Breaking and making of the nuclear envelope

Abstract

During mitosis, a single nucleus gives rise to two nuclei that are identical to the parent nucleus. Mitosis consists of a continuous sequence of events that must be carried out once and only once. Two such important events are the disassembly of the nuclear envelope (NE) during the first stages of mitosis, and its accurate reassembly during the last stages of mitosis. NE breakdown (NEBD) is initiated when maturation-promoting factor (MPF) enters the nucleus and starts phosphorylating nuclear pore complexes (NPCs) and nuclear lamina proteins, followed by NPC and lamina breakdown. Nuclear reassembly starts when nuclear membranes assemble onto the chromatin. This article focuses on the different models of NEBD and reassembly with emphasis on recent data.

Presence of a defect in karyokinesis during megakaryocyte endomitosis

“…LaminA/C is one important component of the nuclear envelope, which is disassembled during the first stage of mitosis and reassembled onto the chromosomes at the last stages of mitosis. 5 During MK endomitosis, the nuclear kinetics is identical to what is observed during a classical mitosis until telophase; nuclear membrane breakdown began in prometaphase of endomitosis, as previously described. 6,7 The nuclear membrane remained disassembled until anaphase and then started to reassemble around the segregated chromosomes at late telophase (Fig.…”

In Vivo Dynamics ofDrosophilaNuclear Envelope Components

“…In vertebrates, cell division leads to complete NE breakdown at the prophase-prometaphase transition. During this "open mitosis," integral membrane proteins of the NE and the soluble subcomplexes of the NPCs redistribute throughout the endoplasmic reticulum and the mitotic cytoplasm (for reviews, see Hetzer et al, 2005;Margalit et al, 2005;Prunuske and Ullman, 2006). In Drosophila and Caenorhabditis elegans embryos, however, the NE only partially disassembles near spindle poles in early mitosis.…”

“…These various aspects of NE and NPC remodeling during mitosis need to be spatially and temporally coordinated with other cell cycle events. Key regulators that contribute to this spatio-temporal coordination are mitotic kinases and phosphatases as well as the small GTPase Ran and the transport receptors of the karyopherin/importin ␤ family (for reviews, see Dasso, 2002;Harel and Forbes, 2004;Hetzer et al, 2005;Margalit et al, 2005; see also Onischenko et al, 2005). In addition, there is growing evidence that NPCs functionally participate in mitosis.…”

“…During cell division, the NE and NPCs are subjected to major rearrangements. However, the extent to which the NE and NPCs disassemble at mitotic entry varies among organisms (for reviews, see Margalit et al, 2005;Prunuske and Ullman, 2006). Unlike in most yeast and fungi, characterized by a "closed mitosis," NE disassembly is required in animal cells to allow spindle microtubule access to chromosomes.…”

“…Accordingly, the term "semi-closed" has been used to describe Drosophila mitosis. In all metazoans, NE and NPC reassembly at mitotic exit is initiated around the two sets of chromosomes in late anaphase, and it continues until late telophase/early G1, leading to the reformation of two daughter nuclei (for reviews, see Hetzer et al, 2005;Margalit et al, 2005;Prunuske and Ullman, 2006;Gorjanacz et al, 2007).…”