Analysis of variable (diversity) joining recombination in DNA-dependent protein kinase (DNA-PK)-deficient mice reveals DNA-PK-independent pathways for both signal and coding joint formation
Analysis of variable (diversity) joining recombination in DNA-dependent protein kinase (DNA-PK)-deficient mice reveals DNA-PK-independent pathways for both signal and coding joint formation
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DOI：
10.1073/pnas.95.26.15559
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发表时间：
1998-12-22
影响因子：
11.1
通讯作者：
Roth, DB
中科院分区：
文献类型：
--
作者：
Bogue, MA;Jhappan, C;Roth, DB
先前的研究表明，电离辐射会导致小鼠和DNA依赖性蛋白激酶（DNA-PK）三个亚基中任何一个突变的细胞系发生不可修复的DNA双链断裂（催化亚基DNA-PKcs，或DNA结合亚基之一Ku 70或Ku 86），实际上，这些突变体在它们分辨可变的DNA序列中产生的双链断裂的能力上是不同的。在Ku 70或Ku 86中具有靶向缺失的突变细胞系和小鼠在其形成编码和信号接头（V（D）J重组的产物）的能力方面严重受损，然而，值得注意的是，严重的联合免疫缺陷（SCID）小鼠，其中携带的DNA-PKcs的非无效突变，在形成信号关节比编码关节的损害大大减少，目前的观点认为，由小鼠SCID等位基因编码的缺陷蛋白质保留足够的残余功能，以支持信号关节的形成。另一种假说提出DNA-PKcs和Ku在V（D）J重组中发挥不同的作用，DNA-PKcs仅用于编码联合形成。为了解决这个问题，我们研究了DNA-PKcs缺陷（SLIP）小鼠中的V（D）J重组。我们发现这种突变对编码和信号联合形成的影响与SCID突变的影响相同。信号关节形成的水平比野生型低10倍，这些关节中有一半是异常的。这些数据是不相容的概念，信号关节形成在SCID小鼠的结果从残留的DNA-PKcs功能，并提出了第三种可能性：DNA-PKcs通常起着重要的，但非必要的作用，在信号关节的形成。
Previous studies have suggested that ionizing radiation causes irreparable DNA double-strand breaks in mice and cell lines harboring mutations in any of the three subunits of DNA-dependent protein kinase (DNA-PK) (the catalytic subunit, DNA-PKcs, or one of the DNA-binding subunits, Ku70 or Ku86), In actuality, these mutants vary in their ability to resolve double-strand breaks generated during variable (diversity) joining [V(D)J] recombination, Mutant cell lines and mice with targeted deletions in Ku70 or Ku86 are severely compromised in their ability to form coding and signal joints, the products of V(D)J recombination, It is noteworthy, however, that severe combined immunodeficient (SCID) mice, which bear a nonnull mutation in DNA-PKcs, are substantially less impaired in forming signal joints than coding joints, The current view holds that the defective protein encoded by the murine SCID allele retains enough residual function to support signal joint formation. An alternative hypothesis proposes that DNA-PKcs and Ku perform different roles in V(D)J recombination, with DNA-PKcs required only for coding joint formation. To resolve this issue, we examined V(D)J recombination in DNA-PKcs-deficient (SLIP) mice. We found that the effects of this mutation on coding and signal joint formation are identical to the effects of the SCID mutation. Signal-joints are formed at levels 10-fold lower than in wild type, and one-half of these joints are aberrant. These data are incompatible with the notion that signal joint formation in SCID mice results from residual DNA-PKcs function, and suggest a third possibility: that DNA-PKcs normally plays an important but nonessential role in signal joint formation.