Peterson S R, Kurimasa A, Oshimura M, Dynan W S, Bradbury E M, Chen D J
Life Sciences Division, Los Alamos National Laboratory, NM 87545, USA.
Proc Natl Acad Sci U S A. 1995 Apr 11;92(8):3171-4. doi: 10.1073/pnas.92.8.3171.
The DNA-dependent protein kinase (DNA-PK) consists of three polypeptide components: Ku-70, Ku-80, and an approximately 350-kDa catalytic subunit (p350). The gene encoding the Ku-80 subunit is identical to the x-ray-sensitive group 5 complementing gene XRCC5. Expression of the Ku-80 cDNA rescues both DNA double-strand break (DSB) repair and V(D)J recombination in group 5 mutant cells. The involvement of Ku-80 in these processes suggests that the underlying defect in these mutant cells may be disruption of the DNA-PK holoenzyme. In this report we show that the p350 kinase subunit is deleted in cells derived from the severe combined immunodeficiency mouse and in the Chinese hamster ovary cell line V-3, both of which are defective in DSB repair and V(D)J recombination. A centromeric fragment of human chromosome 8 that complements the scid defect also restores p350 protein expression and rescues in vitro DNA-PK activity. These data suggest the scid gene may encode the p350 protein or regulate its expression and are consistent with a model whereby DNA-PK is a critical component of the DSB-repair pathway.
DNA依赖性蛋白激酶（DNA-PK）由三个多肽成分组成：Ku-70、Ku-80和一个约350 kDa的催化亚基（p350）。编码Ku-80亚基的基因与X射线敏感的第5互补组基因XRCC5相同。Ku-80 cDNA的表达可挽救第5组突变细胞中的DNA双链断裂（DSB）修复和V（D）J重组。Ku-80参与这些过程表明，这些突变细胞中的潜在缺陷可能是DNA-PK全酶的破坏。在本报告中，我们表明，严重联合免疫缺陷小鼠来源的细胞和中国仓鼠卵巢细胞系V-3中缺失了p350激酶亚基，这两种细胞在DSB修复和V（D）J重组方面均存在缺陷。一个与scid缺陷互补的人8号染色体着丝粒片段也可恢复p350蛋白表达并挽救体外DNA-PK活性。这些数据表明，scid基因可能编码p350蛋白或调节其表达，并且与DNA-PK是DSB修复途径的关键组成部分的模型一致。
