Nonselective DNA damage induced by a replication inhibitor results in the selective elimination of extrachromosomal double minutes from human cancer cells
Nonselective DNA damage induced by a replication inhibitor results in the selective elimination of extrachromosomal double minutes from human cancer cells
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DOI：
10.1002/gcc.20473
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发表时间：
2007-10-01
影响因子：
3.7
通讯作者：
Utani, Koh-ichi
中科院分区：
文献类型：
--
作者：
Shimizu, Noriaki;Misaka, Naomi;Utani, Koh-ichi
基因扩增在人类恶性肿瘤中起着关键作用。高度扩增的基因经常定位于染色体外双微体（dmin），它通常与有丝分裂染色体分离到子细胞。我们和其他人已经表明，用低剂量的羟基脲（HU）治疗导致dmin的消除和癌细胞表型的逆转。在早期S期（dmin复制时）进行HU处理，导致其在下一个M期从染色体上脱离，导致出现富含dmin的微核，然后消除。在这篇文章中，我们研究了低剂量HU对dmin行为的影响，与DNA损伤诱导有关，同时监测LacO标记的dmin和磷酸化组蛋白H2 AX（gamma H2 AX）。正如预期的那样，低剂量HU治疗在早期S期诱导了大量的γ H2 AX病灶，这些病灶很少与dmin一致。大多数染色体γ H2 AX病灶消失中期，而出乎意料的是，那些持续经常与dmin。我们发现，这些dmin聚集，脱离后期染色体，并显然形成微核。由于γ H2 AX灶可能代表DNA双链断裂（DSB），因此对染色体外dmin持续的DSB的反应似乎与染色体位点持续的反应不同，这可以解释为什么DSB诱导剂导致dmin的选择性消除。(c)2007 Wiley-Liss，Inc.
Gene amplification plays a pivotal role in human malignancy. Highly amplified genes frequently localize to extrachromosomal double minutes (dmin), which usually segregate to daughter cells in association with mitotic chromosomes. We and others had shown that treatment with low-dose hydroxyurea (HU) results in the elimination of dmin and reversion of the cancer cell phenotype. HU treatment in early S-phase, when dmin are replicated, results in their detachment from chromosomes at the next M-phase, leading to the appearance of micronuclei enriched in dmin, followed by their elimination. In this article, we examined the effect of low-dose HU on the behavior of dmin in relation to DNA damage induction by simultaneously monitoring LacO-tagged dmin and phosphorylated histone H2AX (gamma H2AX). As expected, treatment with low-dose HU induced numerous gamma H2AX foci throughout the nucleus in early S-phase, and these rarely coincided with dmin. Most chromosomal gamma H2AX foci disappeared by metaphase, whereas, unexpectedly, those that persisted frequently associated with dmin. We found that these dmin aggregated, detached from anaphase chromosomes, and apparently formed micronuclei. Because gamma H2AX foci likely represent DNA double strand breaks (DSBs), the response to DSBs sustained by extrachromosomal dmin appears to be different from that sustained by chromosomal loci, which may explain why DSB-inducing agents cause the selective elimination of dmin. (c) 2007 Wiley-Liss, Inc.