MCPH1 patient cells exhibit delayed release from DNA damage-induced G2/M checkpoint arrest
MCPH1 patient cells exhibit delayed release from DNA damage-induced G2/M checkpoint arrest
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DOI：
10.4161/cc.9.24.14157
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发表时间：
2010-12-15
期刊：
影响因子：
4.3
通讯作者：
Trimborn, Marc
中科院分区：
文献类型：
--
作者：
Gavvovidis, Ioannis;Poehlmann, Charlotte;Trimborn, Marc
MCPH 1基因突变导致原发性小头畸形，并伴有染色体浓缩失调的独特细胞表型。编码的蛋白质包含三个BRCT结构域，并且积累的数据显示MCPH 1参与DNA损伤反应。然而，大多数证据是通过使用RNA干扰（RNAi）和来自非人类模式生物的细胞的实验产生的。在这里，我们证明了患者来源的细胞系显示一个熟练的G（2）/M检查点电离辐射（IR）后，尽管纯合截断突变MCPH 1。此外，在这些细胞中，染色体断裂率和几种蛋白质以MCPH 1依赖的方式作用于puppatients的DNA修复灶的重新定位是正常的。然而，MCPH 1缺陷的细胞表现出轻微的延迟，重新进入有丝分裂和延迟决议γ H2 AX焦点后IR。分析染色体浓缩行为后IR表明，这些后者的观察可能与超浓缩的染色质在细胞中与MCPH 1突变。我们的研究结果表明，截短MCPH 1突变的人类细胞中的DNA损伤反应显着不同的某些模式生物的细胞和细胞中的MCPH 1的RNAi耗尽的损伤反应。人类MCPH 1缺陷对细胞DNA损伤反应的这些微妙影响可能解释了双等位基因MCPH 1突变患者缺乏癌症易感性。
Mutations in the MCPH1 gene cause primary microcephaly associated with a unique cellular phenotype of misregulated chromosome condensation. The encoded protein contains three BRCT domains, and accumulating data show that MCPH1 is involved in the DNA damage response. However, most of this evidence has been generated by experiments using RNA interference (RNAi) and cells from non-human model organisms. Here, we demonstrate that patient-derived cell lines display a proficient G(2)/M checkpoint following ionizing irradiation (IR) despite homozygous truncating mutations in MCPH1. Moreover, chromosomal breakage rates and the relocation to DNA repair foci of several proteins functioning putatively in an MCPH1-dependent manner are normal in these cells. However, the MCPH1-deficient cells exhibit a slight delay in re-entering mitosis and delayed resolution of gamma H2AX foci following IR. Analysis of chromosome condensation behavior following IR suggests that these latter observations may be related to hypercondensation of the chromatin in cells with MCPH1 mutations. Our results indicate that the DNA damage response in human cells with truncating MCPH1 mutations differs significantly from the damage responses in cells of certain model organisms and in cells depleted of MCPH1 by RNAi. These subtle effects of human MCPH1 deficiency on the cellular DNA damage response may explain the absence of cancer predisposition in patients with biallelic MCPH1 mutations.