Cotter Laura, Allen Terence D, Kiseleva Elena, Goldberg Martin W
Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Wilmslow Road, Manchester M20 4BX, UK.
J Mol Biol. 2007 Jun 8;369(3):683-95. doi: 10.1016/j.jmb.2007.03.051. Epub 2007 Mar 24.
The nuclear envelope consists of two membranes traversed by nuclear pore complexes. The outer membrane is continuous with the endoplasmic reticulum. At mitosis nuclear pore complexes are dismantled and membranes disperse. The mechanism of dispersal is controversial: one view is that membranes feed into the endoplasmic reticulum, another is that they vesiculate. Using Xenopus egg extracts, nuclei have been assembled and then induced to breakdown by addition of metaphase extract. Field emission scanning electron microscopy was used to study disassembly. Strikingly, endoplasmic reticulum-like membrane tubules form from the nuclear surface after the addition of metaphase extracts, but vesicles were also observed. Microtubule inhibitors slowed but did not prevent membrane removal, whereas Brefeldin A, which inhibits vesicle formation, stops membrane disassembly, suggesting that vesiculation is necessary. Structures that looked like coated buds were observed and buds were labelled for beta-COP. We show that nuclear pore complexes are dismantled and the pore closed prior to membrane rupturing, suggesting that rupturing is an active process rather than a result of enlargement of nuclear pores.
核膜由两层被核孔复合体贯穿的膜组成。外膜与内质网相连。在有丝分裂时，核孔复合体被拆解，膜分散开来。膜分散的机制存在争议：一种观点认为膜融入内质网，另一种观点认为它们形成囊泡。利用非洲爪蟾卵提取物组装细胞核，然后通过添加中期提取物诱导其解体。使用场发射扫描电子显微镜研究解体过程。令人惊讶的是，添加中期提取物后，内质网样的膜小管从核表面形成，但也观察到了囊泡。微管抑制剂减缓了膜的去除，但并未阻止，而抑制囊泡形成的布雷菲德菌素A则阻止了膜的解体，这表明形成囊泡是必要的。观察到了类似包被小芽的结构，并对小芽进行了β-COP标记。我们表明，在膜破裂之前，核孔复合体被拆解且孔被关闭，这表明破裂是一个主动过程，而不是核孔扩大的结果。
