传性乳腺癌易感基因 BRCA1 和 BRCA2 的蛋白质产物与同源修复途径的核心成分 Rad51 蛋白质相互作用。我们最近通过证明 Brca1 和 BRCA2 缺陷细胞在同源定向染色体断裂修复方面存在缺陷，证明了这种相互作用的重要性。我们证实，Brca1 缺陷的胚胎干 (ES) 细胞在 I-Sce I 诱导的染色体断裂的基因靶向和同源定向修复方面存在缺陷。通过证明对链间交联剂丝裂霉素-C 的 100 倍敏感性和自发染色体不稳定性，定义同源定向修复突变体的表型范式已扩展到这些 Brca1 缺陷细胞。有趣的是，尽管染色体畸变很明显，但没有观察到非整倍性。 Brca1 转基因的表达可部分恢复修复表型，而通过基因靶向纠正一个突变的 Brca1 等位基因可完全恢复丝裂霉素-C 抗性和染色体稳定性。我们的结论是，无法通过同源定向修复正确修复链断裂会导致染色体维护缺陷，从而促进遗传不稳定，并可能促进肿瘤发生。
Chromosomal breaks occur spontaneously as a result of normal DNA metabolism and after exposure to DNA-damaging agents. A major pathway involved in chromosomal double-strand break repair is homologous recombination. In this pathway, a DNA sequence with similarity to a damaged chromosome directs the repair of the damage. The protein products of the hereditary breast cancer susceptibility genes, BRCA1 and BRCA2, interact with the Rad51 protein, a central component of homologous repair pathways. We have recently shown that this interaction is significant by demonstrating that Brca1- and BRCA2-deficient cells are defective in homology-directed chromosomal break repair. We confirm that Brca1-deficient embryonic stem (ES) cells are defective in gene targeting and homology-directed repair of an I-Sce I-induced chromosome break. The phenotypic paradigm that defines homology-directed repair mutants is extended to these Brca1-deficient cells by the demonstration of 100-fold sensitivity to the interstrand cross-linking agent mitomycin-C and spontaneous chromosome instability. Interestingly, although chromosome aberrations were evident, aneuploidy was not observed. Repair phenotypes are partially restored by expression of a Brca1 transgene, whereas correction of one mutated Brca1 allele through gene targeting fully restores mitomycin-C resistance and chromosome stability. We conclude that the inability to properly repair strand breaks by homology-directed repair gives rise to defects in chromosome maintenance that promote genetic instability and, it is likely, tumorigenesis.