Loss of DNA ligase IV prevents recognition of DNA by double-strand break repair proteins XRCC4 and XLF
Loss of DNA ligase IV prevents recognition of DNA by double-strand break repair proteins XRCC4 and XLF
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DOI：
10.1093/nar/gkn552
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发表时间：
2008-10-01
影响因子：
14.9
通讯作者：
Hanakahi, Les A.
中科院分区：
文献类型：
--
作者：
Jayaram, Sumithra;Ketner, Gary;Hanakahi, Les A.
通过非同源末端连接（NHEJ）修复DNA双链断裂对于维持基因组完整性和细胞活力是必不可少的。NHEJ分子机制的核心是DNA连接酶IV/XRCC 4/XLF复合物，其重新连接DNA。在腺病毒（Ad 5）感染期间，连接酶IV在需要表达病毒E1 B 55 k和E4 34 k蛋白的过程中被靶向降解，而XRCC 4和XLF蛋白水平保持不变。我们发现，在Ad 5感染的细胞中，连接酶IV的丢失伴随着XRCC 4的DNA结合丢失。E1 B 55 k和E4 34 k的表达足以引起连接酶IV的损失和XRCC 4 DNA结合的损失。使用连接酶IV突变体人细胞系，我们确定连接酶IV的不存在和病毒蛋白的不表达与XRCC 4对DNA结合的抑制相一致。在连接酶IV突变的人细胞系中，XLF的DNA结合也被抑制。野生型和腺苷酸化突变体连接酶IV在连接酶IV缺陷细胞中的表达恢复了XRCC 4的DNA结合。这些数据表明，XRCC 4和XLF的内在DNA结合活性可能受到调节，并且在缺乏连接酶IV的人细胞中下调。
The repair of DNA double-strand breaks by nonhomologous end-joining (NHEJ) is essential for maintenance of genomic integrity and cell viability. Central to the molecular mechanism of NHEJ is DNA ligase IV/XRCC4/XLF complex, which rejoins the DNA. During adenovirus (Ad5) infection, ligase IV is targeted for degradation in a process that requires expression of the viral E1B 55k and E4 34k proteins while XRCC4 and XLF protein levels remain unchanged. We show that in Ad5-infected cells, loss of ligase IV is accompanied by loss of DNA binding by XRCC4. Expression of E1B 55k and E4 34k was sufficient to cause loss of ligase IV and loss of XRCC4 DNA binding. Using ligase IV mutant human cell lines, we determined that the absence of ligase IV, and not expression of viral proteins, coincided with inhibition of DNA binding by XRCC4. In ligase IV mutant human cell lines, DNA binding by XLF was also inhibited. Expression of both wild-type and adenylation-mutant ligase IV in ligase IV-deficient cells restored DNA binding by XRCC4. These data suggest that the intrinsic DNA-binding activities of XRCC4 and XLF may be subject to regulation and are down regulated in human cells that lack ligase IV.