Role of JC virus agnoprotein in DNA repair
Role of JC virus agnoprotein in DNA repair
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DOI：
10.1128/jvi.78.16.8593-8600.2004
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发表时间：
2004-08-01
影响因子：
5.4
通讯作者：
Khalili, K
中科院分区：
文献类型：
--
作者：
Darbinyan, A;Siddiqui, KM;Khalili, K
人类嗜神经JC病毒的晚期区域编码一种由71个氨基酸组成的小未知蛋白，该蛋白也存在于多瘤病毒猿猴病毒40和BK病毒中。已经鉴定了未知蛋白的几种功能，包括在调节病毒转录和病毒粒子成熟中的作用。早期的研究表明，单独表达的未知蛋白诱导p21/WAF-1的表达，并导致细胞在细胞周期的G（2）/M期积累。在这里，我们报告说，agnoprotein表达敏感细胞的DNA损伤剂顺铂的细胞毒性作用。Agnoprotein降低顺铂处理的细胞的活力，增加染色体断裂和微核形成。而顺铂处理的对照细胞积累在S期，细胞表达的agnoprotein没有，而是成为非整倍体。Agnoprotein表达与受损的双链断裂修复活性在细胞提取物和Ku 70和Ku 80 DNA修复蛋白的表达减少。在表达未知蛋白后，Ku 70蛋白主要定位于核周间隙，在核周间隙中也发现了未知蛋白，结合研究表明未知蛋白与Ku 70的相互作用是通过N端介导的。当它被添加到细胞提取物中时，未知蛋白抑制双链断裂修复活性的能力也由N末端介导。我们的结论是，agnoprotein抑制DNA损伤后的DNA修复和干扰DNA损伤诱导的细胞周期调控。由于Ku 70是DNA依赖性蛋白激酶的一个亚基，负责双链断裂修复和信号损伤诱导的细胞周期停滞，因此未知蛋白对Ku 70和/或Ku 80的调节可能代表多瘤病毒生命周期和细胞转化中的重要事件。
The late region of human neurotropic JC virus encodes a small 71-amino-acid agnoprotein that is also found in the polyomaviruses simian virus 40 and BK virus. Several functions of agnoprotein have been identified, including roles in regulating viral transcription and virion maturation. Earlier studies showed that agnoprotein expressed alone induced p21/WAF-1 expression and caused cells to accumulate in the G(2)/M stage of the cell cycle. Here we report that agnoprotein expression sensitized cells to the cytotoxic effects of the DNA-damaging agent cisplatin. Agnoprotein reduced the viability of cisplatin-treated cells and increased chromosome fragmentation and micronucleus formation. Whereas cisplatin-treated control cells accumulated in S phase, cells expressing agnoprotein did not, instead becoming aneuploid. Agnoprotein expression correlated with impaired double-strand-break repair activity in cellular extracts and reduced expression of the Ku70 and Ku80 DNA repair proteins. After agnoprotein expression, much of the Ku70 protein was located in the perinuclear space, where agnoprotein was also found. Results from binding studies showed an interaction of agnoprotein with Ku70 which was mediated by the N terminus. The ability of agnoprotein to inhibit double-strand break repair activity when it was added to cellular extracts was also mediated by the N terminus. We conclude that agnoprotein inhibits DNA repair after DNA damage and interferes with DNA damage-induced cell cycle regulation. Since Ku70 is a subunit of the DNA-dependent protein kinase that is responsible both for double-strand break repair and for signaling damage-induced cell cycle arrest, the modulation of Ku70 and/or Ku80 by agnoprotein may represent an important event in the polyomavirus life cycle and in cell transformation.