Ku80-deficient cells exhibit excess degradation of extrachromosomal DNA
Ku80-deficient cells exhibit excess degradation of extrachromosomal DNA
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DOI：
10.1074/jbc.271.24.14405
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发表时间：
1996-06-14
影响因子：
4.8
通讯作者：
Jasin, M
中科院分区：
文献类型：
--
作者：
Liang, F;Jasin, M
哺乳动物细胞具有一种蛋白质复合体，称为DNA-PII，它在体外与DNA双链断裂结合。该复合体由异二聚体Ru自身抗原和DNA依赖的蛋白激酶DNA-PKcs组成。缺乏这种复合体成分的细胞系对电离辐射敏感，并损害了V(D)J重组，这是一种特定部位的重组过程。我们测试了这些细胞系修复转基因DNA双链断裂的能力。缺乏Ru自身抗原80 kDa亚单位的XRS-6细胞株表现出转基因DNA的稳定性降低。在DNA稳定性明显下降之前，同源重组和DNA末端连接的水平没有受到影响。然而，具有精确连接末端的末端连接产品的回收率降低，伴随而来的是含有缺失的产品的增加。与Ku80缺陷的细胞不同，DNA-PKcs缺陷的SCID细胞没有检测到DNA稳定性的降低。SCID细胞也表现出正常水平的同源重组和DNA末端连接。这些实验表明，Ru自身抗原，而不是DNA-PKcs，在保护DNA末端免受降解方面起到了直接作用。
Mammalian cells possess a protein complex, termed DNA-PII, which binds to DNA double strand breaks in vitro. The complex consists of the heterodimeric Ru autoantigen and a DNA-dependent protein kinase, DNA-PKcs. Cell lines that are deficient for components of this complex are sensitive to ionizing radiation and have impaired V(D)J recombination, a site-specific recombination process. We have tested these cell lines for their ability to repair double strand breaks in transfected DNA. The xrs-6 cell line, which is deficient for the 80-kDa subunit of the Ru autoantigen, exhibited reduced stability of transfected DNA. Prior to obvious reductions in DNA stability, the levels of homologous recombination and DNA end joining were unaffected. However, the recovery of end joining products with precisely joined ends was reduced, with a concomitant increase in products containing deletions. Unlike the Ku80-deficient cells, no reduction in DNA stability was detected in DNA-PKcs-deficient scid cells. Scid cells also exhibited normal levels of homologous recombination and DNA end joining. These experiments implicate the Ru autoantigen, but not DNA-PKcs, in a direct role in protecting DNA ends from degradation.