Nuclear membrane disassembly and rupture.
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.
Cotter
Laura
L
Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Wilmslow Road, Manchester M20 4BX, UK.
Allen
Terence D
TD
Kiseleva
Elena
E
Goldberg
Martin W
MW
D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D020756:Coatomer Protein / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D007150:Immunohistochemistry; D008677:Metaphase; D008870:Microtubules / Q000737:chemistry; D008938:Mitosis; D008954:Models, Biological; D009685:Nuclear Envelope / Q000737:chemistry*; D022022:Nuclear Pore / Q000378:metabolism; D014981:Xenopus
D020756:Coatomer Protein; D020126:Brefeldin A; D016244:Guanosine 5'-O-(3-Thiotriphosphate)