Unique pattern of ORC2 and MCM7 localization during DNA replication licensing in the mouse zygote.
Unique pattern of ORC2 and MCM7 localization during DNA replication licensing in the mouse zygote.
复制标题
小鼠受精卵 DNA 复制许可过程中 ORC2 和 MCM7 定位的独特模式。
DOI：
10.1095/biolreprod.112.101774
复制
发表时间：
2012
影响因子：
3.6
通讯作者：
Ward,WSteven
中科院分区：
文献类型：
--
作者：
Ortega,MichaelA;Marh,Joel;Alarcon,VernadethB;Ward,WSteven
在真核生物中，DNA合成之前是复制起点的许可。我们研究了两个许可蛋白，ORC2和MCM7，在小鼠受精卵和两细胞胚胎的亚细胞定位。在体细胞中，ORC2在整个细胞周期中保持与DNA复制起点结合，而MCM7是最后与许可复合物结合的蛋白质之一。我们发现，MCM7，而不是ORC 2结合到DNA在中期II卵母细胞，并保持与DNA，直到S期。受精后不久，ORC2在中期II纺锤体两极，然后在分离的染色体之间可检测到。这两种蛋白质都不存在于受精时的精子细胞中。随着精子头部的去致密化，MCM7与DNA结合，但未观察到ORC2。受精后4小时，两个原核含有DNA结合ORC2和MCM7。正如预期的那样，在第一个合子细胞周期的S期，MCM7从DNA中释放出来，但ORC2仍然结合。在合子有丝分裂期间，ORC 2再次首先定位于纺锤体极，然后定位于分离染色体之间的区域。然后，ORC 2在进入细胞核之前在发育中的两个细胞核周围形成一个环。只有可溶性的MCM7存在于G2原核中，但合子中期，它被绑定到DNA，再次显然在ORC 2之前。在两细胞期的G1期，两个细胞核都具有耐盐的ORC2和MCM7。这些数据表明，许可证遵循一个独特的模式，在早期受精卵，不同于已被描述为其他哺乳动物细胞已被研究。
In eukaryotes, DNA synthesis is preceded by licensing of replication origins. We examined the subcellular localization of two licensing proteins, ORC2 and MCM7, in the mouse zygotes and two-cell embryos. In somatic cells ORC2 remains bound to DNA replication origins throughout the cell cycle, while MCM7 is one of the last proteins to bind to the licensing complex. We found that MCM7 but not ORC2 was bound to DNA in metaphase II oocytes and remained associated with the DNA until S-phase. Shortly after fertilization, ORC2 was detectable at the metaphase II spindle poles and then between the separating chromosomes. Neither protein was present in the sperm cell at fertilization. As the sperm head decondensed, MCM7 was bound to DNA, but no ORC2 was seen. By 4 h after fertilization, both pronuclei contained DNA bound ORC2 and MCM7. As expected, during S-phase of the first zygotic cell cycle, MCM7 was released from the DNA, but ORC2 remained bound. During zygotic mitosis, ORC2 again localized first to the spindle poles, then to the area between the separating chromosomes. ORC2 then formed a ring around the developing two-cell nuclei before entering the nucleus. Only soluble MCM7 was present in the G2 pronuclei, but by zygotic metaphase it was bound to DNA, again apparently before ORC2. In G1 of the two-cell stage, both nuclei had salt-resistant ORC2 and MCM7. These data suggest that licensing follows a unique pattern in the early zygote that differs from what has been described for other mammalian cells that have been studied.